Patent Publication Number: US-2019193174-A1

Title: Cutting tool

Description:
CROSS REFERENCE 
     This application is the U.S. National Phase under 35 U.S.C. § 371 of International Application No. PCT/JP2017/030549, filed on Aug. 25, 2017, which claims the benefit of Japanese Application No. 2016-195128, filed on Sep. 30, 2016, Japanese Application No. 2016-195016, filed Sep. 30, 2016 and Japanese Application No. 2017-129706, filed on Jun. 30, 2017, the entire contents of each are hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to cutting tools and relates, in particular, to a cutting tool configured to rotate a cutting blade to cut a workpiece. 
     BACKGROUND ART 
     Conventionally, there has been known a cutting tool, such as a miter saw, that includes a motor and a plurality of pulleys. Such a cutting tool transmits rotation of the motor to a cutting blade via a belt looped under tension over the pulleys and thus cuts a workpiece. 
     In this type of cutting tool, rotation of a motor shaft is transmitted to a countershaft via a first-stage transmission mechanism. The first-stage transmission mechanism includes a first pulley attached to the motor shaft, a second pulley attached to the countershaft, and a first belt looped under tension over the first pulley and the second pulley. Rotation of the countershaft is transmitted to an output shaft via a second-stage transmission mechanism, and a cutting blade mounted on the output shaft rotates. The second-stage transmission mechanism includes a third pulley attached to the countershaft, a fourth pulley attached to the output shaft, and a second belt looped under tension over the third pulley and the fourth pulley. In this manner, rotation of a motor can be decelerated and transmitted to the cutting blade without involving a gear. This provides an advantage in that noise traceable to gear meshing does not occur (see Patent Literature 1 below). 
     CITATION LIST 
     Patent Literature 
     [Patent Literature 1] Japanese Patent Application Publication No. 2010-274391 
     SUMMARY OF INVENTION 
     Technical Problem 
     In the above-described cutting tool, however, a load is exerted on each pulley due to belt tension. In particular, a large torque is exerted on the third pulley in transmitting the rotation. Thus, a rotating position of the third pulley fluctuates. This leads to shortcomings in that a loss in transmitting rotation arises and cutting work becomes unstable. 
     Solution to Problem 
     In view of the foregoing, it is an object of the present invention to provide a cutting tool capable of positioning a third pulley with high accuracy. 
     In order to attain the above and other objects, the present disclosure provides a cutting tool including a motor, a first pulley, a countershaft, a second pulley, a third pulley, a first belt, an output shaft, a fourth pulley, a second belt, a first bearing member, a second bearing member, and a support base. The motor has a motor shaft configured to be drivingly rotated. The first pulley is provided at the motor shaft and rotatable integrally with the motor shaft. The countershaft is rotatably driven in accordance with the rotation of the motor shaft. The second pulley and the third pulley are provided at the countershaft. The first belt is looped under tension over the first pulley and the second pulley to transmit the rotation of the motor shaft to the countershaft. The output shaft has a mount portion to which a cutter blade is attachable. The fourth pulley is provided at the output shaft. The second belt is looped under tension over the third pulley and the fourth pulley to transmit the rotation of the countershaft to the output shaft. The first bearing member rotatably supports the countershaft and is positioned between the second pulley and the third pulley. The second bearing member rotatably supports the countershaft and is positioned opposite to the second pulley relative to the third pulley. The support base supports the first bearing member and the second bearing member. The support base has a portion positioned between the second pulley and the third pulley. 
     With this structure, the third pulley can be fixed at a position with high accuracy without increasing numbers of mechanical components, since the countershaft equipped with the second pulley and the third pulley is rotatably supported by the first bearing member and the second bearing member, the first bearing member being positioned between the third pulley and the second pulley and supported by the support base, and the second bearing member being positioned opposite to the second pulley relative to the third pulley and supported to the bearing base. Accordingly, rotational transmission loss in a rotational transmission route from the motor shaft to the cutting blade can be restrained, thereby performing efficient cutting operation. Further, occurrence of fluctuation of rotating position of the pulleys is avoidable in a case of application of large torque to the third pulley. Thus, stabilized cutting operation can be performed. 
     Preferably, the support base includes a first support member and a second support member. The first support member supports the first bearing member and the second pulley. The second support member supports the second bearing member. 
     With this structure, enhanced assembleability can be realized, since each of the first bearing member and the second bearing member is supported by each of support members. 
     Preferably, the cutting tool further includes a third bearing member and a fourth bearing member. The third bearing member is supported to the first support member and rotatably supports the output shaft. The fourth bearing member is supported to the second support member and rotatably supports the output shaft. 
     With this structure, the third pulley and the fourth pulley over which the second belt is looped under tension can be fixed at positions with high accuracy, since the output shaft equipped with the fourth pulley is rotatably supported by the third bearing member and the fourth bearing member those supported to the support base, the fourth pulley being positioned between the third bearing member and the fourth bearing member. Accordingly, rotational transmission loss in a rotational transmission route from the motor shaft to the cutting blade can be further restrained, and occurrence of fluctuation of rotating position of the third pulley and the fourth pulley is avoidable. Thus, stabilized cutting operation can be performed. 
     Preferably, the first pulley has a diameter smaller than that of the second pulley. The third pulley has a diameter smaller than that of the fourth pulley. The first pulley and the second pulley provide a reduction ratio higher than that provided by the third pulley and the fourth pulley. 
     With this structure, torque imparted on the third and fourth pulleys is higher than that imparted on the first and second pulleys, so that a holding mechanism for holding the second belt should provide higher mechanical strength and stability. Here, since the countershaft is rotatably supported by the two bearing members, one bearing member being positioned at one side of the third pulley and the other bearing member being positioned at another side of the third pulley, the third pulley can be stably held even at power transmission at high torque. Thus, generation of vibration due to rattling and fluctuation of the cutting blade can be avoided, rotational transmission loss can be restrained, and efficient and stabilized cutting operation with high accuracy can be performed. 
     Preferably, the second belt is a timing belt. The third pulley and the fourth pulley are timing pulleys. 
     With this structure, the countershaft can be rotatably supported at high accuracy and efficient and stabilized cutting operation can be performed, since occurrence of fluctuation can be restrained in spite of application of high load to the cutting blade. Further, because of the employment of the timing belt and the timing pulleys, enhanced rotational transmission efficiency can be obtained, and damage to the belt can be restrained to thus improve durability of the resultant tool. 
     Preferably, the first belt is a V belt. The first pulley and the second pulley are V pulleys. 
     With this structure, damage to respective components attendant to the rotational transmission can be restrained, because slippage of the V belt over the outer peripheral surface of the V pulleys occurs in case of application of unusual high load to the cutting blade. Accordingly, improved durability of the tool can be obtained. 
     Preferably, the cutting tool further includes a motor, a fifth bearing member, and a sixth bearing member. The motor housing accommodates therein the motor. The fifth bearing member is supported to the motor housing and rotatably supports the motor shaft. The sixth bearing member is supported to the first support member and rotatably supports the motor shaft. 
     With this structure, increase in numbers of mechanical components can be restrained, since the first support member supports not only the first bearing member and the third bearing member but also the sixth bearing member. 
     Preferably, the second support member includes a first support part and a first guide part. The first support part supports the second bearing member. The first guide part is positioned adjacent to the first support part and sloped inward in a radial direction of the countershaft in a direction from an axially inner portion of the countershaft toward the first support part. The second support part supports the fourth bearing member. 
     With this structure, since the first guide part for guiding the second bearing member which rotatably supports the countershaft is positioned adjacent to the first support part, the position of the countershaft can be easily corrected along the first guide part during assembly of the tool even if the countershaft is inadvertently inclined, and the second bearing member mounted on the countershaft can be easily inserted into the first support portion during assembly. Hence, assembly of the tool can be realized with high positional accuracy without any increase in workload and numbers of mechanical parts, and mass production at low cost can be realized. 
     Preferably, the second support member further includes a second guide part. The second guide part is positioned adjacent to the second support part and sloped inward in a radial direction of the output shaft in a direction from an axially inner portion of the output shaft toward the second support part. 
     With this structure, since the second guide part for guiding the fourth bearing member which rotatably supports the output shaft is positioned adjacent to the second support part, the position of the output shaft can be easily corrected along the second guide part during assembly of the tool even if the output shaft is inadvertently inclined, and the fourth bearing member mounted on the output shaft can be easily inserted into the second support part during assembly. Hence, further improvement on positional accuracy and assembly can be realized. 
     Preferably, the second bearing member rotatably supports an end portion of the countershaft. The end portion is opposite to another end portion at which the second pulley is provided. The first guide part is positioned adjacent to an end of the first support part. The end is closer to the second pulley than another end of the first support part is to the second pulley. The second guide part is positioned adjacent to an end of the second support part. The end is farther from the mount portion than another end of the second support part is from the mount portion. 
     With this structure, the part of the countershaft, the part being closer to the second pulley and the part of the output shaft, the part being farther from the mount portion are supported by the first support member through the first bearing member and the third bearing member, respectively. After the second belt is looped over the third pulley and the fourth pulley, the second support member is assembled to the countershaft and the output shaft through the second bearing member and the fourth bearing member, respectively at a part of the countershaft, the part being farther from the second pulley and at a part of the output shaft, the part being closer to the mount portion, respectively. Thus, improved assembleability results. Further, tension imparted on the second belt is lowered by detaching the second support member. Thus, replacement of the second belt by a new belt can be facilitated, to enhance maintenance to the belt. 
     Preferably, the third bearing member rotatably supports an end portion of the output shaft. The end portion is opposite to another end portion at which the mount portion is provided. The first guide part is positioned adjacent to an end of the first support part. The end is farther from the second pulley than another end of the first support part is from the second pulley. The second guide part is positioned adjacent to an end of the second support part. The end is closer to the mount portion than another end of the second support part is to the mount portion. 
     With this structure, the part of the countershaft, the part being farther from the second pulley and the part of the output shaft, the part being closer to the mount portion are supported by the second support member through the second bearing member and the fourth bearing member, respectively. After the second belt is looped under tension over the third pulley and the fourth pulley, the first support member is assembled to the motor shaft, the countershaft, and the output shaft through the sixth bearing member, the first bearing member, and the third bearing member, respectively at a part of the countershaft, the part being closer to the second pulley and at a part of the output shaft, the part being farther from the mount portion, respectively. Thus, a belt between the countershaft and the output shaft can be easily set, and improved assembleability results. 
     Preferably, the second support member includes a first support part and a second support part. The first support part supports the fourth bearing member. The second support part supports the second bearing member. The first support part and the second support part are differently constructed from each other. 
     With this structure, since the second support member is divided into the first support part and the second support part, and each bearing member is supported to each support part. Therefore, each bearing member can be easily fitted in each support part. Therefore, assembleability can further be improved. Further, inclination of the countershaft and the output shaft can be corrected, respectively, and therefore, desirable positional accuracy can be realized. 
     Preferably, the first support member includes a first positioning portion to fix a position of the first support part in a radial direction of the output shaft. Preferably, the first support portion includes a first engagement portion engaging the first positioning portion. 
     With this structure, inclination of the fourth bearing member and the output shaft can be easily and securely corrected, since the first support part supporting the fourth bearing member is fixed to a position with respect to the first support member. 
     Preferably, the first support part includes a second positioning portion to fix a position of the second support part in a radial direction of the countershaft. Preferably, the second support portion includes a second engagement portion engaging the second positioning portion. 
     With this structure, inclination of the second bearing member and the countershaft can be easily and securely corrected, since the second support portion supporting the second bearing member is fixed to a position with respect to the first support portion. Accordingly, a distance between an axis of the countershaft and an axis of the output shaft can be corrected, enabling assembly of the tool with high positional accuracy. 
     Preferably, the first support part extends to cover the countershaft, and is formed with a through-hole facing an outer end portion in an axial direction of the countershaft. The second bearing member is inserted in the through-hole. The second support part supports the second bearing member inserted in the through-hole. 
     With this structure, inclination of the countershaft can be corrected by the second support portion to correct a distance between axes of the countershaft and the output shaft, after inclination of the output shaft is corrected by the first support portion to correct a distance between axes of the third pulley and the fourth pulley. Accordingly, assembleablity of the tool can be improved, enabling the assembly with high positional accuracy. 
     Preferably, the first support part is formed with a notch extending axially inward of the countershaft from an open end of the through-hole, the open end being open to the second support part. The second support part includes a closure portion closing an open end of the notch which is a part of the open end of the through-hole. 
     With this structure, the notch is formed in the first support portion at a position adjacent to the second bearing member. Hence, cooling with external air can be performed even in a case where the output shaft, the countershaft, and the second bearing member, etc. are heated to high temperature due to heat generated at the second belt during operation of the tool. Further, the open end of the notch is closed by the second support portion which is a member different from the first support portion. Therefore, entry of cutting chips can be restrained during cutting operation using the cutting blade. Accordingly, cutting operation would not be interrupted due to high temperature and entry of foreign substances, and workability can be improved, and the tool can provide improved durability. 
     Preferably, the closure portion protrudes outward in a radial direction of the countershaft. 
     With this structure, entry of the cutting chips can further be effectively restrained. 
     Preferably, the cutting tool further includes a fan provided at the motor shaft and rotatable integrally with the motor shaft to generate a cooling air stream. The notch and the closure portion define in combination a port for discharging the cooling air stream therethrough out of the second support member. 
     With this structure, cooling air from the fan passes through interiors of the first and second support members, and is discharged through the port. Therefore, effective cooling to each bearing members, the countershaft, and the output shaft, etc. can be performed, and accordingly, enhanced workability and high durability of the tool can be obtained. 
     Advantageous Effects of Invention 
     In the cutting tool according to the present invention, since the third pulley can be fixed at a position with high accuracy, rotational transmission loss can be restrained, and stabilized cutting operation can be performed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a right side view illustrating a structure of a miter saw according to a generic embodiment of the present invention. 
         FIG. 2  is a left side view illustrating the structure of the miter saw according to the generic embodiment of the present invention. 
         FIG. 3  is a front view illustrating the structure of the miter saw according to the generic embodiment of the present invention. 
         FIG. 4  is a cross-sectional view taken along a line A-A in  FIG. 1 , and particularly illustrating an internal arrangement of the cutting unit in a miter saw according to a first embodiment. 
         FIG. 5  is an exploded perspective view illustrating several components of the cutting unit in the miter saw according to the first embodiment. 
         FIG. 6  is a view illustrating the interior of the cutting unit in the miter saw according to the first embodiment for description of assembling process (part 1). 
         FIG. 7  is a view illustrating the interior of the cutting unit in the miter saw according to the first embodiment for description of assembling process (part 2). 
         FIG. 8  is an exploded perspective view illustrating several components of the cutting unit in the miter saw according to the first embodiment for description of assembling process (part 1). 
         FIG. 9  is a perspective view illustrating the several components of the cutting unit in the miter saw according to the first embodiment for description of assembling process (part 2). 
         FIG. 10  is a cross-sectional view taken along the line A-A in  FIG. 1  and particularly illustrating an internal arrangement of the cutting unit in a miter saw according to a second embodiment. 
         FIG. 11  is a view illustrating the interior of the cutting unit in the miter saw according to the second embodiment for description of assembling process (part 1). 
         FIG. 12  is a view illustrating the interior of the cutting unit in the miter saw according to the second embodiment for description of assembling process (part 2). 
         FIG. 13  is a view illustrating the interior of the cutting unit in the miter saw according to the second embodiment for description of assembling process (part 3). 
         FIG. 14  is a cross-sectional view taken along the line A-A in  FIG. 1  illustrating an interior of a cutting unit in a miter saw according to a third embodiment. 
         FIG. 15  is a cross-sectional view taken along the line A-A in  FIG. 1  illustrating an interior of a cutting unit in a miter saw according to a fourth embodiment. 
         FIG. 16  is an exploded perspective view illustrating several components of the cutting unit in the miter saw according to the fourth embodiment. 
         FIG. 17  is an exploded perspective view illustrating configuration of a gear cover in the miter saw according to the fourth embodiment. 
         FIG. 18  is a view illustrating an interior of the cutting unit in the miter saw according to the fourth embodiment for description of assembling process (part 1). 
         FIG. 19  is a view illustrating the interior of the cutting unit in the miter saw according to the fourth embodiment for description of assembling process (part 2). 
         FIG. 20  is an exploded perspective view illustrating several components of a cutting unit in a miter saw according to a fifth embodiment. 
         FIG. 21  is a cross-sectional view taken along the line A-A in  FIG. 1  and particularly illustrating a flow of cooling air in a miter saw according to the fifth embodiment. 
         FIG. 22  is a cross-sectional view illustrating a cutting unit in a miter saw according to a sixth embodiment. 
         FIGS. 23A and 23B  each are a cross-sectional view of the cutting unit in the miter saw according to the sixth embodiment, in which  FIG. 23A  is a view illustrating a state where an engagement member is separated from a fourth pulley, and  FIG. 23B  is a view illustrating a state where the engagement member engages the fourth pulley. 
         FIGS. 24A and 24B  each are a cross-sectional view of a cutting unit in a miter saw according to a seventh embodiment, in which  FIG. 24A  is a view illustrating a state where an engagement member is separated from a fourth pulley, and  FIG. 24B  is a view illustrating a state where the engagement member engages the fourth pulley. 
         FIGS. 25A and 25B  each are a cross-sectional view of a cutting unit in a miter saw according to an eighth embodiment, in which  FIG. 25A  is a view illustrating a state where an engagement member is separated from a fourth pulley, and  FIG. 25B  is a view illustrating a state where the engagement member engages the fourth pulley. 
         FIGS. 26A to 26D  each are a view illustrating a cutting unit in a miter saw according to a ninth embodiment, in which  FIG. 26A  is a cross-sectional view illustrating a state where an engagement member is separated from a fourth pulley,  FIG. 26B  is a cross-sectional view taken along a line b-b in  FIGS. 26A and 26C  each are a cross-sectional view illustrating a state where the engagement member engages the fourth pulley, and  FIG. 26D  is a cross-sectional view taken along a line d-d in  FIG. 26C . 
         FIGS. 27A to 27C  each are a view illustrating a cutting unit in a miter saw according to a tenth embodiment, in which  FIG. 27A  is a cross-sectional view illustrating a state where an engagement member engages a fourth pulley,  FIG. 27B  is a right side view illustrating a third pulley, a timing belt, a lock mechanism, and the fourth pulley in the engaging state of the engagement member with the fourth pulley, and  FIG. 27C  is a right side view illustrating the third pulley, the timing belt, the lock mechanism, and the fourth pulley in a state of disengagement of the engagement member from the fourth pulley. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be described with reference to the appended drawings. Herein, a case where the present invention is applied to a miter saw will be described as an example. 
     First, a configuration of a miter saw according to an embodiment of the present invention will be described with reference to  FIGS. 1 to 3 .  FIGS. 1, 2, and 3  are, respectively, a right side view, a left side view, and a front view illustrating a configuration of a miter saw  1  according to an embodiment of the present invention. As illustrated in  FIGS. 1 to 3 , the miter saw  1  includes a base unit  2 , a holder  3 , a guide unit  4 , a moving unit  5 , and a cutting unit  6 . The base unit  2  includes a mounting surface  2 A. The cutting unit  6  includes a cutting blade  61 . 
     In the following description, a direction from the base unit  2  to where the guide unit  4  is provided is defined as an upward direction, and its opposite direction is defined as a downward direction. A direction from the holder  3  to where the cutting unit  6  is provided is defined as a frontward direction, and its opposite direction is defined as a rearward direction. A right side of the miter saw  1  as viewed from its rear in  FIG. 1  is defined as a rightward direction, and its opposite direction is defined as a leftward direction. 
     As illustrated in  FIGS. 1 to 3 , the base unit  2  includes a base  21 , a turntable  22 , and a fence  23 . 
     The base  21  is made of metal. The base  21  can be placed on a floor surface. The turntable  22  is made of metal. The turntable  22  is coupled to the base  21  via a pivot shaft that is orthogonal to an upper surface of the turntable  22 . The turntable  22  is disposed such that its upper surface is substantially flush with an upper surface of the base  21 . When a workpiece is to be cut, the mounting surface  2 A where the workpiece can be placed is defined by the upper surface of the base  21  and the upper surface of the turntable  22 . A groove (not illustrated) is formed in the turntable  22  and the base  21 . The cutting blade  61  can enter the groove when the cutting unit  6  is lowered in operation. 
     The fence  23  is provided on the base  21 . As illustrated in  FIG. 3 , the fence  23  includes a right fence  23 A and a left fence  23 B. The right fence  23 A and the left fence  23 B include a pressing surface  23   a . The pressing surface  23   a  is substantially orthogonal to the mounting surface  2 A. When a workpiece is to be cut, one surface of the workpiece is made to abut the pressing surface  23   a  of the fence  23 . Thus, the workpiece can be cut stably. 
     An operating portion  24  is provided on a front portion of the turntable  22 . The operating portion  24  is operated by a user when the turntable  22  is turned and its turning position is fixed. A tilting shaft  25  and a projection  26  are provided on a rear portion of the turntable  22 . The tilting shaft  25  is provided such that the tilting shaft  25  extends parallel to a side surface of the cutting blade  61  in a frontward/rearward direction and a center axis of the tilting shaft  25  substantially coincides with the upper surface of the turntable  22 . As illustrated in  FIGS. 1 and 2 , the projection  26  projects upward. An elongated hole  26   a  is formed in the projection  26 . The elongated hole  26   a  has a circular arc shape with its center lying on the center axis of the tilting shaft  25 . 
     The holder  3  is erected upward at the rear portion of the turntable  22 . A lower portion of the holder  3  is pivotable about an axis of the tilting shaft  25 . Thus, the holder  3  can tilt in a rightward/leftward direction relative to the turntable  22 . A threaded hole (not illustrated) is formed in the holder  3  at a position that coincides with the position of the elongated hole  26   a . A clamp lever  31  is screwed into this threaded hole. 
     The guide unit  4  includes a first rod  41 , a second rod  42 , and a coupling member  43 . The first rod  41  and the second rod  42  are each formed of a high-rigidity material, such as a pipe material. The first rod  41  extends in a direction that is parallel to the mounting surface  2 A of the base unit  2  and that is orthogonal to an axis of rotation of the cutting blade  61 . The second rod  42  extends parallel to the first rod  41 . The second rod  42  is located under the first rod  41 . The first rod  41  and the second rod  42  have substantially equal lengths and are shorter than the turntable  22  in its lengthwise direction (frontward/rearward direction). The coupling member  43  is attached to front end portions of the first rod  41  and the second rod  42 . The first rod  41  and the second rod  42  are configured to tilt in the rightward/leftward direction along with the holder  3  as the holder  3  tilts in the rightward/leftward direction relative to the turntable  22 . 
     The moving unit  5  pivotally movably supports the cutting unit  6 , in a direction toward and away from the base unit  2 . The moving unit  5  is supported by the guide unit  4  and is slidably movable in the frontward/rearward direction. As illustrated in  FIG. 2 , the moving unit  5  includes a slide portion  51  and a cutting unit support  52 . 
     The slide portion  51  is so provided as to extend over the first rod  41  and the second rod  42 . The first rod  41  and the second rod  42  penetrate the slide portion  51 . The slide portion  51  is configured to slide on the first rod  41  and the second rod  42  between the holder  3  and the coupling member  43 . The cutting unit support  52  is formed integrally with the slide portion  51 . As illustrated in  FIGS. 1 and 2 , a pivot shaft  52 A is fixed to the cutting unit support  52 . The pivot shaft  52 A extends in a direction (rightward/leftward direction) orthogonal to an axial direction (frontward/rearward direction) of the first rod  41  and the second rod  42 . The cutting unit support  52  pivotally movably supports the cutting unit  6  about an axis of the pivot shaft  52 A in the direction toward and away from the base unit  2 . 
     As will be described later, the cutting unit  6  is partially covered by a housing and a gear cover  66 . The housing includes a saw cover  62 , a protective cover  63 , a motor housing  64 , and a gear housing  650 . The cutting unit  6  is configured to pivot as the gear cover  66  pivots about an axis of the pivot shaft  52 A. 
     As illustrated in  FIG. 1 , an outer periphery of the cutting blade  61  is partially covered by the saw cover  62 . The protective cover  63  is pivotally provided inside the saw cover  62 . The protective cover  63  is configured to cover a portion of the outer periphery of the cutting blade  61  that projects out of the saw cover  62 . As illustrated in  FIG. 1 , the protective cover  63  is located at a position where the protective cover  63  covers the portion of the outer periphery of the cutting blade  61  that projects out of the saw cover  62 , in a state where the cutting unit  6  is being pivoted upward. In addition, the protective cover  63  is housed inside the saw cover  62  by a link mechanism (not illustrated) and located at a position where the protective cover  63  allows the portion of the outer periphery of the cutting blade  61  that projects out of the saw cover  62  to be exposed, in a state where the cutting unit  6  is being pivoted downward (not illustrated). 
     A handle portion  67  is integrally provided on the motor housing  64 . The handle portion  67  is located in a plane extended from the side surface of the cutting blade  61 . A switch  67 A is provided on the handle portion  67 . The switch  67 A is configured to control driving of a motor (described later) housed inside the motor housing  64 . 
     Next, a detailed configuration of the cutting unit  6  of the miter saw  1  according to a first embodiment will be described with reference to  FIG. 4 .  FIG. 4  illustrates an inside of the cutting unit  6  of the miter saw  1  according to the first embodiment.  FIG. 4  is a sectional view taken along an A-A plane indicated in  FIG. 1 . In  FIG. 4 , illustration of the saw cover  62  and the protective cover  63  is omitted. 
     As illustrated in  FIG. 4 , the cutting unit  6  includes a motor  68 , a transmission mechanism unit  60 , and the cutting blade  61 . The cutting unit  6  is partially covered by the housing. 
     The housing for the cutting unit  6  includes the saw cover  62 , the protective cover  63 , the motor housing  64 , and the gear housing  650 . The motor housing  64  has a substantially cylindrical shape extending in the rightward/leftward direction. As illustrated in  FIGS. 1 and 4 , a slit-shaped intake port  64   a  is formed in a right side surface of the motor housing  64 . The gear housing  650  is coupled to a left side opening of the motor housing  64 . The gear housing  650  has a substantially U-like shape that extends leftward in a direction parallel to the cutting blade  61  (the A-A direction indicated in  FIG. 1 ) and that opens at a right side end. 
     A gear case  65  is provided inside the gear housing  650 . The gear case  65  is coupled to the left side opening of the motor housing  64 . The gear case  65  is so shaped as to extend in the direction parallel to the cutting blade  61  (the A-A direction indicated in  FIG. 1 ). The gear cover  66  has a cylindrical shape extending in the rightward/leftward direction and having a substantially elliptical cross-section. The gear cover  66  is coupled to the gear case  65 . The shapes of the gear case  65  and the gear cover  66  will be described later in detail. 
     The motor  68  is housed inside the motor housing  64 . The motor  68  includes a motor body  68 A, a motor shaft  68 B, a fan  68 C, and a commutator  68 D. The motor shaft  68 B has a substantially columnar shape. The motor shaft  68 B is so disposed as to extend in the rightward/leftward direction of the motor body  68 A. The motor shaft  68 B is rotatably supported by the motor housing  64  via a bearing  69   a  and rotatably supported by the gear case  65  via a bearing  69   b . A left end portion of the motor shaft  68 B projects outward (leftward) out of the gear case  65 . 
     The fan  68 C is fixed to the motor shaft  68 B at a left side of the motor body  68 A. The fan  68 C is configured to corotate with the motor shaft  68 B. The fan  68 C is configured to suck in an outside air through the intake port  64   a  of the motor housing  64  and discharge an air through a discharge port (described later) formed in the gear case  65 . Thus, the fan  68 C is configured to cool the motor body  68 A, the commutator  68 D, and so on. 
     The bearing  69   a  is a ball bearing made of a steel material. The bearing  69   a  is supported by the motor housing  64  and rotatably supports a right end portion of the motor shaft  68 B. The bearing  69   a  is an example of a fifth bearing member in the present invention. The bearing  69   b  is a ball bearing made of a steel material. The bearing  69   b  is supported by the gear case  65  and rotatably supports the motor shaft  68 B on a left side of the fan  68 C. The bearing  69   b  is an example of a sixth bearing member in the present invention. 
     The transmission mechanism unit  60  is configured to transmit rotation of the motor  68  to the cutting blade  61  in a two-stage belt system. As illustrated in  FIG. 4 , the transmission mechanism unit  60  includes a first pulley  601 , a countershaft  602 , a second pulley  603 , a first belt  604 , a third pulley  605 , a spindle  606 , a fourth pulley  607 , and a second belt  608 . Among the above, the first pulley  601 , the second pulley  603 , and the first belt  604  constitute a first-stage transmission mechanism; and the third pulley  605 , the fourth pulley  607 , and the second belt  608  constitute a second-stage transmission mechanism. 
     The first pulley  601  is a V-pulley. The first pulley  601  has a cylindrical shape extending in the rightward/leftward direction. A groove extending in a circumferential direction is formed in an outer peripheral surface of the first pulley  601 . The first pulley  601  is fixed to the left end portion of the motor shaft  68 B at the outside (left side) of the gear case  65 . The first pulley  601  is configured to corotate with the motor shaft  68 B. The first pulley  601  is an example of a first pulley in the present invention. 
     The countershaft  602  has a substantially columnar shape. The countershaft  602  is so disposed as to extend substantially parallel to the motor shaft  68 B in the rightward/leftward direction. The countershaft  602  is rotatably supported by the gear case  65  via a bearing  70   a  and rotatably supported by the gear cover  66  via a bearing  70   b . A left end portion of the countershaft  602  projects outward (leftward) out of the gear case  65 . The countershaft  602  is an example of a countershaft in the present invention. 
     The bearing  70   a  is a ball bearing made of a steel material. The bearing  70   a  is supported by the gear case  65  and rotatably supports the countershaft  602 . The bearing  70   a  is an example of a first bearing member in the present invention. The bearing  70   b  is a ball bearing made of a steel material. The bearing  70   b  is supported by the gear cover  66  and rotatably supports a right end portion of the countershaft  602 . The bearing  70   b  is an example of a second bearing member in the present invention. 
     The second pulley  603  is a V pulley, and has a cylindrical shape extending in the rightward/leftward direction. A groove extending in a circumferential direction is formed in an outer peripheral surface of the second pulley  603 . The second pulley  603  has an outer diameter greater than an outer diameter of the first pulley  601 . The second pulley  603  is fixed to the left end portion of the countershaft  602  via a fastener  609  at the outside (left side) of the gear case  65 . The second pulley  603  is configured to corotate with the countershaft  602 . The second pulley  603  is an example of a second pulley in the present invention. 
     The first belt  604  is an endless belt made of resin into an endless form. The first belt  604  is a V-belt having a groove extending in a longitudinal direction formed in an inner peripheral surface. An upper portion of the first belt  604  rests on an outer periphery of the first pulley  601 . A lower portion of the first belt  604  rests on an outer periphery of the second pulley  603 . Thus, the first belt  604  is looped under tension over the first pulley  601  and the second pulley  603 . The first belt  604  is formed to have a perimeter smaller than a stretching distance between the first pulley  601  and the second pulley  603 . The first belt  604  is looped under tension over the first pulley  601  and the second pulley  603  in a state where the first belt  604  is tensioned at a stretch rate of greater than 1. The first belt  604  is configured to corotate with the first pulley  601  and the second pulley  603  through a frictional force produced between the inner peripheral surface of the first belt  604  and the outer peripheral surfaces of the first pulley  601  and the second pulley  603 . The first belt  604  is an example of a first belt in the present invention. 
     The third pulley  605  is a timing pulley. The third pulley  605  has a cylindrical shape extending in the rightward/leftward direction. Concavities and convexities of a gear shape are formed in an outer peripheral surface of the third pulley  605 . The third pulley  605  has an outer diameter smaller than the outer diameter of the second pulley  603 . The third pulley  605  is press-fitted and fixed on the countershaft  602  rightward to a middle portion of the countershaft  602 . The third pulley  605  is configured to corotate with the countershaft  602 . The third pulley  605  is an example of a third pulley in the present invention. 
     The spindle  606  is so disposed as to extend in the rightward/leftward direction substantially parallel to the motor shaft  68 B and the countershaft  602 . The spindle  606  is rotatably supported by the gear case  65  via a bearing  71   a  and rotatably supported by the gear cover  66  via a bearing  71   b . A mounting portion  606 A is provided at a right end portion of the spindle  606 . The cutting blade  61  is to be mounted to the mounting portion  606 A. The mounting portion  606 A projects outward (rightward) out of the gear cover  66 . The spindle  606  is an example of an output shaft in the present invention. 
     The bearing  71   a  is a ball bearing made of a steel material. The bearing  71   a  is supported by the gear case  65  and rotatably supports a left end of the spindle  606 . The bearing  71   a  is an example of a third bearing member in the present invention. The bearing  71   b  is a ball bearing made of a steel material. The bearing  71   b  is supported by the gear cover  66  and rotatably supports the spindle  606 . The bearing  71   b  is an example of a fourth bearing member in the present invention. 
     The fourth pulley  607  is a timing pulley and has a cylindrical shape extending in rightward/leftward direction. Concavities and convexities of a gear shape are formed in an outer peripheral surface of the fourth pulley  607 . The fourth pulley  607  has an outer diameter greater than the outer diameter of the third pulley  605 . The fourth pulley  607  is press-fitted and fixed on the spindle  606  leftward to a middle portion of the spindle  606 . The fourth pulley  607  is configured to corotate with the spindle  606 . The fourth pulley  607  is an example of a fourth pulley in the present invention. 
     The second belt  608  is an endless belt made of resin into an endless form. The second belt  608  is a timing belt having concavities and convexities of a gear shape formed in an inner peripheral surface. An upper portion of the second belt  608  rests on an outer periphery of the third pulley  605 . A lower portion of the second belt  608  rests on an outer periphery of the fourth pulley  607 . Thus, the second belt  608  is looped under tension over the third pulley  605  and the fourth pulley  607 . At this point, the concavities and convexities in the inner peripheral surface of the second belt  608  mesh with concavities and convexities in the outer peripheral surfaces of the third pulley  605  and the fourth pulley  607 . Thus, rotation of the third pulley  605  is transmitted to the fourth pulley  607  via the second belt  608 , and the fourth pulley  607  rotates. The second belt  608  is formed to have a perimeter smaller than a stretching distance between the third pulley  605  and the fourth pulley  607 . The second belt  608  is looped under tension over the third pulley  605  and the fourth pulley  607  in a state where the second belt  608  is tensioned at a stretch rate of greater than 1. The second belt  608  is an example of a second belt in the present invention. 
     The cutting blade  61  has a substantially circular disc shape. The cutting blade  61  is fixed to the mounting portion  606 A of the spindle  606  via a pair of flanges  610  and a fastener  611 . The cutting blade  61  is so supported as to be rotatable along with the spindle  606 . 
     Next, an operation in which rotation of the motor  68  is transmitted to the cutting blade  61  will be described. 
     Upon a user pressing down the switch  67 A on the handle portion  67 , the motor  68  starts running, and the motor shaft  68 B corotates with the first pulley  601 . In conjunction with this rotation, the first belt  604  looped under tension over the first pulley  601  corotates with the first pulley  601  through a frictional force, and the second pulley  603  having the first belt  604  looped under tension thereover corotates with the first belt  604  through a frictional force. Specifically, the first belt  604  transmits rotation of the motor shaft  68 B and the first pulley  601  to the second pulley  603 , and the second pulley  603  is caused to rotate along with the countershaft  602 . Since the second pulley  603  has a diameter greater than that of the first pulley  601 , rotation of the motor shaft  68 B is decelerated and transmitted to the countershaft  602 . In other words, the first-stage transmission mechanism including the first pulley  601 , the second pulley  603 , and the first belt  604  decelerates the rotation of the motor shaft  68 B and transmits the decelerated rotation to the countershaft  602 . 
     The second pulley  603  corotates with the countershaft  602  and the third pulley  605  fixed to the countershaft  602  at the same rotation speed. In conjunction with this rotation, the second belt  608  that meshes with the third pulley  605  is rotated by the third pulley  605 , and the fourth pulley  607  that meshes with the second belt  608  is rotated by the second belt  608 . Specifically, the second belt  608  transmits rotation of the countershaft  602  and the third pulley  605  to the fourth pulley  607 , and the fourth pulley  607  is caused to rotate along with the spindle  606 . Since the fourth pulley  607  has a diameter greater than that of the third pulley  605 , rotation of the countershaft  602  is decelerated and transmitted to the spindle  606 . In other words, the second-stage transmission mechanism including the third pulley  605 , the fourth pulley  607 , and the second belt  608  decelerates the rotation of the countershaft  602  and transmits the decelerated rotation to the spindle  606 . 
     The fourth pulley  607  corotates with the spindle  606 . In conjunction with this rotation, the cutting blade  61  mounted to the mounting portion  606 A of the spindle  606  corotates with the spindle  606  at the same rotation speed. In other words, rotation of the motor shaft  68 B is decelerated in two stages by the two-stage transmission mechanism, and the decelerated rotation is transmitted to the cutting blade  61 . 
     In the miter saw  1  according to the present embodiment, an enlarging ratio of the diameter of the fourth pulley  607  relative to the diameter of the third pulley  605  is smaller than an enlarging ratio of the diameter of the second pulley  603  relative to the diameter of the first pulley  601  so that a reduction ratio of the first-stage transmission mechanism is greater than a reduction ratio of the second-stage transmission mechanism. 
     Next, the shape of the gear case  65  of the miter saw  1  according to the first embodiment will be described in detail with reference to  FIGS. 4 and 5 .  FIG. 5  is an exploded perspective view illustrating a configuration of a portion of the cutting unit  6  of the miter saw  1  according to the first embodiment. 
     The gear case  65  is configured to cover a left side surface of the cutting unit  6  and support the bearing  69   b , the bearing  70   a , and the bearing  71   a . As illustrated in  FIG. 5 , the gear case  65  is formed integrally by a gear case  65 A and a gear case  65 B. The gear case  65  is an example of a first support member in the present invention. 
     The gear case  65 A is formed in one piece of a metal steel material. The gear case  65 A has a substantially columnar shape. The gear case  65 A includes a protrusion  651 . The protrusion  651  projects leftward from a center portion of the gear case  65 A. The protrusion  651  has a cylindrical shape extending in the rightward/leftward direction. The protrusion  651  includes a support part  651 A. The support part  651 A defines an inner peripheral surface of the protrusion  651 . A right end portion of the support part  651 A is open. A left end portion of the support part  651 A has a circular ring shape with an opening formed at its center portion. As illustrated in  FIG. 4 , the bearing  69   b  is disposed inside the support part  651 A. An inner diameter of the support part  651 A is substantially equal to an outer diameter of the bearing  69   b . The bearing  69   b  is fitted inside the support part  651 A and fixed therein. The motor shaft  68 B projects leftward through a left side opening of the protrusion  651 . The first pulley  601  is attached to the projecting portion of the motor shaft  68 B. As illustrated in  FIG. 5 , a plurality of discharge ports  65   a  is formed in a periphery of the opening of the gear case  65 A. 
     The gear case  65 B has substantially elliptical right and left side surfaces. A groove  654  is formed in the right side surface at its center portion. The groove  654  has a substantially elliptical cross-section. Two protrusions  652  and  653  are disposed inside the groove  654 . 
     The protrusion  652  is disposed toward the gear case  65 A. The protrusion  652  has a cylindrical shape extending in the rightward/leftward direction. The protrusion  652  includes a support  652 A. The support  652 A defines an inner peripheral surface of the protrusion  652 . Right and left ends of the support  652 A are open. As illustrated in  FIG. 4 , the bearing  70   a  is disposed inside the support  652 A. An inner diameter of the support  652 A is substantially equal to an outer diameter of the bearing  70   a . The bearing  70   a  is fitted inside the support  652 A and fixed therein. 
     The protrusion  653  is aligned with the protrusion  652  in a direction of a major axis of the groove  654 . The protrusion  653  has a cylindrical shape extending in the rightward/leftward direction. The protrusion  653  includes a support  653 A. The support  653 A defines an inner peripheral surface of the protrusion  653 . A right end portion of the support  653 A is open. A left end portion of the support  653 A is covered by the left side surface of the gear case  65 B. As illustrated in  FIG. 4 , the bearing  71   a  is disposed inside the support  653 A. An inner diameter of the support  653 A is substantially equal to an outer diameter of the bearing  71   a . The bearing  71   a  is fitted inside the support  653 A and fixed therein. 
     Next, the shape of the gear cover  66  of the miter saw  1  according to the first embodiment will be described in detail with reference to  FIGS. 4 to 7 .  FIGS. 6 and 7  each illustrate the inside of the cutting unit  6  of the miter saw  1  according to the first embodiment.  FIGS. 6 and 7  are illustrations for describing an assembly process. 
     As illustrated in  FIG. 4 , the gear cover  66  is disposed on a right side of the gear case  65 . The gear cover  66  supports the bearing  70   b  and the bearing  71   b . The gear cover  66  is an example of a second support member in the present invention. The gear case  65  and the gear cover  66  are an example of a support base in the present invention. 
     As illustrated in  FIG. 5 , the gear cover  66  has a cylindrical shape having a substantially elliptical cross-section. The gear cover  66  is so disposed as to cover the groove  654  in the gear case  65 . 
     As illustrated in  FIGS. 4 and 6 , a three-step groove  661  is formed inside the gear cover  66 . The groove  661  includes a lid  661 A, a support  661 B, and a guide  661 C that are arrayed in the rightward/leftward direction. 
     The lid  661 A has a cylindrical shape extending in the rightward/leftward direction. A left end portion of the lid  661 A is open. A right end portion of the lid  661 A is covered by a right side surface of the gear cover  66 . The lid  661 A has an inner diameter greater than an outer diameter of the countershaft  602  and an inner diameter of the bearing  70   b.    
     The support part  661 B is connected adjacent to a left side of the lid  661 A. The support part  661 B has a cylindrical inner peripheral surface extending in the rightward/leftward direction. Right and left ends of the support part  661 B are open. The support part  661 B has an inner diameter that is greater than the inner diameter of the lid  661 A and that is substantially equal to an outer diameter of the bearing  70   b . As illustrated in  FIG. 4 , the bearing  70   b  is disposed inside the support  661 B. The support part  661 B is an example of a first support part in the present invention. 
     The guide  661 C is connected adjacent to a left side of the support  661 B. The guide  661 C has a tapered inner peripheral surface extending in the rightward/leftward direction. Right and left ends of the guide  661 C are open. The guide  661 C is inclined inward in a radial direction of the countershaft  602  along a direction toward the support part  661 B and the bearing  70   b , that is, along a direction toward the right side, and a diameter of the guide  661 C thus decreases. As illustrated in  FIG. 7 , an inner diameter Φ 1  of the guide  661 C at its left end portion is greater than the outer diameter of the bearing  70   b . The guide  661 C is an example of a first guide part in the present invention. 
     As illustrated in  FIG. 5 , the gear cover  66  is provided with a protrusion  662 . The protrusion  662  projects outward (rightward). The protrusion  662  has a cylindrical shape extending in the rightward/leftward direction. The protrusion  662  includes a support part  662 A and a guide  662 B. 
     The support part  662 A has a cylindrical inner peripheral surface extending in the rightward/leftward direction. A left end portion of the support part  662 A is open, and a right end portion of the support part  662 A has a circular ring shape with an opening  662   a  formed at its center portion. The support part  662 A is formed such that the opening  662   a  has an inner diameter greater than an outer diameter of the spindle  606 . The inner peripheral surface of the support part  662 A has an inner diameter substantially equal to an outer diameter of the bearing  71   b . As illustrated in  FIG. 4 , the bearing  71   b  is disposed inside the support  662 A. The support part  662 A is an example of a second support part in the present invention. 
     The guide  662 B is connected adjacent to a left side of the support  662 A. The guide  662 B has a tapered inner peripheral surface extending in the rightward/leftward direction. Right and left ends of the guide  662 B are open. The guide  662 B is inclined inward in a radial direction of the spindle  606  along a direction toward the support part  662 A and the bearing  71   b , that is, along a direction toward the right side, and a diameter of the guide  662 B thus decreases. As illustrated in  FIG. 6 , an inner diameter  12  of the guide  662 B at its left end portion is greater than the outer diameter of the bearing  71   b . The guide  662 B is an example of a second guide part in the present invention. 
     Next, a process of assembling the cutting unit  6  of the miter saw  1  according to the first embodiment will be described with reference to  FIGS. 4 to 9 .  FIGS. 8 and 9  are, respectively, an exploded perspective view and a perspective view illustrating a configuration of a portion of the cutting unit  6  of the miter saw  1  according to the first embodiment.  FIGS. 8 and 9  are illustrations for describing an assembly process. 
     The third pulley  605  is press-fitted and fixed onto an outer surface of the countershaft  602  at a predetermined position on the right side of the middle portion of the countershaft  602 . At a later point, the bearing  70   b  is fitted and fixed onto the outer surface of the countershaft  602  at a predetermined position on the right side of the third pulley  605 . 
     The fourth pulley  607  is press-fitted and fixed onto an outer surface of the spindle  606  at a predetermined position on the left side of the middle portion of the spindle  606 . The bearing  71   a  is fitted and fixed onto the outer surface of the spindle  606  at a predetermined position on the left side of the fourth pulley  607 . The bearing  71   b  is fitted and fixed onto the outer surface of the spindle  606  at a predetermined position on the right side of the fourth pulley  607 . The fourth pulley  607 , the bearing  71   a , and the bearing  71   b  may be fixed to the spindle  606  in any order. 
     The motor  68  is housed in the motor housing  64 . The bearing  69   a  is fixed to the right end portion of the motor shaft  68 B of the motor  68 . As illustrated in  FIG. 6 , the bearing  69   a  is fixed at a predetermined position inside the motor housing  64 . The bearing  69   b  is also fitted and fixed onto an outer surface of the motor shaft  68 B at a predetermined position on the left side of the fan  68 C. 
     In the first embodiment, the motor shaft  68 B, the countershaft  602 , and the spindle  606  are attached to the gear case  65  via the bearing  69   b , the bearing  70   a , and the bearing  71   a . Then, the gear cover  66  is attached to the gear case  65 . 
     As will be illustrated below, the bearing  69   b  and the bearing  71   a  are attached to the gear case  65  from the right side, and the bearing  70   a  is attached to the gear case  65  from the left side. The bearings  69   b ,  70   a , and  71   a  may be attached in any order. 
     The motor shaft  68 B with the bearing  69   b  attached thereto is fitted into the protrusion  651  of the gear case  65 A from the right side. The bearing  69   b  is supported with its outer peripheral portion abutting the support part  651 A. At this point, the left end portion of the motor shaft  68 B projects leftward through the left side opening of the protrusion  651 . Alternatively, the motor shaft  68 B may be inserted and attached from the right side after the bearing  69   b  is fixed to the support part  651 A. 
     The countershaft  602  is fitted into the protrusion  652  of the gear case  65 B from the right side. The countershaft  602  is fitted and fixed into the bearing  70   a  fixed to the gear case  65  at a predetermined position on the left side of the third pulley  605  on the countershaft  602 . The bearing  70   b  is supported with its outer peripheral portion abutting the support  652 A of the gear case  65 . At this point, the left end portion of the countershaft  602  projects leftward through a left side opening of the protrusion  652 . Alternatively, the bearing  70   a  may be fitted on the outer surface of the countershaft  602  and fixed to the support  652 A after the countershaft  602  is inserted into the support  652 A. 
     The spindle  606  with the bearing  71   a  attached thereto is fitted into the protrusion  653  of the gear case  65 B from the right side. The bearing  71   a  is supported with its outer peripheral portion abutting the support  653 A. Alternatively, the spindle  606  may be inserted and attached from the right side after the bearing  71   a  is fixed to the support  653 A. 
     As described above, the bearing  69   b , the bearing  70   a , and the bearing  71   a  are fixed to the gear case  65 , and the left sides of the motor shaft  68 B, the countershaft  602 , and the spindle  606  are positioned relative to the gear case  65 . At this point, the position of the third pulley  605  fixed to the countershaft  602  substantially coincides with the position of the fourth pulley  607  fixed to the spindle  606  in the rightward/leftward direction. 
     Next, as illustrated in  FIGS. 6 and 8 , the second belt  608  is looped under tension over the third pulley  605  and the fourth pulley  607 . The second belt  608  is attached from the right end sides of the countershaft  602  and the spindle  606  in a state where the second belt  608  is looped under tension at a stretch rate of greater than 1. The second belt  608  is looped under tension over the outer peripheral surface of the third pulley  605  and the outer peripheral surface of the fourth pulley  607 . At this point, due to the tension of the second belt  608 , the unfixed right end portion of the countershaft  602  tilts in a direction approaching the spindle  606 , and the unfixed right end portion of the spindle  606 , that is, the side where the mounting portion  606 A is provided tilts in a direction approaching the countershaft  602 . 
     In this tilted state, the gear cover  66  is attached to the gear case  65  from the right side. The bearing  70   b  and the bearing  71   b  may be attached to the gear cover  66  from the left side, and then the gear cover  66  may be attached to the gear case  65 . In the case described herein, however, as illustrated  FIG. 6 , the bearing  70   b  and the bearing  71   b  are attached to the countershaft  602  and the spindle  606 , respectively, and then the gear cover  66  is attached to the gear case  65 . 
     The gear cover  66  is brought closer, from the right side, to the countershaft  602  tilted in a direction approaching the spindle  606  and the spindle  606  tilted in a direction approaching the countershaft  602  upon the second belt  608  having been looped under tension thereover. At this point, firstly, the spindle  606  extending further rightward than the countershaft  602  enters the guide  662 B. As illustrated in  FIG. 6 , the inner diameter  12  of the left side opening of the guide  662 B is greater than the outer diameter of the bearing  71   b . Thus, the spindle  606  with the bearing  71   b  attached thereto can enter the guide  662 B while remaining in a tilted state. 
     The diameter of the guide  662 B decreases along the rightward direction. The spindle  606  is guided by the abutment of a portion of the outer peripheral surface of the bearing  71   b  with the inner peripheral surface of the guide  662 B, the portion of the outer peripheral surface being closer to the countershaft  602  than a remaining portion thereof is to the countershaft  602 . In other words, as illustrated in  FIG. 7 , the gear cover  66  guides the bearing  71   b  and the spindle  606  in a direction away from the countershaft  602  along the inclination of the inner peripheral surface of the guide  662 B. Being guided by the guide  662 B, the spindle  606  has its tilted state corrected, and the bearing  71   b  enters the support  662 A. 
     In a similar manner, when the gear cover  66  approaches from the right side, the countershaft  602  enters the guide  661 C. As illustrated in  FIG. 7 , the inner diameter (Di of the left side opening of the guide  661 C is greater than the outer diameter of the bearing  70   b . Thus, the countershaft  602  with the bearing  70   b  attached thereto can enter the guide  661 C while remaining in a tilted state. 
     As in the guide  662 B, the diameter of the guide  661 C decreases along the rightward direction. The countershaft  602  is guided by the abutment of a portion of the outer peripheral surface of the bearing  70   b  with the inner peripheral surface of the guide  661 C, the portion of the outer peripheral surface being closer to the spindle  606  than a remaining portion thereof is to the spindle  606 . Specifically, the gear cover  66  guides the bearing  70   b  and the countershaft  602  in a direction away from the spindle  606  along the inclination of the inner peripheral surface of the guide  661 C. Being guided by the guide  661 C, the countershaft  602  has its tilted state corrected, and the bearing  70   b  enters the support  661 B. 
     The bearing  71   b  is fixed inside the support  662 A, and the bearing  70   b  is fixed inside the support  661 B. As illustrated in  FIG. 9 , the gear cover  66  abuts the right side surface of the gear case  65 . Then, the gear cover  66  is fixed to the gear case  65  with a fastener, such as a screw. At this point, as illustrated in  FIGS. 4 and 9 , the mounting portion  606 A of the spindle  606  projects rightward through the opening  662   a  in the protrusion  662 . 
     Next, the first pulley  601 , the second pulley  603 , and the first belt  604  are attached. The first pulley  601 , the second pulley  603 , and the first belt  604  may be attached before the gear cover  66  is attached. In addition, the first pulley  601  and the second pulley  603  may be attached in either order. 
     The first pulley  601  is fitted and fixed onto an outer surface of the left end portion of the motor shaft  68 B projecting out of the gear case  65 . The second pulley  603  is fitted, via a washer  72 , onto an outer surface of the left end portion of the countershaft  602  projecting out of the gear case  65 . The second pulley  603  is fixed with the fastener  609 . Then, the first belt  604  is looped under tension over the first pulley  601  and the second pulley  603 . The first pulley  601  is attached from the left side in a state where the first belt  604  is looped under tension at a stretch rate of greater than 1. The first belt  604  is looped under tension over the outer peripheral surface of the first pulley  601  and the outer peripheral surface of the second pulley  603 . 
     The cutting blade  61  is mounted to the mounting portion  606 A of the spindle  606 . The pair of flanges  610  is attached to the cutting blade  61 . A projection  611 A of the fastener  611  is inserted into a hole provided at a center of the cutting blade  61 . Thus, the cutting blade  61  is fixed to the mounting portion  606 A. 
     As described thus far, the miter saw  1  according to the present embodiment allows the third pulley  605  to be positioned with high accuracy without any specialized component being provided since the bearing  70   a  and the bearing  70   b  supporting the countershaft  602  are disposed on the left and the right of the third pulley  605 . The third pulley  605  is a component on which a particularly large torque is exerted in the transmission mechanism unit  60 . Thus, this improvement in the positioning accuracy of the third pulley  605  makes it possible to suppress a loss in transmitting rotation in the transmission mechanism unit  60  and allows cutting work to be carried out efficiently. Even in a case where a large torque is exerted on the third pulley  605 , fluctuation of the third pulley  605  can be prevented, and stable cutting work can be carried out with high accuracy. The bearing  70   a  is supported by the gear case  65 , and the bearing  70   b  is supported by the gear cover  66 . Thus, assembleability can be improved. Furthermore, a portion of the gear case  65  is disposed between the second pulley  603  and the third pulley  605 . Thus, the second pulley  603  can be attached from the outside of the gear case  65 , and assembleability and maintenance to the second pulley  603  can be improved. 
     Due to the tension (pulling) of the V-belt (first belt  604 ), a load is exerted on the countershaft  602  upward (in a direction approaching the motor shaft  68 B) at a portion on the left side of the bearing  70   a . In addition, due to the tension (pulling) of the timing belt (second belt  608 ), a load is exerted on the countershaft  602  downward (in a direction approaching the spindle  606 ) at a portion on the right side of the bearing  70   a . In other words, the countershaft  602  is pulled upward and downward (in opposite directions) at the left side and the right side, respectively. However, the bearing  70   a  is disposed between the two locations where the loads are exerted. Thus, the countershaft  602  can be supported more stably. Furthermore, the countershaft  602  is supported entirely on the right side of the second pulley  603 . Thus, the number of components to be provided on the left side of the second pulley  603  can be reduced, and the size can be reduced. 
     In a similar manner, the bearing  71   a  and the bearing  71   b  that support the spindle  606  are supported by the gear case  65  and the gear cover  66 , respectively. The bearing  69   a  and the bearing  69   b  that support the motor shaft  68 B are supported by the motor housing  64  and the gear case  65 . Thus, each component of the transmission mechanism unit  60  can be positioned with high accuracy without an increase in the number of components. 
     In the transmission mechanism unit  60 , a V-belt and a V-pulley are used in the first-stage transmission mechanism, and a timing belt and a timing pulley are used in the second-stage transmission mechanism. Thus, the timing belt can reliably transmit a high torque held at the time of deceleration to the spindle  606 , and efficiency in transmitting rotation improves. In addition, even in a case where an unexpected heavy load is produced in the cutting blade  61 , transmission of the load to the motor can be suppressed as the V-belt slides on the V-pulley, and any damage to the components is suppressed. Accordingly, durability of the miter saw  1  improves. In addition, no gear meshing is present in the transmission path. Thus, the miter saw  1  with ensured quietness can be achieved. 
     Furthermore, in the gear cover  66 , the guide  661 C and the guide  662 B are provided adjacent to the support part  661 B and the support part  662 A that support the bearing  70   b  and the bearing  71   b . Thus, even in a case where the countershaft  602  and the spindle  606  tilt due to the tension of the second belt  608  during assembly, this tilted state can be corrected with ease. Accordingly, assembly with high positioning accuracy can be achieved without an increase in the stepped portions and in the number of components, and assembleability and mass productivity can be improved. When the gear cover  66  is removed, the tension of the second belt  608  decreases automatically. Thus, replacement of the second belt  608  is facilitated, and maintenance to the belt can be improved. 
     Next, a second embodiment of the present invention will be described with reference to  FIGS. 10 to 13 . The present embodiment differs from the first embodiment in that a tapered guide is provided in a gear case. Members and configurations that are identical to those of the first embodiment will be given identical reference characters, and descriptions thereof will be omitted. Only the configurations that differ from those of the first embodiment will be described. 
       FIG. 10  illustrates an inside of a cutting unit  106  of a miter saw  101  according to the second embodiment.  FIG. 10  is a sectional view taken along the A-A plane indicated in  FIG. 1 .  FIGS. 11, 12, and 13  each illustrate an inside of the cutting unit  106  of the miter saw  101  according to the second embodiment.  FIGS. 11 to 13  are illustrations for describing an assembly process. 
     A gear case  165  covers a left side surface of the cutting unit  106  inside a gear housing  650  ( FIG. 3 ). The gear case  165  supports the bearing  69   b , the bearing  70   a , and the bearing  71   a . The gear case  165  is an example of the first support member in the present invention. 
     As illustrated in  FIG. 10 , a protrusion  651 , a protrusion  1652 , and a protrusion  1653  are provided on the gear case  165 . 
     The protrusion  1653  has a cylindrical shape extending in the rightward/leftward direction. The protrusion  1653  includes a support part  1653 A and a guide  1653 B. The support part  1653 A defines an inner peripheral surface of the protrusion  1653 . A right end portion of the support part  1653 A is open. A left end portion of the support part  1653 A is covered by a left side surface of a gear case  65 B. As illustrated in  FIG. 10 , the bearing  71   a  is disposed inside the support  1653 A. An inner diameter of the support part  1653 A is substantially equal to an outer diameter of the bearing  71   a . The bearing  71   a  is fitted inside the support part  1653 A and fixed therein. 
     The guide  1653 B is connected adjacent to a right side of the support  1653 A. The guide  1653 B has a tapered inner peripheral surface extending in the rightward/leftward direction. Right and left ends of the guide  1653 B are open. The guide  1653 B is inclined inward in a radial direction of the spindle  606  along a direction toward the support part  1653 A and the bearing  71   a , that is, along a direction toward the left side, and a diameter of the guide  1653 B thus decreases. An inner diameter of the guide  1653 B at its right end portion is greater than the outer diameter of the bearing  71   a . The support part  1652 A is an example of the first support part in the present invention. The guide  1652 B is an example of the first guide part in the present invention. 
     The protrusion  1653  has a cylindrical shape extending in the rightward/leftward direction. The protrusion  1653  includes a support part  1653 A and a guide  1653 B. The support part  1653 A defines an inner peripheral surface of the protrusion  1653 . A right end portion of the support part  1653 A is open. A left end portion of the support part  1653 A is covered by a left side surface of a gear case  165 . As illustrated in  FIG. 10 , the bearing  71   a  is disposed inside the support  1653 A. An inner diameter of the support part  1653 A is substantially equal to an outer diameter of the bearing  71   a . The bearing  71   a  is fitted inside the support part  1653 A and fixed therein. 
     The guide  1653 B is connected adjacent to a right side of the support  1653 A. The guide  1653 B has a tapered inner peripheral surface extending in the rightward/leftward direction. Right and left ends of the guide  1653 B are open. The guide  1653 B is inclined inward in a radial direction of the spindle  606  along a direction toward the support part  1653 A and the bearing  71   a , that is, along a direction toward the left side, and a diameter of the guide  1653 B thus decreases. An inner diameter of the guide  1653 B at its right end portion is greater than the outer diameter of the bearing  71   a . The support part  1653 A is an example of the second support part in the present invention. The guide  1653 B is an example of the second guide part in the present invention. 
     As illustrated in  FIG. 10 , a gear cover  166  is disposed on the right side of the gear case  165 . The gear cover  166  supports the bearing  70   b  and the bearing  71   b . The gear cover  166  is an example of the second support member in the present invention. 
     As illustrated in  FIG. 10 , a groove  1661  is formed inside the gear cover  166 . The groove  1661  includes a lid  661 A and a support part  661 B that are arrayed side by side in the rightward/leftward direction. 
     As illustrated in  FIG. 10 , the gear cover  166  is provided with a protrusion  1662 . The protrusion  1662  projects outward (rightward). The protrusion  1662  has a cylindrical shape extending in the rightward/leftward direction. The protrusion  1662  includes the support  662 A. 
     Next, a process of assembling the cutting unit  106  of the miter saw  101  according to the second embodiment will be described briefly. In the present embodiment, the countershaft  602  and the spindle  606  are attached to the gear cover  166  via the bearing  70   b  and the bearing  71   b . Then, the gear case  165  is attached. 
     When the second belt  608  is looped under tension over the third pulley  605  and the fourth pulley  607  after the countershaft  602  and the spindle  606  are attached to the gear cover  166 , due to the tension of the second belt  608 , an unfixed left end portion of the countershaft  602  tilts in a direction approaching the spindle  606 , and an unfixed left end portion of the spindle  606  tilts in a direction approaching the countershaft  602  ( FIG. 11 ). 
     In this tilted state, as illustrated in  FIG. 12 , the gear case  165  is attached from the left side (the gear cover  166  is attached to the gear case  165  from the right side). At this point, the bearing  70   a  attached to the countershaft  602  abuts the inner peripheral surface of the guide  1652 B. Thus, the bearing  70   a  and the countershaft  602  are guided in a direction away from the spindle  606 , and the tilted state of the countershaft  602  is corrected. In a similar manner, the bearing  71   a  attached to the spindle  606  abuts the inner peripheral surface of the guide  1653 B. Thus, the bearing  71   a  and the spindle  606  are guided in a direction away from the countershaft  602 , and the tilted state of the spindle  606  is corrected. 
     Then, as illustrated in  FIG. 13 , the bearing  70   a  is fixed inside the support  1652 A, and the bearing  71   a  is fixed inside the support  1653 A. 
     Thereafter, the first pulley  601  and the second pulley  603  are attached from the left side of the gear case  165 , and the first belt  604  is looped under tension over the first pulley  601  and the second pulley  603 . In addition, the cutting blade  61  is mounted to the mounting portion  606 A of the spindle  606 . 
     As described above, in the miter saw  101  according to the present embodiment, in the gear case  165 , the guide  1652 B and the guide  1653 B are provided adjacent to the support part  1652 A and the support part  1653 A that support the bearing  70   a  and the bearing  71   a . Thus, even in a case where the countershaft  602  and the spindle  606  tilt due to the tension of the second belt  608  during assembly, this tilted state can be corrected with ease. Accordingly, assembly with high positioning accuracy can be achieved without an increase in the stepped portions and in the number of components, and assembleability and mass productivity can be improved. 
     Next, a third embodiment of the present invention will be described with reference to  FIG. 14 . The present embodiment differs from the first embodiment in that the number of bearing members for a countershaft is increased. Incidentally, like parts and components are designated by the same reference numerals as those shown in the first embodiment to avoid duplicating description, and a structure different from the first embodiment will be described. 
       FIG. 14  illustrates an inside of a cutting unit  107  of a miter saw  102  according to the third embodiment.  FIG. 14  is a sectional view taken along the A-A plane indicated in  FIG. 1 . In the third embodiment, the fastener  609  that fixes the second pulley  603  in the first embodiment is removed, and another bearing  70   c  is added to the portion where the fastener  609  is located in the first embodiment. In order to dispose the bearing  70   c , a screw hole  9   b  is provided in a gear case  65 , and a bearing holding member  9  configured to hold the bearing  70   c  is fixed to the gear case  65  with a screw  9   a . The screw  9   a  penetrates the bearing holding member  9  and is screwed into the screw hole  9   b.    
     In the miter saw  102 , a countershaft  3602  is supported by the bearing  70   a , the bearing  70   b , and the bearing  70   c . Thus, tilting of the countershaft  3602  caused by a pulling force (tension) of a belt can be suppressed. In particular, the added bearing  70   c  is located closer to one end (left side) of the countershaft  3602  than the second pulley  603 . Thus, the countershaft  3602  is supported at both ends, and tilting of the countershaft can be further suppressed than in the first embodiment. 
     Next, a fourth embodiment of the present invention will be described with reference to  FIGS. 15 to 19 . The present embodiment differs from the first and second embodiments in that a gear cover is constituted by two separate members. Incidentally, like parts and components are designated by the same reference numerals as those shown in the first and second embodiments to avoid duplicating description, and a structure different from the first and second embodiments will be described. 
       FIG. 15  illustrates an inside of a cutting unit  206  of a miter saw  201  according to the fourth embodiment.  FIG. 15  is a sectional view taken along the A-A plane indicated in  FIG. 1 .  FIG. 16  is an exploded perspective view illustrating a configuration of a portion of the cutting unit  206  of the miter saw  201  according to the fourth embodiment. As illustrated in  FIG. 15 , the cutting unit  206  includes the motor  68 , a transmission mechanism unit  260 , and the cutting blade  61 . 
     Similar to the transmission mechanism  60  according to the first and second embodiments, the transmission mechanism unit  260  is configured to transmit rotation of the motor  68  to the cutting blade  61  in a two-stage belt system. As illustrated in  FIG. 15 , the transmission mechanism unit  260  includes the first pulley  601 , the countershaft  602 , a second pulley  2603 , the first belt  604 , the third pulley  605 , the fourth pulley  607 , and the second belt  608 . 
     The second pulley  2603  is a V-pulley. The second pulley  2603  has a function similar to that of the second pulley  603  of the first and second embodiments. As illustrated in  FIGS. 15 and 16 , the second pulley  2603  has a cylindrical shape extending in the rightward/leftward direction. A groove extending in a circumferential direction is formed in an outer peripheral surface of the second pulley  2603 . The second pulley  2603  has an outer diameter greater than an outer diameter of the first pulley  601 . The second pulley  2603  is fitted on an outer surface of a left end portion of the countershaft  602  projecting out of a gear case  265  via a washer  272  and fixed with a fastener  609  at the outside (left side) of the gear case  265 . The second pulley  2603  is configured to corotate with the countershaft  602 . The second pulley  2603  is an example of the second pulley in the present invention. 
     Next, the shape of the gear case  265  in the miter saw  201  according to the fourth embodiment will be described with reference to  FIG. 16 . The gear case  265  of the fourth embodiment differs from the gear case  65  of the first embodiment in a structure in which a pair of protrusions  655  and  656  is provided around a groove  654 . 
     The gear case  265  supports the bearing  69   b , the bearing  70   a , and the bearing  71   a . As illustrated in  FIG. 16 , the gear case  265  is formed integrally by the gear case  65 A and a gear case  265 B. The gear case  265  is an example of the first support member in the present invention. 
     The gear case  265 B has substantially elliptical right and left side surfaces. The groove  654  having a substantially elliptical cross-section is formed at a center portion of the right side surface of the gear case  265 B. The protrusion  655  and the protrusion  656  are provided at positions outside of intersections each between a major axis of the groove  654  and elliptical arcs of the groove  654 . 
     The protrusion  655  has an elliptical arc shape. The protrusion  655  is provided in the vicinity of the support  652 A that supports the bearing  70   a . The protrusion  655  projects rightward from the right side surface of the gear case  265 B. The protrusion  656  has an elliptical arc shape substantially identical to the protrusion  655 . The protrusion  656  is provided in the vicinity of the support  653 A that supports the bearing  71   a . The protrusion  656  projects rightward from the right side surface of the gear case  265 B. The protrusion  655  and the protrusion  656  have substantially equal lengths in their projecting direction, that is, in the rightward/leftward direction. The protrusion  655  and the protrusion  656  are an example of a first positioning portion in the present invention. 
     Next, a shape of a gear cover  266  of the miter saw  201  according to the fourth embodiment will be described in detail with reference to  FIGS. 15, 16, and 17 .  FIG. 17  is an exploded perspective view illustrating the shape of the gear cover  266  of the miter saw  201  according to the fourth embodiment. 
     As illustrated in  FIG. 16 , the gear cover  266  is disposed on the right side of the gear case  265 . The gear cover  266  supports the bearing  70   b  and the bearing  71   b . The gear cover  266  is an example of the second support member in the present invention. The gear case  265  and the gear cover  266  are an example of the support base. 
     In the fourth embodiment, as illustrated in  FIGS. 16 and 17 , the gear cover  266  includes a bearing holder  2661  and a bearing holder  2663 . The bearing holder  2661  supports the bearing  71   b . The bearing holder  2661  is an example of a first support portion in the present invention. The bearing holder  2663  supports the bearing  70   b , and is an example of a second support portion in the present invention. 
     As illustrated in  FIGS. 16 and 17 , the bearing holder  2661  has a cylindrical shape having a substantially elliptical cross-section and extending in the rightward/leftward direction. The bearing holder  2661  is so disposed as to cover the groove  654  in the gear case  265 . The bearing holder  2661  is formed integrally by a bearing holder  2661 A and a bearing holder  2661 B. 
     The bearing holder  2661 B supports the bearing  71   b . A protrusion  2662  is provided on a right side surface of the bearing holder  2661 B. The protrusion  2662  projects outward (rightward). The protrusion  2662  has a cylindrical shape extending in the rightward/leftward direction. The protrusion  2662  includes a support part  662 A and an insertion portion  2662 B. 
     The support part  662 A has a cylindrical inner peripheral surface extending in the rightward/leftward direction. A left end portion of the support part  662 A is open. A right end portion of the support part  662 A has a circular ring shape having an opening  662   a  formed at its center portion. The support part  662 A is formed such that the opening  662   a  has an inner diameter greater than an outer diameter of the spindle  606 . An inner diameter of the inner peripheral surface of the support part  662 A is substantially equal to an outer diameter of the bearing  71   b . As illustrated in  FIG. 15 , the bearing  71   b  is fitted and fixed inside the support  662 A. The support part  662 A is an example of the second support part in the present invention. 
     The insertion portion  2662 B is connected adjacent to a left side of the support  662 A. The insertion portion  2662 B has a cylindrical inner peripheral surface extending in the rightward/leftward direction. Right and left ends of the insertion portion  2662 B are open. An inner diameter of the inner peripheral surface of the insertion portion  2662 B is greater than the inner diameter of the inner peripheral surface of the support part  662 A and the outer diameter of the bearing  71   b . The spindle  606  penetrates through the insertion portion  2662 B. The inner diameter of the inner peripheral surface of the insertion portion  2662 B may be substantially equal to the inner diameter of the inner peripheral surface of the support part  662 A and the outer diameter of the bearing  71   b.    
     As illustrated in  FIG. 17 , a stepped portion  2661   b  is formed in an outer peripheral surface of the bearing holder  2661 B. The stepped portion  2661   b  is formed by cutting out a left end portion of the outer peripheral surface of the bearing holder  2661 B in an elliptical arc shape. The shape of a cutout is substantially identical to the shape of the protrusion  656  on the gear case  265 B. Specifically, the stepped portion  2661   b  has a shape engageable with the protrusion  656 . 
     As illustrated in  FIG. 15 , the bearing holder  2661 A extends from the bearing holder  2661 B so as to cover the countershaft  602 . A through-hole  2661   d  is formed in the bearing holder  2661 A, and the through-hole  2661   d  opposes a right end portion of the countershaft  602 . The through-hole  2661   d  is a substantially cylindrical hole penetrating the bearing holder  2661 A in the rightward/leftward direction. The through-hole  2661   d  has an inner diameter greater than an outer diameter of the bearing  70   b . The through-hole  2661   d  is an example of a through-hole in the present invention. 
     A pair of cylindrical portions  2661 C is provided on an outer peripheral surface of the bearing holder  2661 A. Fasteners, such as screws, are to be inserted into the cylindrical portions  2661 C. As illustrated in  FIG. 16 , the cylindrical portions  2661 C each have a substantially cylindrical shape extending in the rightward/leftward direction. The cylindrical portions  2661 C are disposed at positions symmetric about the countershaft  602 . In the present embodiment, the cylindrical portions  2661 C are provided at a position farthest from the motor shaft  68 B and a position closest to the motor shaft  68 B on the outer peripheral surface of the bearing holder  2661 A. 
     As illustrated in  FIG. 17 , a stepped portion  2661   a  is formed in the outer peripheral surface of the bearing holder  2661 A. The stepped portion  2661   a  is formed by cutting out a left end portion of the outer peripheral surface of the bearing holder  2661 A in an elliptical arc shape. The shape of this cutout is substantially identical to the shape of the protrusion  655  on the gear case  265 B. Specifically, the stepped portion  2661   a  has a shape engageable with the protrusion  655 . 
     The stepped portion  2661   a  formed in the bearing holder  2661 A and the stepped portion  2661   b  formed in the bearing holder  2661 B constitute a pair, and this pair forms a complementary structure with the pair of the protrusion  655  and the protrusion  656  provided on the gear case  265 B. As the stepped portion  2661   a  and the stepped portion  2661   b  engage with the protrusion  655  and the protrusion  656 , respectively, the bearing holder  2661  is positioned relative to the gear case  265 , and the movement of the bearing holder  2661  in radial directions of the countershaft  602  and the spindle  606  is restricted. The stepped portion  2661   a  and the stepped portion  2661   b  are an example of the first positioning portion in the present invention. 
     A stepped portion  2661   c  is provided in the bearing holder  2661 A at an open end in a right side end portion of the through-hole  2661   d . The stepped portion  2661   c  is formed by cutting out a right side surface of the bearing holder  2661 A in a circular ring shape along an outer periphery of the open end of the through-hole  2661   d . An inner diameter of the stepped portion  2661   c  coincides with an inner diameter of the through-hole  2661   d . A diameter of the stepped portion  2661   c  at a radially outward side will be referred to as a diameter of the open end of the through-hole  2661   d . The stepped portion  2661   c  is an example of a second positioning portion in the present invention 
     As illustrated in  FIG. 15 , the bearing holder  2663  is so disposed as to cover the open end of the through-hole  2661   d  on the right side of the bearing holder  2661 . As illustrated in  FIG. 16 , the bearing holder  2663  includes a pair of projections  2663 C provided on an outer peripheral portion. The bearing holder  2663  has a substantially disc shape having an outer diameter greater than the diameter of the open end of the through-hole  2661   d.    
     The pair of projections  2663 C each project outward from the outer peripheral portion of the bearing holder  2663  in the radial direction of the countershaft  602 . The projections  2663 C are provided at positions corresponding to the respective cylindrical portions  2661 C provided on the bearing holder  2661 . A through-hole is formed at a center portion of each projection  2663 C. A fastener, such as a screw, is to be inserted into this through-hole. 
     A protrusion  2664  is provided at a center portion of the bearing holder  2663 . The protrusion  2664  has a cylindrical shape extending in the rightward/leftward direction. A right end portion of the protrusion  2664  projects further rightward than the projections  2663 C of the bearing holder  2663 . A left end of the protrusion  2664  is connected to a left side surface  2663 B of the bearing holder  2663 . An inside of the protrusion  2664  has a two-step form. A lid  2664 A and a connecting portion  2664 B are disposed side by side in the rightward/leftward direction. 
     The lid  2664 A has a cylindrical inner peripheral surface extending in the rightward/leftward direction. A left end portion of the lid  2664 A is open. A right end portion of the lid  2664 A is covered by a right side surface  2663 A of the bearing holder  2663 . The inner peripheral surface of the lid  2664 A has an inner diameter smaller than the outer diameter of the bearing  70   b  and greater than the outer diameter of the countershaft  602  and an inner diameter of the bearing  70   b.    
     The connecting portion  2664 B is connected adjacent to a left side of the lid  2664 A. The connecting portion  2664 B has a tapered inner peripheral surface extending in the rightward/leftward direction. Right and left ends of the connecting portion  2664 B are open. The connecting portion  2664 B is inclined inward in the radial direction of the countershaft  602  along a direction toward the lid  2664 A, that is, along a direction toward the right side, and a diameter of the connecting portion  2664 B thus decreases. An inner diameter of the inner peripheral surface of the connecting portion  2664 B is equal to the inner diameter of the lid  2664 A at the right end portion of the connecting portion  2664 B. The left end of the connecting portion  2664 B connects to the left side surface  2663 B of the bearing holder  2663 . 
     A protrusion  2665  is provided on the left side surface  2663 B of the bearing holder  2663 . The protrusion  2665  has a cylindrical shape extending in the rightward/leftward direction. The protrusion  2665  includes a support part  2665 A. The protrusion  2665  has an outer diameter substantially equal to the diameter of the open end of the through-hole  2661   d . The length of a portion of the outer peripheral surface of the protrusion  2665  projecting from the left side surface  2663 B, that is, the length of that portion in the rightward/leftward direction is substantially equal to the length, in the rightward/leftward direction, of the portion cut out from the bearing holder  2661 A. Specifically, the protrusion  2665  has a shape engageable with the stepped portion  2661   c . The protrusion  2665  forms a spigot structure with the stepped portion  2661   c . As the protrusion  2665  and the stepped portion  2661   c  engage with each other, the movement of the bearing holder  2663  in the radial direction of the countershaft  602  is restricted. The protrusion  2665  is an example of a second engagement portion in the present invention. 
     The support part  2665 A has a cylindrical inner peripheral surface extending in the rightward/leftward direction. A left end portion of the support part  2665 A is open. A right end portion of the support part  2665 A connects to the left side surface  2663 B of the bearing holder  2663 . The support part  2665 A is located on the left side of the connecting portion  2664 B. An inner diameter of the inner peripheral surface of the support part  2665 A is greater than an inner diameter of the inner peripheral surface of the lid  2664 A and an inner diameter of the inner peripheral surface of the connecting portion  2664 B and substantially equal to the outer diameter of the bearing  70   b . A length of the support part  2665 A in the rightward/leftward direction is smaller than a length of the bearing  70   b  in the rightward/leftward direction (axial direction). The length of the support part  2665 A in the rightward/leftward direction may be substantially equal to the length of the bearing  70   b  in the rightward/leftward direction (axial direction) or may be greater than the length of the bearing  70   b  in the rightward/leftward direction (axial direction). As illustrated in  FIG. 15 , the bearing  70   b  is disposed inside the support part  2665 A. The support part  2665 A is an example of the first support part in the present invention. 
     Next, a process of assembling the cutting unit  206  of the miter saw  201  according to the fourth embodiment will be described with reference to  FIGS. 15, 18, and 19 .  FIGS. 18 and 19  each illustrate an inside of the cutting unit  206  of the miter saw  201  according to the fourth embodiment.  FIGS. 18 and 19  are illustrations for describing an assembly process. In the present embodiment, the motor shaft  68 B, the countershaft  602 , and the spindle  606  are attached to the gear case  265  via the bearing  69   b , the bearing  70   a , and the bearing  71   a . Then, the gear cover  266  is attached to the gear case  265 . A method of attaching the motor shaft  68 B, the countershaft  602 , and the spindle  606  to the gear case  265  is similar to that of the first embodiment, and thus detailed descriptions thereof will be omitted. 
     The bearing  69   b , the bearing  70   a , and the bearing  71   a  are fixed to the gear case  265 , and the left sides of the motor shaft  68 B, the countershaft  602 , and the spindle  606  are positioned relative to the gear case  265 . The first pulley  601 , the second pulley  2603 , and the first belt  604  are attached to predetermined positions. The first pulley  601 , the second pulley  2603 , and the first belt  604  may be attached after the gear cover  266  is attached. 
     Next, as illustrated in  FIG. 18 , the second belt  608  is looped under tension over the third pulley  605  and the fourth pulley  607 . At this point, due to the tension of the second belt  608 , the unfixed right end portion of the countershaft  602  tilts in a direction approaching the spindle  606 , and the unfixed right end portion of the spindle  606 , that is, the side where the mounting portion  606 A is provided tilts in a direction approaching the countershaft  602 . 
       FIG. 18  illustrates an axis X 1  of the countershaft  602  and an axis X 2  of the spindle  606 . After the second belt  608  is looped under tension, the axis X 1  and the axis X 2  tilt so as to approach each other along the rightward direction. A distance between the two axes X 1  and X 2  does not vary at the positions of the bearing  70   a  and the bearing  71   a  before and after the second belt  608  is looped under tension. However, the distance between the two axes X 1  and X 2  is reduced at the positions of the third pulley  605  and the fourth pulley  607  upon the second belt  608  being looped under tension. The distance between the two axes X 1  and X 2  is further reduced at the positions of the bearing  70   b , the bearing  71   b , and the mounting portion  606 A provided further rightward. 
     In this tilted state, the gear cover  266  is attached to the gear case  265  from the right side. In the present embodiment, the bearing holder  2661  is attached to the gear case  265 , first. Then, the bearing holder  2663  is attached to the bearing holder  2661 . 
     Prior to attaching the bearing holder  2661  to the gear case  265 , as illustrated in  FIG. 18 , the bearing  70   b  and the bearing  71   b  are attached to the countershaft  602  and the spindle  606 , respectively. The bearing holder  2661  and the bearing holder  2663  may be attached to each other after the bearing  70   b  and the bearing  71   b  are attached to the bearing holder  2663  and the bearing holder  2661  from the left side, respectively. Prior to attaching the countershaft  602  and the spindle  606  to the gear case  265 , the bearing  70   b  and the bearing  71   b  may be attached to the countershaft  602  and the spindle  606 , respectively. 
     The second belt  608  is looped under tension, and the bearing holder  2661  is brought closer to the countershaft  602  with a tilted axis X 1  and the spindle  606  with a tilted axis X 2  from the right side (the gear cover  266  is brought closer from the left side). At this point, the spindle  606  extending further to the right side than the countershaft  602  enters the bearing holder  2661  before the countershaft  602  does. 
     The right end portion of the spindle  606 , that is, the mounting portion  606 A passes through the insertion portion  2662 B and enters the support  662 A. The inner diameter of the insertion portion  2662 B is greater than the outer diameters of the spindle  606  and the bearing  71   b , and the inner diameter of the support part  662 A is greater than the outer diameter of the spindle  606 . Therefore, the mounting portion  606 A can easily enter the support part  662 A with the spindle  606  remaining in a tilted state. 
     The inner diameter of the support part  662 A and the outer diameter of the bearing  71   b  are substantially equal to each other. Thus, upon the portion of the spindle  606  where the bearing  71   b  is attached reaching the inside of the support  662 A, an outer peripheral surface of the bearing  71   b  abuts the inner peripheral surface of the support  662 A. In this abutting state, the spindle  606  with the bearing  71   b  attached thereto is pressed and fitted into the support  662 A. Thus, the tilted state of the spindle  606  is corrected, and the bearing  71   b  is fitted and fixed in the support  662 A. 
     At this point, the right end portion of the countershaft  602  where the bearing  70   b  is attached also enters the bearing holder  2661  and reaches the inside of the through-hole  2661   d . However, the inner diameter of the through-hole  2661   d  is greater than the outer diameters of the countershaft  602  and the bearing  70   b . Thus, the right end portion of the countershaft  602  can easily pass through the through-hole  2661   d  in a tilted state. 
     The bearing  71   b  is fixed inside the support  662 A, and the bearing holder  2661  abuts the right side surface of the gear case  265 . Then, as illustrated in  FIG. 19 , the protrusion  655  and the protrusion  656  on the gear case  265  are made to engage with, respectively, the stepped portion  2661   a  and the stepped portion  2661   b  of the bearing holder  2661 . Thus, the bearing holder  2661  is positioned relative to the gear case  265 , and the tilted state of the spindle  606  is further corrected. In this state, the bearing holder  2661  is fixed to the gear case  265  with a fastener, such as a screw. 
     At this point, as illustrated in  FIG. 19 , the mounting portion  606 A of the spindle  606  projects rightward through the opening  662   a  in the protrusion  2662 , and the countershaft  602  with the bearing  70   b  mounted thereon projects rightward out of the open end of the through-hole  2661   d . Although the tilted state of the axis X 1  of the countershaft  602  is retained, the tilted state of the axis X 2  of the spindle  606  is corrected. Therefore, at the positions of the third pulley  605  and the fourth pulley  607 , the distance between the two axes X 1  and X 2  becomes closer or substantially equal to the distance held before the second belt  608  is looped under tension. Meanwhile, at the positions of the bearing  70   b , the bearing  71   b , and the mounting portion  606 A, the distance between the two axes X 1  and X 2  becomes greater than the distance held before the bearing holder  2661  is attached. However, since the axis X 1  of the countershaft  602  is tilted, the distance is smaller than the distance held before the second belt  608  is looped under tension. 
     Next, the bearing holder  2663  is attached to the bearing holder  2661 . The bearing holder  2663  is brought closer to the right end portion of the countershaft  602  with a tilted axis X 1  from the right side. The outer diameter of the countershaft  602  is smaller than the inner diameters of the support part  2665 A, the connecting portion  2664 B, and the lid  2664 A. Therefore, the right end portion of the countershaft  602  passes through the support part  2665 A with the countershaft  602  remaining in a tilted state and can easily enter the connecting portion  2664 B and the lid  2664 A. 
     The inner diameter of the support part  2665 A and the outer diameter of the bearing  70   b  are substantially equal to each other. Thus, upon the portion of the countershaft  602  where the bearing  70   b  is attached reaching the inside of the support part  2665 A, the outer peripheral surface of the bearing  70   b  abuts the inner peripheral surface of the support part  2665 A. In this abutting state, the countershaft  602  with the bearing  70   b  attached thereto is pressed and fitted into the support part  2665 A. Thus, the bearing  70   b  is fitted and fixed in the support part  2665 A. At this point, the right end portion of the countershaft  602  is disposed inside the lid  2664 A. 
     The bearing  70   b  is fixed inside the support part  2665 A, and the bearing holder  2663  abuts the bearing holder  2661 . Then, as illustrated in  FIG. 15 , the protrusion  2665  on the bearing holder  2663  is made to engage with the stepped portion  2661   c  of the bearing holder  2661 . Thus, the bearing holder  2663  is positioned relative to the bearing holder  2661 , and the tilted state of the countershaft  602  is corrected. In this state, the bearing holder  2663  is fixed to the bearing holder  2661  with a fastener, such as a screw. 
     As described above, as the bearing holder  2663  is fixed to the bearing holder  2661 , the tilted state of the axis X 1  of the countershaft  602  is corrected, and the distance between the two axes X 1  and X 2  becomes substantially equal to the distance held before the second belt  608  is looped under tension throughout the countershaft  602  and the spindle  606 . In other words, each member can be positioned with high accuracy. 
     Thereafter, the cutting blade  61  is mounted to the mounting portion  606 A of the spindle  606  via a fastener  2611 . 
     As described thus far, in the miter saw  201  according to the present embodiment, the gear cover  266  is divided into the bearing holder  2661  and the bearing holder  2663 , the bearing  70   b  only is supported by the bearing holder  2661 , and the bearing  70   a  only is supported by the bearing holder  2663 . Therefore, the bearings  70   b  and  70   a  can be easily inserted and fitted in the bearing holders  2661  and  2663 . In addition, even in a case where the countershaft  602  and the spindle  606  tilt due to the tension of the second belt  608  during assembly, the tilted state of each of the countershaft  602  and the spindle  606  can be corrected separately. Accordingly, assembleability can be further improved. 
     By making the pair of protrusions  655  and  656  provided on the gear case  265  engage with the pair of steps  2661   a  and  2661   b  formed in the bearing holder  2661 , tilting of the spindle  606  can be easily and reliably corrected. By making the protrusion  2665  provided on the bearing holder  2663  engage with the stepped portion  2661   c  formed in the bearing holder  2661 , tilting of the countershaft  602  can be easily and reliably corrected. Therefore, the distance between the axes X 1  and X 2  of the countershaft  602  and the spindle  606  can be reliably corrected, and assembly with high positioning accuracy can be achieved. Accordingly, assembleability and mass productivity can be improved. 
     Next, a fifth embodiment of the present invention will be described with reference to  FIGS. 20 and 21 . The present embodiment differs from the first to fourth embodiments in a configuration in which an air hole is provided in a gear cover. Incidentally, like parts and components are designated by the same reference numerals as those of the foregoing embodiments to avoid duplicating description, and a structure different from the foregoing embodiments will only be described. 
       FIG. 20  is an exploded perspective view illustrating a configuration of a portion of a cutting unit  306  of a miter saw  301  according to the fifth embodiment.  FIG. 21  is an illustration for describing a flow of a cooling air W in the miter saw  301  according to the fifth embodiment.  FIG. 21  is a sectional view taken along the A-A plane indicated in  FIG. 1 . 
     As illustrated in  FIG. 20 , a gear cover  366  is disposed on the right side of a gear case  265 . The gear cover  366  supports the bearing  70   b  and the bearing  71   b . The gear cover  366  is an example of the second support member in the present invention. Further, the gear case  265  and the gear cover  366  are an example of the support base in the present invention. 
     The gear cover  366  includes a bearing holder  3661  and a bearing holder  3663 . The bearing holder  3661  supports the bearing  71   b , and is an example of a first support portion in the present invention. The bearing holder  3663  supports the bearing  70   b , and is an example of a second support portion in the present invention. 
     The bearing holder  3661  is formed integrally by a bearing holder  3661 A and a bearing holder  2661 B. The bearing holder  3661  is so disposed as to cover a groove  654  in the gear case  265 . 
     As illustrated in  FIG. 21 , the bearing holder  3661 A extends from the bearing holder  2661 B so as to cover the countershaft  602 . A through-hole  3661   d  is formed in the bearing holder  3661 A, and the through-hole  3661   d  opposes a right end portion of the countershaft  602 . The through-hole  3661   d  has an inner diameter greater than an outer diameter of the bearing  70   b . The through-hole  3661   d  is an example of the through-hole in the present invention. 
     As illustrated in  FIG. 20 , a notch  3661   e  is formed in an outer peripheral surface of the bearing holder  3661 A. The notch  3661   e  has a rectangular shape extending leftward from an open end on a right side end portion of the through-hole  3661   d . The notch  3661   e  is formed at an outer surface of the bearing holder  3661 A at a position adjacent to one of the cylindrical portions  2661 C which is closer to the motor shaft  68 B than the other cylindrical portion  2661 C is to the motor shaft  68 B. The notch  3661 E is also adjacent to the cylindrical portion  2661 C. The notch  3661   e  is an example of a notch in the present invention. 
     A stepped portion  3661   c  is formed in the bearing holder  3661 A at the open end of the through-hole  3661   d . The stepped portion  3661   c  is formed by cutting out a right side surface of the bearing holder  3661 A in a circular arc shape along an outer periphery of the open end of the through-hole  3661   d . The through-hole  3661   d  and the stepped portion  3661   c  are identical in shape to the through-hole  2661   d  and the stepped portion  2661   c  of the fourth embodiment except that the through-hole  3661   d  and the stepped portion  3661   c  are partially cut out to form the notch  3661   e.    
     As illustrated in  FIG. 21 , the bearing holder  3663  is so disposed as to cover the open end of the through-hole  3661   d  on the right side of the bearing holder  3661 . As illustrated in  FIG. 20 , the bearing holder  3663  includes a main body  3663 A, a projection  2663 C, and a projection  3663 D. 
     The main body  3663 A has a substantially circular disc shape having an outer diameter greater than a diameter of the open end of the through-hole  3661   d . The main body  3663 A covers a right side end portion of a protrusion  2664  provided at a center portion of the bearing holder  3663 . 
     The projection  2663 C is provided at a position corresponding to the one cylindrical portion  2661 C of the two cylindrical portions  2661 C on the bearing holder  3661  that is farther from the motor shaft  68 B. A through-hole is formed in the projection  2663 C, and a fastener, such as a screw, is to be inserted into the through-hole. As illustrated in  FIG. 20 , the projection  2663 C projects outward in a radial direction of the countershaft  602 , that is, projects in a direction away from the motor shaft  68 B. 
     The projection  3663 D is provided at a position corresponding to the notch  3661   e  and the one cylindrical portion  2661 C of the two cylindrical portions  2661 C on the bearing holder  3661  that is closer to the motor shaft  68 B. The projection  3663 D projects from the main body  3663 A outward in the radial direction of the countershaft  602 , that is, projects in a direction approaching the motor shaft  68 B. The projection  3663 D covers a right end portion of the cylindrical portion  2661 C and an open end of the notch  3661   e . The projection  3663 D projects further outward in the radial direction of the countershaft  602  than the open end of the notch  3661   e . A through-hole is provided in the projection  3663 D at a position corresponding to the cylindrical portion  2661 C, and a fastener, such as a screw, is to be inserted into the through-hole. The protrusion  3663 D is an example of a closure portion in the present invention. 
     A process of assembling the cutting unit  306  of the miter saw  301  according to the fifth embodiment is similar to that of the fourth embodiment, and thus descriptions thereof will be omitted. 
     The bearing holder  3663  is attached to the bearing holder  3661 . Then, the open end of the notch  3661   e  is closed by a projection  3663 D, and an air hole is defined in the gear cover  366 . This air hole is disposed in the vicinity of a portion on the outer peripheral surface of the countershaft  602  where the bearing  70   b  is attached. The projection  3663 D further projects in a direction approaching the motor shaft  68 B at the right side of the air hole. 
       FIG. 21  illustrates a flow of a cooling air within a housing of the miter saw  301  by an arrow W. When the motor  68  starts running and the fan  68 C corotates with the motor shaft  68 B, the cooling air W is produced by an outside air sucked in through an intake port  64   a  of the motor housing  64 . After passing through a discharge port  65   a  provided in the gear case  65 A, the cooling air W travels in a direction from the first pulley  601  toward the second pulley  2603  within the gear housing  650  and enters the inside of the gear case  265  through a position where the second pulley  2603  is attached. Then, the cooling air W travels along the countershaft  602  inside the gear case  265  and the gear cover  366  and is discharged to the outside of the gear case  265  and the gear cover  366  through the air hole defined in the gear cover  366 . A flow of the discharged cooling air W in a direction toward the cutting blade  61  is shut off by a projecting portion of the projection  3663 D. 
     As described thus far, in the miter saw  301  according to the present embodiment, the air hole is defined in the gear cover  366 , and the cooling air W produced through rotation of the fan  68 C travels to the vicinity of the bearing  70   b  along the countershaft  602  within the gear case  265  and the gear cover  366 , and this cooling air W is discharged through the air hole. Therefore, even in a case where the temperature of the countershaft  602 , the bearing  70   b , and the spindle  606  rises to a high temperature due to the heat produced in the second belt  608  while the miter saw  301  is in use, such components can be cooled efficiently with the cooling air W. A portion of the air hole which is closer to the cutting blade  61  than a remaining of the air hole is to the cutting blade  61  is closed by the projection  3663 D of the gear cover  366 . Thus, entry of cutting dust into the gear cover  366  can be suppressed during cutting work with the cutting blade  61 . Accordingly, suspension of work due to a high temperature or entry of a foreign object can be suppressed, and improved operability and improved tool durability are provided. The projection  3663 D projects from the open end of the notch  3661   e  in a direction approaching the motor shaft  68 B. Thus, entry of cutting dust can be suppressed effectively. 
     Next, a sixth embodiment of the present invention will be described with reference to  FIGS. 22 and 23 . A miter saw according to the sixth embodiment differs from that of the first embodiment in that a lock mechanism described later is added to the cutting unit  6 . The two embodiments are in common in other respects. Hereinafter, a modified cutting unit  6  will be described. In the sixth embodiment, the guide in the first embodiment is omitted. 
     As illustrated in  FIG. 22 , the miter saw according to the sixth embodiment includes a gear housing  4650 , a motor housing  4064 , a saw cover (not illustrated), and a gear case  4065 . The motor housing  4064  houses a motor body  4068 A. 
     The gear housing  4650  houses therein a portion of a transmission mechanism unit  4060 . The gear case  4065  is fixed to the right side of the gear housing  4650 . The motor housing  4064  is fixed to the right side of the gear case  4065 . A through-hole  4041   j  is provided in a front portion of the gear housing  4650 , and the through-hole  4041   j  penetrates a left side surface of the gear housing  4650  in the rightward/leftward direction. 
     The motor housing  4064  has a shape extending rightward from an upper portion of the gear housing  4650 . The motor housing  4064  is disposed above a cutting blade  4061 . The motor body  4068 A is housed inside the motor housing  4064 . As illustrated in  FIG. 22 , the motor body  4068 A includes a motor shaft  4068 B. The motor shaft  4068 B projects leftward. A fan  4068 C and a first pulley  4601  are so mounted to the motor shaft  4068 B as to rotate coaxially and integrally. 
     The gear case  4065  is fixed to the gear housing  4650  with a screw. The gear case  4065  accommodates therein a bearing  4070   a  and a bearing  4071   a . The bearing  4070   a  includes a housing washer and a shaft washer, and a plurality of balls is provided between the housing washer and the shaft washer. A gear cover  4066  is attached to the right side of the gear case  4065 . The housing washer of the bearing  4070   a  is fixed to the gear case  4065 . The bearing  4071   a  is a slide metal piece and has a diameter smaller than that of the bearing  4070   a . Thus, the size of a portion that supports the bearing  4071   a  can be reduced. A through-hole  4041   k  is provided in a front portion of the gear case  4065 , and the through-hole  4041   k  penetrates the gear case  4065  in the rightward/leftward direction. 
     A portion of the transmission mechanism unit  4060  is housed and supported between the gear case  4065  and the gear cover  4066 . The gear cover  4066  is so mounted to a gear housing  4650  as to cover a portion of the transmission mechanism unit  4060 . The gear cover  4066  accommodates therein a bearing  4071   b . The bearing  4071   b  includes a housing washer and a shaft washer, and a plurality of balls is provided between the housing washer and the shaft washer. The housing washer of the bearing  4071   b  is fixed to the gear cover  4066 . The bearing  4071   b  has a diameter greater than that of the bearing  4071   a.    
     As illustrated in  FIG. 22 , the transmission mechanism unit  4060  includes the first pulley  4601 , a second pulley  4603 , a first belt  4604 , a countershaft  4602 , a third pulley  4605 , a fourth pulley  4607 , a second belt  4608 , and a spindle  4606 . The first belt  4604  is looped under tension over the first pulley  4601  and the second pulley  4603 . The countershaft  4602  is coaxially bonded to the second pulley  4603 . The third pulley  4605  has a diameter smaller than that of the second pulley  4603  and is coaxially mounted to the countershaft  4602 . The fourth pulley  4607  is disposed frontward of the third pulley  4605  with a space provided therebetween. The second belt  4608  is looped under tension over the third pulley  4605  and the fourth pulley  4607 . The spindle  4606  is coaxially bonded to the fourth pulley  4607 . The second belt  4608  is a timing belt. 
     The countershaft  4602 , the third pulley  4605 , the spindle  4606 , the fourth pulley  4607 , and the second belt  4608  are supported and housed between the gear case  4065  and the gear cover  4066 . 
     The first pulley  4601  is substantially circular as viewed in a side view in the rightward/leftward direction and has a substantially columnar shape with an axis extending in the rightward/leftward direction. The first pulley  4601  is so mounted as to be coaxial with the motor shaft  4068 B at a left end portion of the motor shaft  4068 B of the motor body  4068 A. A plurality of grooves is formed in an outer peripheral surface of the first pulley  4601 , and the plurality of grooves extends along a circumferential direction. The plurality of grooves is formed parallel to each other and arrayed in the rightward/leftward direction. 
     The second pulley  4603  is substantially circular as viewed in a side view in the rightward/leftward direction and has a substantially cylindrical shape with an axis extending in the rightward/leftward direction. Similarly to the first pulley  4601 , a plurality of grooves is formed in an outer peripheral surface of the second pulley  4603 , and the plurality of grooves extends along a circumferential direction. The plurality of grooves in the second pulley  4603  is disposed parallel to each other and arrayed in the rightward/leftward direction in the outer peripheral surface of the second pulley  4603 . The second pulley  4603  is mounted coaxially with the countershaft  4602 . 
     The first belt  4604  is looped under tension over the first pulley  4601  and the second pulley  4603  ( FIGS. 23A and 23B ). The first belt  4604  is a V-belt. A width of the first belt  4604  in the rightward/leftward direction is substantially equal to a width of the first pulley  4601  and a width of the second pulley  4603 . The first belt  4604  is an endless belt. A plurality of protrusions is formed on an inner peripheral surface of the first belt  4604 . The plurality of protrusions is arrayed in the widthwise direction of the first belt  4604  and extends in a circumferential direction of the belt. The plurality of protrusions engages with the plurality of grooves formed in the outer peripheral surface of each of the first pulley  4601  and the second pulley  4603 . As the first belt  4604  engages with and is looped under tension over the first pulley  4601  and the second pulley  4603 , the first belt  4604  can transmit rotation of the first pulley  4601  to the second pulley  4603 . The first pulley  4601  and the second pulley  4603  are each a V-pulley. 
     The countershaft  4602  is a substantially cylindrical member having an axis extending in the rightward/leftward direction. A left end portion of the countershaft  4602  is rotatably supported by the bearing  4070   a . A right end portion of the countershaft  4602  is rotatably supported by the gear cover  4066  via a bearing  4070   b . The third pulley  4605  is coaxially mounted to the right end portion of the countershaft  4602 . 
     The third pulley  4605  is a substantially cylindrical member extending in the rightward/leftward direction. The third pulley  4605  is a timing pulley. A plurality of gear teeth is formed in an outer peripheral surface of the third pulley  4605 . The plurality of gear teeth extends in the rightward/leftward direction and is arrayed at regular intervals in the circumferential direction. The third pulley  4605  has an inner peripheral surface, and this inner peripheral surface fits an outer peripheral surface of the countershaft  4602 . As the third pulley  4605  fits the countershaft  4602 , the third pulley  4605  can corotate with the countershaft  4602 . The third pulley  4605  is an example of a driving pulley. 
     The fourth pulley  4607  is disposed frontward of the third pulley  4605  with a space provided therebetween. The fourth pulley  4607  is so disposed as to be flush with the third pulley  4605  in the rightward/leftward direction. The fourth pulley  4607  is a substantially cylindrical member having an axis extending in the rightward/leftward direction. The fourth pulley  4607  is a timing pulley. A plurality of gear teeth is formed in an outer peripheral surface of the fourth pulley  4607 . The plurality of gear teeth extends in the rightward/leftward direction and is arrayed at regular intervals in a circumferential direction. The fourth pulley  4607  has an inner peripheral surface, and this inner peripheral surface fits the spindle  4606 . A plurality of engaging holes  4042   k  is disposed in a left side surface of the fourth pulley  4607 . The plurality of engaging holes  4042   k  is disposed at regular intervals in the circumferential direction. The engaging holes  4042   k  are each formed to have a substantially circular shape as viewed in a left side view. The engaging holes  4042   k  are so formed as to be recessed in the rightward direction from the left side surface of the fourth pulley  4607 . The fourth pulley  4607  is an example of a driven pulley. 
     The spindle  4606  is a substantially columnar member having an axis extending in the rightward/leftward direction. A left end portion of the spindle  4606  is rotatably supported by the bearing  4071   a . A right end portion of the spindle  4606  fits the shaft washer of the bearing  4071   b  and is rotatably supported by the bearing  4071   b . The fourth pulley  4607  is coaxially mounted to the left end portion of the spindle  4606 . A mounting portion  4606 A is provided at the right end portion of the spindle  4606 . The mounting portion  4606 A is provided with a washer and a bolt that penetrates a base portion of the cutting blade  4061  in the rightward/leftward direction. As this bolt is tightened, the mounting portion  4606 A pinches the cutting blade  4061  via the washer. The cutting blade  4061  can be attached to or removed from the mounting portion  4606 A by tightening or removing the bolt. The spindle  4606  is configured to transmit, via the mounting portion  4606 A, a driving force to the cutting blade  4061  connected to the right end portion of the spindle  4606  and can thus rotate the cutting blade  4061 . Incidentally, the spindle  4606  and the mounting portion  4606 A are an example of an output shaft. 
     The second belt  4608  is looped under tension over the third pulley  4605  and the fourth pulley  4607 . A width of the second belt  4608  in the rightward/leftward direction is substantially equal to a width of the third pulley  4605  and a width of the fourth pulley  4607 . The second belt  4608  is an endless belt. A plurality of teeth is formed in an inner peripheral surface of the second belt  4608 . The plurality of teeth extends in the rightward/leftward direction and is parallel to each other. The plurality of teeth is arrayed in a circumferential direction and engages with the plurality of gear teeth formed in an outer peripheral surface of each of the third pulley  4605  and the fourth pulley  4607 . As the second belt  4608  engages with and is looped under tension over the third pulley  4605  and the fourth pulley  4607 , the second belt  4608  can transmit rotation of the third pulley  4605  to the fourth pulley  4607 . 
     As illustrated in  FIGS. 23A and 23B , a lock mechanism  8  includes an engaging member  8 A and a coil spring  8 B. The engaging member  8 A is a substantially columnar member extending in the rightward/leftward direction. The engaging member  8 A is so disposed as to penetrate the gear housing  4650  and the gear case  4065  in the rightward/leftward direction. The engaging member  8 A is disposed between the countershaft  4602  and the spindle  4606  in the frontward/rearward direction. Specifically, the engaging member  8 A penetrates through the through-hole  4041   k  and the through-hole  4041   j . A right end portion of the lock mechanism  8  has a diameter smaller than that of the engaging hole  4042   k  and is engageable with the engaging hole  4042   k . The coil spring  8 B is disposed between a left side surface of the gear housing  4650  and the gear case  4065 . Specifically, a right end portion of the coil spring  8 B abuts the gear case  4065 , and a left end portion of the coil spring  8 B engages with the engaging member  8 A. Thus, the coil spring  8 B is configured to urge the engaging member  8 A in the leftward direction. The engaging member  8 A is an example of an engagement portion. The coil spring  8 B is an example of an urging member. 
     When the motor body  4068 A is in operation, the fan  4068 C rotates to produce a cooling air. The cooling air that has cooled the motor body  4068 A moves within the gear housing  4650  as indicated by an arrow A in  FIG. 22  and is discharged to the outside. 
     An operation performed when a user attaches or removes the cutting blade  4061  before starting or after finishing work will be described. An operator brings the engaging member  8 A into engagement with the fourth pulley  4607 . Specifically, in a state illustrated in  FIG. 23A , the operator presses the left end portion of the engaging member  8 A rightward. Upon the engaging member  8 A being pressed, the engaging member  8 A moves rightward against an urging force of the coil spring  8 B. The right end portion of the engaging member  8 A that has moved rightward engages with the engaging hole  4042   k  ( FIG. 23B ). In this manner, the engaging member  8 A engages with the fourth pulley  4607 . 
     The fourth pulley  4607  that has engaged with the engaging member  8 A becomes nonrotatable so that the mounting portion  4606 A becomes nonrotatable. Retaining a state where the engaging member  8 A is being pressed and the mounting portion  4606 A is nonrotatable, the operator tightens or removes a bolt into or from the mounting portion  4606 A to attach or remove the cutting blade  4061 . Thereafter, upon the operator who has finished work releasing his/her hand from the engaging member  8 A, the engaging member  8 A moves leftward and away from the fourth pulley  4607  due to the urging force of the coil spring  8 B, and the state illustrated in  FIG. 23A  is restored. 
     According to the sixth embodiment described above, as the engaging member  8 A engages with the fourth pulley  4607 , rotation of the spindle  4606  can be stopped at an engaging location away from the spindle  4606 , unlike a known configuration of locking a spindle. Engagement at a location away from the spindle  4606  makes it possible to counter torque exerted on the spindle  4606  with a small force. Accordingly, the engaging member  8 A or the lock mechanism  8  can be constituted by a component with a small load capacity, and the engaging member  8 A or the lock mechanism  8  of a simple and small configuration can be achieved. 
     The engaging location can be provided between the countershaft  4602  and the spindle  4606 . The engaging member  8 A can be disposed between an axis of rotation of the fourth pulley  4607  and an axis of rotation of the third pulley  4605  in the frontward/rearward direction, and an efficient arrangement utilizing spacing of the components can be achieved. 
     The use of the second belt  4608  enables reliable transmission of a rotary force and a driving force. 
     As a side surface of the fourth pulley  4607  and the engaging member  8 A engage with each other, a configuration in which the side surface of the fourth pulley  4607  is efficiently utilized can be achieved. Accordingly, the size of a configuration in the vicinity of the fourth pulley  4607  can be reduced. 
     With the use of the urging force of the coil spring  8 B, the engagement of the fourth pulley  4607  and the engaging member  8 A is released automatically after the user stops pressing the engaging member  8 A. Accordingly, an operation of replacing the cutting blade  4061  can be facilitated efficiently. 
     Thus far, the sixth embodiment has been described. The sixth embodiment is merely illustrative, and it should be appreciated by a person skilled in the art that various modifications can be made to the combinations of the constituent elements of the sixth embodiment and that such modifications also fall within the scope of the present invention. 
     In the sixth embodiment, a plurality of engaging holes  4042   k  is provided. Alternatively, a single engaging hole  4042   k  may be provided. 
     In the sixth embodiment, the engaging member  8 A engages with the engaging hole  4042   k  formed in the side surface portion of the fourth pulley  4607 . The present invention, however, is not limited to this configuration. As illustrated in the following embodiments, a configuration in which an engaging member engages with an outer peripheral surface of a fourth pulley can also be employed. 
     Next, a seventh embodiment will be described with reference to  FIGS. 24A and 24B . Seventh to tenth embodiments described hereinafter are all modifications of the sixth embodiment. In the description of the seventh embodiment, components and members that correspond to the components and the members constituting the sixth embodiment are given reference characters obtained by adding 1000 to the reference characters used in the sixth embodiment, and descriptions thereof will be omitted. 
     A fourth pulley  5607  according to the seventh embodiment is a substantially cylindrical member having an axis extending in the rightward/leftward direction. A plurality of gear teeth is formed in an outer peripheral surface of the fourth pulley  5607 . The plurality of gear teeth extends in the rightward/leftward direction and is arrayed at regular intervals in a circumferential direction. A fourth pulley  5607  has an inner peripheral surface, and this inner peripheral surface fits an outer peripheral surface of a spindle  5606 . No hole is formed in a left side surface portion of the fourth pulley  5607 . The third pulley  5605  is an example of a drive pulley, and the fourth pulley  5607  is an example of a driven pulley. The spindle  5606  and the mounting portion  5606 A are an example of the output shaft. 
     A lock mechanism  108  includes an engaging member  108 A and a coil spring  108 B. The engaging member  108 A is a substantially columnar member extending in the rightward/leftward direction. The engaging member  108 A is so disposed as to penetrate a gear housing  5650  and a gear case  5065  in the rightward/leftward direction. The coil spring  108 B is disposed between a left side surface portion of the gear housing  5650  and the gear case  5065 . Specifically, a right end portion of the coil spring  108 B abuts the gear case  5065 , and a left end portion of the coil spring  108 B engages with the engaging member  108 A. Thus, the coil spring  108 B is configured to urge the engaging member  108 A in the leftward direction. The engaging member  108 A is an example of the engagement portion. The coil spring  108 B is an example of the urging member. 
     The engaging member  108 A according to the seventh embodiment is disposed between a countershaft  5602  and the spindle  5606  in the frontward/rearward direction. The engaging member  108 A is disposed so that the engaging member  108 A can abut the outer peripheral surface of the fourth pulley  5607 . Upon an operator pressing a left end portion of the engaging member  108 A rightward, the engaging member  108 A moves rightward against an urging force of the coil spring  108 B. A right end portion of the engaging member  108 A that has moved rightward abuts the outer peripheral surface of the fourth pulley  5607  and engages with the gear teeth formed in the outer peripheral surface of the fourth pulley  5607 . The fourth pulley  5607  that has engaged with the engaging member  108 A becomes nonrotatable so that the mounting portion  5606 A becomes nonrotatable. 
     Retaining a state where the engaging member  108 A is being pressed and the mounting portion  5606 A is nonrotatable, the operator tightens or removes a bolt into or from the mounting portion  5606 A to attach or remove a cutting blade  4061 . Thereafter, upon the operator who has finished work releasing his/her hand from the engaging member  108 A, the engaging member  108 A moves leftward and away from the fourth pulley  5607  due to the urging force of the coil spring  108 B, and the state illustrated in  FIG. 24A  is restored. 
     In a modification, teeth engageable with the gear teeth in the fourth pulley  5607  may be provided on an outer peripheral surface of the engaging member  108 A. In this case, the engaging member  108 A and the fourth pulley  5607  engage with each other more reliably. Thus, the fourth pulley  5607 , the spindle  5606 , and the mounting portion  5606 A are fixed more firmly. 
     According to the seventh embodiment described above, as the engaging member  108 A engages with the fourth pulley  5607 , rotation of the spindle  5606  can be stopped at an engaging location away from the spindle  5606 , unlike a known configuration of locking a spindle. Engagement at a location away from the spindle  5606  makes it possible to counter torque exerted on the spindle  5606  with a small force. Particularly, of the components that corotate with the spindle  5606 , the engaging member  108 A engages with the outer peripheral surface (gear teeth) of the fourth pulley  5607  that is farthest from a center axis of rotation of the spindle  5606 , and thus the spindle can be locked with a small force. Accordingly, the engaging member  108 A can be constituted by a component with a small load capacity, and the engaging member  108 A or the lock mechanism  108  of a simple and small configuration can be achieved. 
     The engaging location can be provided between the countershaft  5602  and the spindle  5606 . The engaging member  108 A can be disposed between an axis of rotation of the fourth pulley  5607  and an axis of rotation of the third pulley  5605  in the frontward/rearward direction, and an efficient arrangement utilizing spacing of the components can be achieved. In other words, at least a portion of the lock mechanism  108  is located in a space enclosed by the fourth pulley  5607 , the third pulley  5605 , and a second belt  5608 , and thus space-saving can be achieved. 
     The use of the second belt  5608  enables reliable transmission of a rotary force and a driving force. 
     As the gear teeth in the fourth pulley  5607  engage with the engaging member  108 A, the engaging member  108 A can be disposed efficiently by utilizing the space between the fourth pulley  5607  and the third pulley  5605 . Accordingly, the size of a configuration in the vicinity of the fourth pulley  5607  or the third pulley  5605  can be reduced. 
     With the use of the urging force of the coil spring  108 B, the engagement of the fourth pulley  5607  and the engaging member  108 A is released automatically after the user stops pressing the engaging member  108 A. Accordingly, an operation of replacing the cutting blade  4061  can be facilitated efficiently. 
     Next, an eighth embodiment will be described with reference to  FIGS. 25A and 25B  wherein like parts and components are designated by the same reference numerals plus 2000 as those shown in the sixth embodiments to avoid duplicating description. 
     A fourth pulley  6607  according to the eighth embodiment is a substantially cylindrical member having an axis extending in the rightward/leftward direction. A plurality of gear teeth is formed in an outer peripheral surface of the fourth pulley  6607 . The plurality of gear teeth extends in the rightward/leftward direction and is arrayed at regular intervals in a circumferential direction. The fourth pulley  6607  has an inner peripheral surface, and this inner peripheral surface fits an outer peripheral surface of a spindle  6606 . The fourth pulley  6607  is an example of the drive pulley. The spindle  6606  and the mounting portion  6606 A are an example of the output shaft. 
     A lock mechanism  208  includes an engaging member  208 A and a coil spring  208 B. The engaging member  208 A is a substantially columnar member extending in the rightward/leftward direction. The engaging member  208 A is so disposed as to penetrate a gear housing  6650  and a gear case  6065  in the rightward/leftward direction. The engaging member  208 A according to the eighth embodiment is disposed between a countershaft  6602  and the spindle  6606  in the frontward/rearward direction. The engaging member  208 A is disposed so that the engaging member  208 A can abut the outer peripheral surface of the fourth pulley  6607 . A right end portion of the coil spring  208 B abuts a left side surface of the gear housing  6650 . A left end portion of the coil spring  208 B engages with the engaging member  208 A to urge the engaging member  208 A leftward. The engaging member  208 A is an example of an engagement portion. The coil spring  208 B is an example of an urging member. 
     A second pulley  6603  is substantially circular as viewed in a side view in the rightward/leftward direction and has a substantially cylindrical shape with an axis extending in the rightward/leftward direction. A plurality of grooves is formed in an outer peripheral surface of the second pulley  6603 , and the plurality of grooves extends in a circumferential direction. The plurality of grooves in the second pulley  6603  is disposed parallel to each other and arrayed in the rightward/leftward direction in the outer peripheral surface of the second pulley  6603 . The second pulley  6603  is mounted coaxially with the countershaft  6602 . 
     A plurality of through-holes  242   m  is provided in the second pulley  6603 . The plurality of through-holes  242   m  penetrates the second pulley  6603  in the rightward/leftward direction. The plurality of through-holes  242   m  is provided at regular intervals in a circumferential direction. The through-holes  242   m  each have a diameter greater than that of the engaging member  208 A. Therefore, the engaging member  208 A can penetrate through the through-hole  242   m  in the rightward/leftward direction. A groove  242   n  is provided on the left side of the through-hole  242   m . The groove  242   n  is recessed rightward from a left side surface of the second pulley  6603 . The groove  242   n  is annular in shape whose center is coincident with an axis of the second pulley  6603  as viewed in a left side view. The groove  242   n  has a width greater than that of a front end of the engaging member  208 A. A right end portion of the engaging member  208 A is disposed inside the groove  242   n.    
     Upon an operator pressing a left end portion of the engaging member  208 A rightward, the engaging member  208 A moves rightward against an urging force of the coil spring  208 B. The right end portion of the engaging member  208 A that has moved rightward passes through the groove  242   n  and the through-hole  242   m , approaches the outer peripheral surface of the fourth pulley  6607 , and engages with the gear teeth formed in the outer peripheral surface of the fourth pulley  6607  ( FIG. 25B ). 
     The fourth pulley  6607  that has engaged with the engaging member  208 A becomes nonrotatable so that the mounting portion  6606 A becomes nonrotatable. Retaining a state where the engaging member  208 A is being pressed and the mounting portion  6606 A is nonrotatable, the operator tightens or removes a bolt into or from the mounting portion  6606 A to attach or remove a cutting blade  4061 . Thereafter, upon the operator who has finished work releasing his/her hand from the engaging member  208 A, the engaging member  208 A moves leftward and away from the fourth pulley  6607  due to the urging force of the coil spring  208 B, and the state illustrated in  FIG. 25A  is restored. 
     Teeth engageable with the gear teeth in the fourth pulley  6607  may be formed on an outer peripheral surface of the engaging member  208 A. In this case, the engaging member  208 A and the fourth pulley  6607  engage with each other more reliably. Thus, the fourth pulley  6607 , the spindle  6606 , and the mounting portion  6606 A are fixed more firmly. 
     In the eighth embodiment described above, the second pulley  6603  and the fourth pulley  6607  can be so disposed as to overlap each other as viewed in a left side view or a right side view. Accordingly, an arrangement of a transmission mechanism  6060  can be made compact. In addition, an outer diameter of the second pulley  6603  can be increased without being constrained by a position where the engaging member  208 A is disposed. Thus, a reduction ratio of a first pulley (not illustrated) and the second pulley  6603  can be increased. Such a configuration allows for a flexible design of components constituting the transmission mechanism  242 . For example, the fourth pulley can have a smaller diameter. 
     According to the eighth embodiment described above, as the engaging member  208 A engages with the fourth pulley  6607 , rotation of the spindle  6606  can be stopped at an engaging location away from the rotation shaft, unlike a known configuration of locking a spindle. Engagement at a location away from the spindle  6606  makes it possible to counter torque exerted on the spindle  6606  with a small force. Accordingly, the engaging member  208 A can be constituted by a component with a small load capacity, and the engaging member  208 A or the lock mechanism  208  of a simple and small configuration can be achieved. 
     The engaging location can be provided between the countershaft  6602  and the spindle  6606 . The engaging member  208 A can be disposed between an axis of rotation of the fourth pulley  6607  and an axis of rotation of the third pulley  6605  in the frontward/rearward direction, and an efficient arrangement utilizing spacing of the components can be achieved. 
     The use of the second belt  6608  enables reliable transmission of a rotary force and a driving force. 
     As the gear teeth in the fourth pulley  6607  engage with the engaging member  208 A, the engaging member  208 A can be disposed efficiently by utilizing the space between the fourth pulley  6607  and the third pulley  6605 . Accordingly, the size of a configuration in the vicinity of the fourth pulley  6607  or the third pulley  6605  can be reduced. 
     With the use of the urging force of the coil spring  208 B, the engagement of the fourth pulley  6607  and the engaging member  208 A is released automatically after the user stops pressing the engaging member  208 A. Accordingly, an operation of replacing the cutting blade  4061  can be facilitated efficiently. 
     A ninth embodiment will next be described with reference to  FIGS. 26A to 26D , wherein like parts and components are designated by the same reference numerals plus 3000 as those shown in the sixth embodiment for avoiding duplicating description. 
     A lock mechanism  308  according to the ninth embodiment includes an engaging member  308 A and a coil spring  308 B. The engaging member  308 A includes a main body  308 Aa and a holding portion  308 Ab. The engaging member  308 A is an example of the engagement portion. The coil spring  308 B is an example of the urging member. 
     The main body  308 Aa is formed into a rectangular shape as viewed in a front view. The main body  308 Aa is disposed between a third pulley  7605  and a fourth pulley  7607  in the frontward/rearward direction. As illustrated in  FIGS. 26A and 26B , the main body  308 Aa has a front surface that is recessed rearward. This front surface is formed into a substantially circular arc shape that substantially coincides with a shape of an outer periphery of the fourth pulley  7607  as viewed in a side view. The front surface of the main body  308 Aa is further provided with protrusions engageable with gear teeth in the fourth pulley  7607 . The third pulley  7605  is an example of the drive pulley. The fourth pulley  7607  is an example of the driven pulley. 
     The holding portion  308 Ab is fixed to a left side surface of the main body  308 Aa. The holding portion  308 Ab is a rod-shaped member extending in the frontward/rearward direction. The holding portion  308 Ab has a portion extending through a gear housing  7650  in the frontward/rearward direction. A front end of the holding portion  308 Ab is exposed to the outside of the gear housing  7650  and can be held by an operator. 
     The coil spring  308 B is so disposed as to extend in the frontward/rearward direction. A front end of the coil spring  308 B is fixed by a gear case  7065 . A rear end of the coil spring  308 B abuts the main body  308 Aa to urge the main body  308 Aa rearward. 
     In a miter saw according to the ninth embodiment, when attaching or removing a cutting blade  4061 , an operator may pull the holding portion  308 Ab frontward. At this point, the main body  308 Aa bonded to the holding portion  308 Ab moves frontward against an urging force of the coil spring  308 B and engages with the gear teeth formed in the outer peripheral surface of the fourth pulley  7607  ( FIGS. 26C and 26D ). As the engaging member  308 A engages with the fourth pulley  7607 , a spindle  7606  and a mounting portion  7606 A are fixed nonrotatably. As the spindle  7606  and the mounting portion  7606 A become nonrotatable, the cutting blade  4061  can be attached or removed. Thereafter, upon the operator who has finished work releasing his/her hand from the holding portion  308 Ab, the engaging member  308 A moves rearward and away from the fourth pulley  7607  due to the urging force of the coil spring  308 B, and the state illustrated in  FIGS. 26A and 26B  is restored. Incidentally, the spindle  7606  and the mounting portion  7606 A are an example of the output shaft. 
     According to the ninth embodiment described above, as the engaging member  308 A engages with the fourth pulley  7607 , rotation of the spindle  7606  can be stopped at an engaging location away from the spindle  7606 , unlike a known configuration of locking a spindle. Engagement at a location away from the spindle  7606  makes it possible to counter torque exerted on the spindle  7606  with a small force. Particularly, of the components that corotate with the spindle  7606 , the engaging member  308 A engages with the outer peripheral surface (gear teeth) of the fourth pulley  7607  that is farthest from a center axis of rotation of the spindle  7606 , and thus the spindle can be locked with a small force. Accordingly, the engaging member  308 A can be constituted by a component with a small load capacity, and the engaging member  308 A or the lock mechanism  308  of a simple and small configuration can be achieved. 
     The engaging location can be provided between the countershaft  7602  and the spindle  7606 . The engaging member  308 A can be disposed between an axis of rotation of the fourth pulley  7607  and an axis of rotation of the third pulley  7605  in the frontward/rearward direction, and an efficient arrangement utilizing spacing of the components can be achieved. 
     The use of the second belt  7608  enables reliable transmission of a rotary force and a driving force. 
     As the gear teeth in the fourth pulley  7607  engage with the engaging member  308 A, the engaging member  308 A can be disposed efficiently by utilizing the space between the fourth pulley  7607  and the third pulley  7605 . Accordingly, the size of a configuration in the vicinity of the fourth pulley  7607  or the third pulley  7605  can be reduced. 
     With the use of the urging force of the coil spring  308 B, the engagement of the fourth pulley  7607  and the engaging member  308 A is released automatically after the user stops pressing the engaging member  308 A. Accordingly, an operation of replacing the cutting blade  4061  can be facilitated efficiently. 
     A tenth embodiment will next be described with reference to  FIGS. 27A to 27C , wherein like parts and components are designated by the same reference numerals plus 4000 as those shown in the sixth embodiment for avoiding duplicating description. 
       FIG. 27A  is a sectional view illustrating a state where an engaging member  408 A engages with a fourth pulley  8607  in a miter saw according to the tenth embodiment of the present invention. 
       FIG. 27B  is a right side view illustrating a third pulley  8605 , a second belt  8608 , and the engaging member  408 A in a state where the engaging member  408 A engages with the fourth pulley  8607 . 
       FIG. 27C  is a right side view of the third pulley  8605 , the second belt  8608 , and the engaging member  408 A in a state where the engaging member  408 A is spaced apart from the fourth pulley  8607 . In  FIGS. 27B and 27C , a portion of the members is illustrated in a perspective view to facilitate understanding of the structure among the members. 
     As illustrated in  FIGS. 27A to 27C , a lock mechanism  408  according to the tenth embodiment includes the engaging member  408 A and a coil spring  408 B. The engaging member  408 A includes a main body  408 Aa, a holding portion  408 Ab, a rotating shaft  408 Ac, and a protrusion  408 Ad. 
     A gear housing  8650  has an elongated hole  441 Aa formed therein. The elongated hole  441 Aa is positioned in a front end portion of the gear housing  8650 , and extends toward an upper portion of the gear housing  8650  and provides communication between an inside and an outside of the gear housing  8650 . 
     As illustrated in  FIGS. 27A to 27C , the main body  408 Aa is a substantially cylindrical member with its axis extending in the rightward/leftward direction. The protrusion  408 Ad projecting outward in a radial direction of the main body  408 Aa is provided on an outer peripheral surface of the main body  408 Aa. The main body  408 Aa and the protrusion  408 Ad are disposed between the third pulley  8605  and the fourth pulley  8607 . The main body  408 Aa is coaxially bonded to the rotating shaft  408 Ac. The rotating shaft  408 Ac has a cylindrical shape extending in the rightward/leftward direction. A right end portion of the rotating shaft  408 Ac is rotatably supported by a gear cover via a bearing. A left end portion of the rotating shaft  408 Ac is rotatably supported by a gear case  8065  via a bearing. The rotating shaft  408 Ac is bonded to the holding portion  408 Ab at the left end portion of the rotating shaft  408 Ac. 
     The holding portion  408 Ab is a rod-shaped member. The holding portion  408 Ab is so disposed as to penetrate through the elongated hole  441 Aa. One end of the holding portion  408 Ab is fixed to the left end portion of the rotating shaft  408 Ac. Another end of the holding portion  408 Ab is so disposed as to project to the outside and can be held by an operator. 
     A rear end of the coil spring  408 B is fixed to the upper portion of the gear housing  8650 . A front end of the coil spring  408 B is fixed to the holding portion  408 Ab. The coil spring  408 B is configured to urge the engaging member  408 A in a counterclockwise direction, as viewed in a right side view, via the holding portion  408 Ab ( FIGS. 27B and 27C ). In a state where the holding portion  408 Ab is not held, the holding portion  408 Ab which is urged in the counterclockwise direction, as viewed in a right side view, by an urging force of the coil spring  408 B is moved frontward ( FIG. 27C ). In this state, the protrusion  408 Ad is spaced apart from the fourth pulley  8607 . 
     In a miter saw according to the tenth embodiment, when attaching or removing a cutting blade  4061 , an operator pivots the holding portion  408 Ab rearward against the urging force of the coil spring  408 B. At this point, the holding portion  408 Ab pivots clockwise, as viewed in a right side view. As a result, the holding portion  408 Ab pivots rearward, as illustrated in  FIG. 27A . As the holding portion  408 Ab pivots, the main body  408 Aa also pivots clockwise, as viewed in a right side view. As a result, the protrusion  408 Ad approaches the fourth pulley  8607  and engages with the gear teeth in the fourth pulley  8607  ( FIG. 27B ). Thereafter, upon the operator who has finished work releasing his/her hand from the holding portion  408 Ab, the engaging member  408 A pivots counterclockwise, as viewed in a right side view, and away from the fourth pulley  8607  due to the urging force of the coil spring  408 B, and the state illustrated in  FIG. 27C  is restored. 
     As the engaging member  408 A engages with the fourth pulley  8607 , a spindle  8606  and a mounting portion  8606 A are fixed nonrotatably. As the spindle  8606  and the mounting portion  8606 A become nonrotatable, the cutting blade  4061  can be attached or removed. 
     The engaging member  408 A is an example of the engagement portion. The coil spring  408 B is an example of the urging member. The third pulley  8605  is an example of the drive pulley. The fourth pulley is an example of the driven pulley. The spindle  8606  and the mounting portion  8606 A are an example of the output shaft. 
     According to the tenth embodiment described above, as the engaging member  408 A engages with the fourth pulley  8607 , rotation of the spindle  8606  can be stopped at an engaging location away from the spindle  8606 , unlike a known configuration of locking a spindle. Engagement at a location away from the spindle  8606  makes it possible to counter torque exerted on the spindle  8606  with a small force. Accordingly, the engaging member  408 A or the lock mechanism  408  can be constituted by a component with a small load capacity, and the engaging member  408 A or the lock mechanism  408  of a simple and small configuration can be achieved. 
     The engaging location can be provided between the countershaft  8602  and the spindle  8606 . The engaging member  408 A can be disposed between an axis of rotation of the countershaft  8602  and an axis of rotation of the spindle  8606  in the frontward/rearward direction, and an efficient arrangement utilizing spacing of the components can be achieved. 
     The use of the second belt  8608  enables reliable transmission of a rotary force and a driving force. 
     As the gear teeth in the fourth pulley  8607  engage with the engaging member  408 A, the engaging member  408 A can be disposed efficiently by utilizing the space between the fourth pulley  8607  and the third pulley  8605 . Accordingly, the size of a configuration in the vicinity of the fourth pulley  8607  or the third pulley  8605  can be reduced. 
     With the use of the urging force of the coil spring  408 B, the engagement of the fourth pulley  8607  and the engaging member  408 A is released automatically after the user stops pressing the engaging member  408 A. Accordingly, an operation of replacing the cutting blade  4061  can be facilitated efficiently. 
     An urging member of the present invention is not limited to a coil spring. As an alternative to the coil spring used in each embodiment, an urging force can be generated by using various springs, such as a leaf spring or a disc spring, or elastic materials, such as elastomer. The motor body  4068 A is not limited to a commutator motor. For example, it is obvious to a person skilled in the art that the motor body  4068 A can be applied to a power tool having a driving unit, such as a brushless-type motor. It is also apparent to a person skilled in the art that the motor body  4068 A is not limited to a power tool in which a motor is used as a driving source. 
     The engaging members are configured to engage with the fourth pulleys. Alternatively, the engaging members may be configured to engage with the third pulleys. In this case, in order to fix a spindle reliably, it is preferable that a timing belt be looped under tension over a third pulley and a fourth pulley. The fourth pulley can be fixed at a position by the fixing of the third pulley through the employment of the timing belt. 
     Thus far, the present invention has been described on the basis of embodiments. The present invention, however, is not limited to the embodiments described above, and various changes can be made within the scope that does not depart from the spirit of the present invention. 
     REFERENCE SIGNS LIST 
     
         
           1 ,  101 ,  102 ,  201 ,  301 : miter saw,  6 ,  106 ,  107 ,  206 ,  306 : cutting unit,  60 ,  260 : transmission mechanism,  61 : cutting blade,  64 : motor housing,  65 ,  165 ,  265 : gear case,  66 ,  166 ,  266 ,  366 : gear cover,  68 : motor,  68 B: motor shaft,  69   a ,  69   b ,  70   a ,  70   b ,  71   a ,  71   b : bearing,  601 : first pulley,  602 : countershaft,  603 ,  2603 : second pulley,  604 : first belt,  605 : third pulley,  606 : spindle,  606 A: mounting portion,  607 : fourth pulley,  608 : second belt,  652 A,  1652 A: support part,  653 A,  1653 A: support,  655 ,  656 : protrusion,  661 B,  2665 A: support part,  661 C: guide,  662 A: support part,  662 B: guide,  1652 B: guide,  1653 B: guide,  2661 ,  3661 : bearing holder,  2661   a ,  2661   b : stepped portion,  2661   c : stepped portion,  2661   d ,  3661   d : through-hole,  2663 ,  3663 : bearing holder,  2665 : protrusion,  3661   e : notch,  3663 D: projection