Patent Publication Number: US-10766162-B2

Title: Portable machining device

Description:
CROSS-REFERENCE 
     This application claims priority to Japanese patent application serial number 2017-075523, filed on Apr. 5, 2017, the contents of which are herein incorporated by reference in their entirety. 
     TECHNICAL FIELD 
     The present disclosure generally relates to a portable machining device and/or a portable machining tool such as, for example, a portable cutting device used for cutting a material to be cut (workpiece) such as wooden material, etc. 
     BACKGROUND ART 
     A conventional portable machining device generally includes, for example, a base that contacts an upper surface of the workpiece, as well as a machining device main body that is supported on an upper surface side of the base so as to be movable in an up-to-down direction. The machining device generally includes an electric motor, as well as a cutting blade that can rotate via the driving force of the electric motor. By moving the machining device main body in the up-to-down direction with respect to the base, the machining device can be positioned between a cutting position in which the cutting blade protrudes below a lower surface of the base and a retreat position in which the cutting blade retreats in the upward direction with respect to the lower surface of the base. With the rotation of the cutting blade that protrudes below the lower surface of the base and the movement of the machining device with respect to the workpiece, a cutting task can be performed. A cutting blade cover that covers approximately the circumferential periphery of the cutting blade may be provided on the upper surface of the base. A lower portion of the cutting blade that protrudes below the cutting blade cover in the downward direction can cut into the workpiece. The upper periphery of the blade in the cutting position can be covered by the cutting blade cover, which prevents cutting dust from scattering around. 
     This type of the portable machining device generally includes a controller that controls the electric motor. The controller is electrically insulated such that a printed circuit board of the controller is housed in a case having a rectangular plate shape and a shallow bottom, and the interior of the case is resin molded. Various techniques for the arrangement of the controller have been provided in these types of prior art portable machining devices. For example, Japanese Laid-Open Patent Publication No. 2014-79873 discloses a technique in which the controller is housed in an erect manner in the up-to-down direction at the rear of the electric motor. Japanese Laid-Open Patent Publication No. 2015-178226 discloses another technique in which the controller is housed in a slanted manner at the rear of the electric motor. Furthermore, Japanese Laid-Open Patent Publication No. 2014-148015 discloses still another technique in which the controller is housed in a laid-down manner above the electric motor. 
     The above-described techniques, however, have several problems. In Japanese Laid-Open Patent Publication No. 2014-79873, for example, the controller is directed in the upward direction, which interferes with a handle operation. As a result of the controller orientation, the handle has to be accordingly arranged in the upward direction so as avoid interference with handle operation. Additionally, in Japanese Laid-Open Patent Publication No. 2015-178226, the controller obstructs movement of the controller in approaching an operation lever or the base disposed in the vicinity of the controller when the machining main body is moved in the up-to-down direction. Furthermore, in Japanese Laid-Open Patent Publication No. 2014-148015, the handle has to be arranged in the upward direction due to the depth of the controller. Because of these problems, a loss of operability, a loss of handle maneuverability; and/or an increasing size of the products have occurred. 
     Thus, as a result of the mentioned deficiencies in the art, there is a need in the art to house the controller in order to prevent increasing size of the device as well as to improve operability and handle maneuverability. 
     SUMMARY 
     In one exemplary embodiment of the present disclosure, a portable machining device includes a base with which a material to be cut is brought into contact, a machining device main body that is supported above an upper surface of the base, and a handle that is integrally formed with the machining device main body. Furthermore, the machining device main body includes a rotary cutting blade that is rotated by using an electric motor serving as a drive source, the cutting blade configured to be movable in the up-to-down direction so as to be able to protrude below a lower surface of the base such that the cutting blade can perform a cutting task by cutting into a material to be cut. Furthermore, when the protruding length of the cutting blade below the lower surface of the base is at the maximum possible length, a part of a controller for controlling the electric motor is configured to be located behind the handle of the device main body in the front-to-rear direction. 
     According to this embodiment, when the protruding length of the cutting blade below the lower surface of the base is at its maximum, the controller is disposed behind the handle such that the entirety of the controller is not positioned so as to coincide with the entirety of the handle in the front-to-rear direction. Because of this controller arrangement, the operation of maneuverability of the handle is improved. 
     In another exemplary embodiment of the disclosure, the machining device main body is supported so as to be swung in the up-to-down direction via a swing fulcrum that is disposed behind the center of rotation of the cutting blade. When the protruding length of the cutting blade protruding below the lower surface of the base is at its the maximum, the controller is tilted so as to be extending upward from the front to the rear as seen from a side view. Furthermore, a part of the controller is located behind the swing fulcrum in the front-to-rear direction. 
     According to this embodiment, in the machining device in which the machining device main body is supported so as to be swung in the up-to-down direction via the swing fulcrum located behind the rotation center of the cutting blade, a space for housing the controller can be minimized in the front-to-rear direction, with the controller extending upward as described above. Furthermore, interference of the controller with respect to the base can be avoided, and at the same time, an upper moving end of the machining device main body can be positioned further upwards. 
     In another exemplary embodiment of the disclosure, a holding area for inserting a user&#39;s hand to hold the handle is arranged around the handle. Furthermore, a front portion of the controller is configured to overlap with the holding area in the front-to-rear direction, and a rear portion of the controller is also configured to be overlap with the holding area in the up-to-down direction. 
     According to this embodiment, a necessary and sufficient holding area for the user to hold the handle can be obtained and at the same time the controller can be disposed in a compact manner. 
     In another exemplary embodiment of the disclosure, the machining device main body is supported so as to be tiltable with the base in the left-to-right direction. Furthermore, when the machining device main body is situated at a right angle, the controller is configured to be tilted so as to be displaced in a direction approaching the cutting blade extending from the lower to the upper direction as seen from a rear view. 
     According to this embodiment, a space for housing the controller can be minimized in the up-to-down direction. Furthermore, interference of the controller with respect to the base can be avoided, and at the same time, the machining device main body can be tilted in the left-to-right direction at a larger angle. 
     In another exemplary embodiment of the disclosure, a battery pack is attachable to the machining device main body as a power source. Furthermore, when the protruding length of the cutting blade protruding below the lower surface of the base is at its maximum, the battery pack is configured to be disposed behind the electric motor in the front-to-rear direction and below the holding area of the handle in the up-to-down direction. 
     According to this embodiment, since the battery pack is disposed below the holding area of the handle, the battery pack does not interfere with holding of the handle. 
     In another exemplary embodiment of the disclosure, a portable machining device includes a base with which a material to be cut is brought into contact, and also includes a machining device main body that is supported above an upper surface of the base so as to be swung in the up-to-down direction via a swing fulcrum. Furthermore, the machining device main body includes a rotary cutting blade that is rotated by using an electric motor as a drive source, wherein the cutting blade is configured to be movable in the up-to-down direction to protrude below a lower surface of the base such that the cutting blade can perform a cutting task by cutting into a material to be cut. Furthermore, the controller for controlling the electric motor is disposed on a side of the swing fulcrum with respect to the electric motor in the front-to-rear direction. 
     According to this embodiment, the controller is disposed between the electric motor and the swing fulcrum in the front-to-rear direction in a compact manner. In the machining device in which the swing fulcrum is disposed on a front side of the electric motor, the controller is disposed in front of the electric motor. In contrast to this configuration, in the machining device in which the swing fulcrum is disposed on a rear side of the electric motor, the controller is disposed behind the electric motor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a right side view of a portable machining device according to an exemplary embodiment (first embodiment) of the present disclosure, showing a state where a portable machining device main body is situated at an upper standby position 
         FIG. 2  is a left side view of the portable machining device according to the exemplary embodiment (first embodiment), showing a state where the portable machining device main body is moved to an upper end position. 
         FIG. 3  is an overall plan view of the portable machining device according to the exemplary embodiment (first embodiment). 
         FIG. 4  is a right side view of the portable machining device according to the exemplary embodiment (first embodiment), showing a state where the portable machining device main body is moved to a lower end position. 
         FIG. 5  is a left side view of the portable machining device according to the exemplary embodiment (first embodiment), showing a state where the portable machining device main body is moved to a lower end position 
         FIG. 6  is a rear view of the portable machining device according to the exemplary embodiment (first embodiment) as seen from (VI) of  FIG. 4 . 
         FIG. 7  is a longitudinal cross-sectional view of the portable machining device according to the exemplary embodiment (first embodiment), showing a vertical plane passing a rotation center of a cutting blade. 
         FIG. 8  is a left side view of the portable machining device according to the exemplary embodiment (first embodiment), showing a state where the portable machining device main body is moved to the upper end position. This figure shows a right half-split housing of a handle from which a left half-split housing of the handle is removed. 
         FIG. 9  is a perspective view of the portable machining device according to the exemplary embodiment (first embodiment) seen obliquely from the rear left, showing right half-split housings of the handle and a controller housing from which the left half-split housings thereof are removed. 
         FIG. 10  is a rear side view of the portable machining device according to the exemplary embodiment (first embodiment), showing a state where the portable machining device main body is moved to the lower end position and tilted such that a top of the portable machining device main body is moved in a rightward direction. 
         FIG. 11  is a perspective view of a portable machining device according to another embodiment (second embodiment) seen obliquely from the upper left. 
         FIG. 12  is a left side view of the portable machining device according to another embodiment (second embodiment), showing a state where the portable machining device main body is moved to a lower end position. 
         FIG. 13  is a longitudinal cross-sectional view of the portable machining device according to another embodiment (second embodiment), showing a vertical plane passing a rotation center of a cutting blade. 
         FIG. 14  is an overall perspective view of the portable machining device according to another embodiment (third embodiment). 
         FIG. 15  is a right side view of the portable machining device according to another embodiment (third embodiment). 
         FIG. 16  is a left side view of the portable machining device according to another embodiment (third embodiment), showing an interior of a handle. 
         FIG. 17  is a left side view of the portable machining device according to another embodiment (third embodiment), showing a state where the portable machining device main body is held at an upper end position. This figure also shows an interior of the handle. 
         FIG. 18  is a cross-sectional view taken along line (XVIII)-(XVIII) of  FIG. 16 , showing a longitudinal sectional view of an electric motor. 
         FIG. 19  is a cross-sectional view taken along line (XIX)-(XIX) of  FIG. 16 , showing a lateral sectional view of the electric motor. 
         FIG. 20  is a right side view of the portable machining device according to another embodiment (third embodiment), showing a state where a right side cutting blade cover is removed from the portable machining device main body. This figure also shows a state where a guide member is returned to a retreat position and a holding member is situated at a holding position. 
         FIG. 21  is a right side view of the guide member and its surroundings. This figure also shows a state where the guide member is moved to a guiding position and the holding member is situated at a holding release position. 
         FIG. 22  is a cross-sectional view taken along line (XXII)-(XXII) of  FIG. 21 , showing the holding member and its surroundings. 
         FIG. 23  is a cross-sectional view taken along line (XVIII)-(XVIII) of  FIG. 21 , showing the guide member and its surroundings. 
         FIG. 24  is an overall perspective view of the portable machining device according to another embodiment (third embodiment), showing a state where the portable machining device is placed on a long ruler. 
         FIG. 25  is a plan view seen from an arrow (XXV) of  FIG. 24 , showing a connecting portion of two long rulers. 
         FIG. 26  is a plan view of the connecting portion. 
         FIG. 27  is a cross-sectional view taken along line (XXVII)-(XXVII) of  FIG. 25 , showing a lateral sectional view of the long rulers and the connecting portion. 
         FIG. 28  is a perspective view of the portable machining device, seen from a lower surface of a base. 
     
    
    
     DETAILED DESCRIPTION 
     The detailed description set forth below, when considered with the appended drawings, is intended to be a description of exemplary embodiments of the present invention and is not intended to be restrictive and/or to represent the only embodiments in which the present invention can be practiced. The term “exemplary” used throughout this description means “serving as an example, instance, or illustration,” and should not necessarily be construed as preferred or advantageous over other exemplary embodiments. The detailed description includes specific details for the purpose of providing a thorough understanding of the exemplary embodiments of the invention. It will be apparent to those skilled in the art that the exemplary embodiments of the invention may be practiced without these specific details. In some instances, these specific details refer to well-known structures, components and/or devices that are shown in block diagram form in order to avoid obscuring significant aspects of the exemplary embodiments presented herein. 
     Representative, non-limiting embodiments according to the present disclosure will be described with reference to  FIGS. 1 to 10 . In the embodiments, a cutting device such as a circular saw, which a user holds and operates to perform a cutting task, is exemplified as a portable machining device  1 . In the following embodiments, the forward and rearward directions of members and configurations may be described relative to the direction in which a cutting task of the portable machining device  1  is performed. In particular, the direction in which the portable machining device  1  proceeds to cut a workpiece is referred to as the front side. Thus, the user may be situated on the rear side of the portable machining device  1 . Furthermore, the leftward and rightward directions of the members may be described relative to the user&#39;s position at the rear of the device, facing the device. 
     As shown in  FIGS. 1 to 3 , the portable machining device  1  may be referred to as a so-called plunge circular saw, which generally includes a base  2  that is brought into contact with an upper surface of a workpiece W as well as a machining device main body  10  that is supported on an upper surface side of the base  2 . The base  2  may have an approximately rectangular flat-plate shape. A lower surface of the base  2  may be a contact surface  2   a  that is brought into contact with the workpiece W. A cutting blade cover  20  may be supported on an upper surface side of the base  2 . A front support portion  25  and a rear support portion  26  may be provided on the upper surface of the base  2  at a forward position and a rearward position, respectively. The front support portion  25  and the rear support portion  26  may be provided parallel to each other in an erected manner. The cutting blade cover  20  may be supported so as to be tiltable in the left-to-right direction via the front support portion  25  and the rear support portion  26 . 
     As shown in  FIGS. 2 and 3 , a rear portion of the machining device main body  10  may be supported on a left side of the cutting blade cover  20  via a main body support shaft  19  about which the machining device main body  10  can be swung in the up-to-down direction. The main body support shaft  19  may be disposed to the rear of the center of rotation, spindle  3  (see  FIG. 7 ), of the cutting blade  11 . Thus, the cutting blade  11  may be largely moved in the up-to-down direction within the cutting blade cover  20 . The machining device main body  10  may be biased to swing in an upward direction by a compression spring  18  that is interposed between the machining device main body  10  and the base  2 . As shown in  FIG. 2 , the machining device main body  10  may be held at an upper end position (standby position) by the biasing force of the compression spring  18 . A lower portion of the cutting blade  11  may protrude below the contact surface  2   a  of the base  2  in the downward direction when the machining device main body  10  is swung about the main body support shaft  19  in the downward direction against the biasing force of the compression spring  18 .  FIGS. 4 to 6  show a state upon swinging the machining device main body  10  in the downward direction, where the protruding length of the cutting blade  11  below the contact surface  2   a  of the base  2  reaches its maximum (where the machining device main body  10  reaches a lower end position). By moving the portable machining device  1  in the forward direction while this lowermost protruding state of the cutting blade  11  is being held, the cutting blade  11  can cut into the workpiece W from the blade&#39;s front end and a cutting task can be performed. Instead of moving in the forward direction, if the machining device main body  10  is swung in the downward direction while the cutting blade  11  rotates, driven by the driving force of electric motor  12 , the lower portion of the rotating cutting blade  11  may protrude below the contact surface  2   a  of the base  2  so as to enter downwards into the workpiece W when performing a cut, where said cut is referred to as a plunge cut. 
     The machining device main body  10  may be supported by the cutting blade cover  20  that in turn can be maneuvered to tilt in the left-to-right direction via the front support portion  25  and the rear support portion  26 . Because of this configuration, the cutting blade  11  within the cutting blade cover  20  can also consequently be tilted with respect to the base  2  in the left-to-right direction.  FIG. 10  shows a state where the machining device main body  10  is tilted in the rightward direction by approximately 45°. By tilting the cutting blade  11  in the leftward/rightward direction, the portable machining device  1  can be used to perform an oblique cut into the workpiece W A tilt angle of the cutting blade cover  20 , and in turn that of the cutting blade  11  within the cutting blade cover  20 , may be indicated and measured by lines demarcating angles on an angle scale provided on the front support portion  25  (see  FIG. 2 ). A tilt position of the cutting blade cover  20 , and by consequence that of the cutting blade  11 , with respect to the base  2  can be adjusted as desired to a particular angle by fastening the fixing screws  21 ,  22 . 
     The cutting blade cover  20  may cover the upper region of the cutting blade  11  above contact surface  2   a , which prevents cutting dust from scattering. A dust collection port  20   a  used for connecting a dust collection hose or a dust collection box may be provided at the rear of the cutting blade cover  20 . As a result, cutting dust blown out in the proximity of a cutting position (cut-out position by the cutting blade  11 ), where said dust is generated by rotation of the cutting blade  11  and contact with a workpiece, may flow in the rearward direction, and consequently said cutting dust may be collected through the dust collection port  20   a . As shown in  FIGS. 1 and 4 , an arrow  20   b  showing the rotation direction of the cutting blade  11  may be indicated on the right surface side of the cutting blade cover  20 . 
     A swing position (swing angle) of the machining device main body  10  can be fixed to a lower end position or an arbitrary position during a swing operation so as to not be further movable in the downward direction by fastening a fixing screw  23  provided on the left surface side of the cutting blade cover  20  as shown in  FIGS. 2 and 8 . By adjusting the swing position of the machining device main body  10  and fixing the swing position in the up-to-down direction by using the fastening screw  23 , the protruding length of the cutting blade  11  below the contact surface  2   a  can thereby be fixed to an arbitrary and/or a predetermined length. Because of this adjustment, the cutting depth of the cutting blade  11  with respect to the workpiece W can be adjusted and fixed to an arbitrary and/or a predetermined length. As shown in  FIGS. 2 and 8 , a cutting depth scale  24  for indicating the cutting depth of the cutting blade  11  may be provided on the left surface side of the cutting blade cover  20 . 
     As shown in  FIG. 7 , the machining device main body  10  may be provided with the electric motor  12  that serves as the driving source for and rotates the cutting blade  11 . The machining device main body  10  may also be provided with a reduction gear portion  13  that houses a reduction gear train for decreasing rotation output of the electric motor  12  in a gear case  13   a , and a handle  14  that a user holds. The electric motor  12  may be connected to the left side of the reduction gear portion  13 . 
     A DC brushless motor that is powered by a battery pack  15  (DC power source) serving as a power source can be used as the electric motor  12 . The electric motor  12  may be provided with a stator  12   b  that is fixed to a motor case  12   a , as well as a rotor  12   c  that is rotatably supported on an inner circumference of the stator  12   b . A sensor PCB  12   g  including an electromagnetic sensor for detecting a rotation position of the rotor  12   c  may be attached to the rear surface (left surface) of the stator  12   b  in a direction of a motor axis J. A motor shaft  12   d  that is joined to the rotor  12   c  may be rotatably supported around the motor axis J via a right bearing  12   h  and a left bearing  12   i . The right bearing  12   h  may be held in the gear case  13   a  and the left bearing  12   i  may be held in an intermediate partition wall  12   j  of the motor case  12   a.    
     A cooling fan  12   f  may be attached to the motor shaft  12   d . As shown in  FIGS. 2, 5 and 8 , a plurality of intake holes  12   e  may be provided on the left side of the motor case  12   a . When the electric motor  12  is driven, the cooling fan  12   f  attached to the motor shaft  12   d  may rotate synchronously with the motor shaft  12   d . Due to the rotation of the cooling fan  12   f , outside air may be introduced into the motor case  12   a  via the intake holes  12   e . Outside air which flows into the motor case  12   a  may flow in the rightward direction (in the direction of the motor axis J toward the cutting blade  11 ), cooling the stator  12   b , the rotor  12   c  and the sensor PCB  12   g , etc. A ventilation hole  12   k  may be provided on the motor case  12   a  on the lateral side of the cooling fan  12   f  (at the front/rear side of the fan) as shown in  FIGS. 7 and 9 . Outside air (motor cooling air) that has cooled the interior of the motor case  12   a  may flow into a controller housing  30  via the ventilation hole  12   k . Outside air which flows into the controller housing  30  may be used for cooling the controller  31 , which will be discussed in detail infra. 
     Rotation output of the electric motor  12  may be decreased through the reduction gear portion  13  and then transferred to the spindle  3 . The spindle  3  may protrude into the interior of the cutting blade cover  20  through an arc-shaped insertion groove hole  20   c  provided on the left side of the cutting blade cover  20 . Furthermore, a tip end of the spindle  3  protruding into the interior of the cutting blade cover  20  may be attached to the circular cutting blade  11 . The center of rotation of the cutting blade  11  may be fixed by use of a cutting blade fixing screw  3   a  that can be firmly fastened and fixed to the tip end surface of the spindle  3 . The spindle  3  may be rotatably supported by the gear case  13   a  via a right bearing  3   b  and a left bearing  3   c.    
     As shown in  FIG. 9 , a battery attachment portion  16  may be provided on the front side of the motor case  12   a . Similarly, a battery attachment portion  17  may be provided on the rear side of the motor case  12   a . The battery attachment portions  16  and  17  may be used for attaching battery packs  15  at the front or back of the motor case  12   a , respectively.  FIG. 8  shows a state where the battery packs  15  are removed from the battery attachment portions  16  and  17 . Each of the front battery attachment portion  16  and the rear battery attachment portion  17  may be configured such that a slide-attachment-type battery pack  15  can be attached thereto. In more detail, the front battery attachment portion  16  may be provided with a pair of upper and lower rails  16   a . Furthermore, positive and negative battery terminals may be arranged between the pair of upper and lower rails  16   a . Similarly, the rear battery attachment portion  17  may be provided with a pair of upper and lower rails  17   a , and positive and negative battery terminals may be arranged between the pair of upper and lower rails  17   a . The battery packs  15  may be attached by being slid into each of the front and rear battery attachment portions  16  and  17 , respectively, in the rightward direction. On the contrary, the battery pack  15  may be detached from each of the front and rear battery attachment portions  16  and  17  by being slid in the leftward direction while a removal button  15   a  provided on the left end of the battery pack  15  is concomitantly pressed. 
     A lithium ion battery may be used as the battery pack  15  in which a plurality of lithium ion battery cells are housed in a battery case having an approximately hexahedral shape. The battery pack  15  may be highly versatile such that it can be attached to other electric power tools, other than the portable machining device  1 . By sliding the hexahedrally-shaped battery pack  15  in the direction of the motor axis J toward and away from the cutting blade  11 , the battery pack  15  can be attached to and removed from each of the battery attachment portions  16  and  17 , respectively. When the battery packs  15  are removed from the battery attachment portions  16  and  17 , they can be recharged by a dedicated battery charger, such that they can be repeatedly used. 
     As shown in  FIGS. 3 and 7 , a residual capacity display portion  27  for showing residual capacity of the battery backs  15  and a variable speed dial  28  for finely adjusting a rotational speed of the electric motor  12  may be provided on the upper surface of the motor case  12   a.    
     As shown in  FIG. 9 , a controller housing  30  may be provided on the right side of the rear battery attachment portion  17  at the rear of the electric motor  12 . The controller housing  30  may have a box shape extending from the rear of the motor case  12   a  in the rearward direction. As shown in  FIG. 2 , the controller housing  30  may be configured such that when the machining device main body  10  is positioned at its upper end position, the controller housing  30  extends approximately horizontally from the rear of the motor case  12   a  in the rearward direction along and to the rear of the upper rearmost surface of the base  2 . Because of this configuration, as shown in  FIG. 5 , when the machining device main body  10  is moved to its lower end position, the rear side of the controller housing  30  may be directed counterclockwise upward and forward in a tilting manner in the upward direction. A controller  31  for mainly controlling the electric motor  12  may be housed in the controller housing  30 . In the present embodiment, features as to the position of the controller  31  in the controller housing  30  are devised, which will be discussed in more detail infra. 
     The handle  14  that the user holds may have a loop shape straddling the upper portion of the motor case  12   a  of the electric motor  12  as well as the rear upper surface of the controller housing  30 . A front portion of the handle  14  may be joined to the upper surface of the motor case  12   a  and a rear portion of the handle  14  may be joined to the rear upper surface of the controller housing  30 . An inner circumference of the handle  14  having the loop shape may have a sufficient space (holding area S) in a manner such that the user can insert their hand into the area so as to grip/hold the handle  14 . A trigger-type switch lever  9  which may be pulled inwards by a user&#39;s fingertips may be provided on the underside of the inner periphery of the handle  14 . As shown in  FIG. 8 , a main switch  6  may be housed in the handle  14  at the rear of the switch lever  9  in a pulling direction of the switch lever  9 . When the switch lever  9  is pulled, the main switch  6  may be switched on, starting to drive electric motor  12 . When the electric motor runs, the cutting blade  11  may begin to rotate. 
     A front grip  8  may be provided at the front portion of the handle  14 . As shown in  FIGS. 3, 6 and 7 , the front grip  8  may extend from the front portion of the handle  14  in the leftward direction. The user can easily move and operate the portable machining device  1  in a more stable manner by holding the handle  14  with one hand and the front grip  8  with another hand. A lock off lever  7  may be provided on the upper surface of the handle  4 . When the lock off lever  7  is not in a forward position, the switch lever  9  may be locked in an off position so as to not be able to be pulled. In contrast, when the lock off lever  7  is slid to the forward position with, for example, a thumb of the user&#39;s hand that holds the handle  14 , the switch lever  9  may be able to be pulled inward by the user&#39;s fingertips. 
     The controller  31  may have a rectangular plate shape and may house a control circuit board in a case having a shallow bottom. The interior of the case may be resin molded. The controller  31  may include a control circuit for mainly controlling the electric motor  12  and a power supply circuit. In more detail, the control circuit may include a microprocessor that transmits a control signal based on positional information of the rotor  12   c  that is detected by the sensor PCB  12   g  of the electric motor  12 . Furthermore, the controller  31  may also include a drive circuit composed of FETs that switches the current of the electric motor  12  based on the control signal received from the control circuit. Furthermore, the controller  31  may also include an auto-stop circuit that interrupts power supply to the electric motor  12  based on a detection result from the battery pack  15  in order to prevent over-discharging and over-current conditions. 
     As shown in  FIGS. 8 and 9 , the rectangular flat-shaped controller  31  may be housed in the controller housing  30  in a tiltable manner mainly in the left-to-right direction. As shown in  FIG. 8 , in the present embodiment (first embodiment), when the machining device main body  10  is moved to its upper end position, the controller  31  may be situated so as to be fixed approximately horizontal in the front-to-rear direction but tiltable in the left-to-right direction such that the top portion of the controller  31  may approach the side of the cutting blade  11  (in a direction in which the controller  31  is tilted toward the rightward direction from a right angle with regard to the base  2 ). Because of this configuration, as shown in  FIG. 9 , when the machining device main body  10  is moved to its lower end position, the controller  31  may be tilted in the front-to-rear direction as well as in the left-to-right direction. 
     Furthermore, when the machining device main body  10  is moved to its lower end position, the entirety of the controller  31  may be situated to be offset rearwards from a location where the handle  14  (the holding area S) extends in the front-to-rear direction. In this way, the controller  31  may be arranged to be tiltable in the front-to-rear direction as well as in the left-to-right direction and in the up-to-down-direction without interference. In other words, the controller  31  may be tilted in a compound manner. Because of this configuration, the height of the handle  14  may be restricted and at the same time sufficient holding space (holding capability) can be obtained. 
     Furthermore, the machining device main body  10  may be supported so as to be swung in the up-to-down direction about the main body support shaft  19  (swing fulcrum) that is located to the rear of the center of rotation of the cutting blade  11  (to the rear of the spindle  3 ). Furthermore, the controller  31  may be arranged to be offset in the rearward direction with respect to the main body support shaft  19 . Because of this configuration, as shown in  FIG. 5 , when the protruding length of the cutting blade  11  protruding below the lower surface of the base  2  is at its maximum, the controller  31  may be tilted about the main body support shaft  19  so as to be displaced counterclockwise in the forward and upward direction as seen from the side view of  FIG. 5 . Because of this configuration, the space for housing the controller  31  (controller housing  30 ) can be made to be compact in the front-to-rear direction. Furthermore, while being compact, interference of the controller housing  30  or the controller  31  with respect to the base  2  is avoided, and also the machining device main body  10  is maneuverable to be swung to a larger angle in the upward or left-to-right direction to decrease the protruding length of the cutting blade  11  protruding below the lower surface of the base  2 . 
     Furthermore, the holding area S for inserting the user&#39;s hand to hold the handle  14  may be arranged surrounding the handle  14  (mainly around the underside of the lower periphery of the handle  14 ). The controller  31  may be housed in the controller housing  30  in a tiltable manner such that the front portion of the controller  31  may overlap with the holding area S in the front-to-rear direction and the rear portion of the controller  31  may overlap with the holding area S in the up-to-down direction. Because of this configuration, a necessary and sufficient holding area S to hold the handle  14  (for obtaining a sufficient holding capability of the handle  14 ) can be obtained, while at the same time the controller  31  can be arranged in a compact and maneuverable manner. 
     The machining device main body  10  may be supported so as to be tiltable with respect to the base  2  via the front support portion  25  and the rear support portion  26 . As shown in  FIG. 6 , when the machining device main body  10  is situated at a right angle position with respect to the base  2 , the controller  31  may be placed in a tilted manner in the controller housing  30  so as to be displaced in a direction approaching the cutting blade  11  (in the rightward direction) from the down-to-up viewing direction as seen from the rear view of  FIG. 6 . Because of this arrangement of the controller  31 , the controller housing  30  can be made to be compact in the left-to-right direction. Furthermore, as shown in  FIG. 10 , when the machining device main body  10  is tilted in the rightward direction, interference of the controller housing  30  with respect to the base  2  can be avoided and thus this compact configuration enables the machining device main body  10  to be tilted at a larger angle in the rightward direction. 
     Furthermore, as shown in  FIG. 5 , when the protruding length of the cutting blade  11  protruding below the lower surface of the base  2  is at its maximum, each of the battery packs  15  may be respectively disposed at the front and the rear, respectively, of the electric motor  12  below the holding area S of the handle  14 . Because of this configuration, when the user holds the handle  14 , the battery packs  15  do not interfere with the user&#39;s operation. 
     As shown in  FIGS. 7 and 9 , the interior of the controller housing  30  may be in fluid communication with the interior of the motor case  12   a  of the electric motor  12  through the ventilation hole  12   k  provided adjacent to the cooling tan  12   f . Because of this configuration, the motor cooling air may flow into the interior of the controller housing  30  through the ventilation hole  12   k . The motor cooling air passing through the ventilation hole  12   k  may be blown out to the controller  31 , which can cool the controller  31 . The motor cooling air that has cooled the controller  31  may be further discharged to the outside through an exhaust hole  32  provided on the right side of the controller housing  30 , as shown in  FIG. 6 . In this way, the controller  31  in which heat generation sources such as switching elements are mounted can be efficiently cooled by use of sourcing the motor cooling air from the cooling fan  12   f.    
     According to the portable machining device  1  of the present embodiment (first embodiment) as discussed above, the controller  31  having the rectangular flat-plate shape may be arranged at the rear of the electric motor  12  and at the same time to be offset in the rearward direction with respect to the holding area. S of the handle  14 . Because of this configuration of the controller  31 , sufficient holding area S (holding capability) can be obtained and at the same time the height of the handle  14  may be restricted. 
     Furthermore, the controller  31  may be housed in the controller housing  30  in a compound tilting manner so as to be tilted concomitantly in the front-to-rear direction, in the up-to-down direction and in the left-to-right direction. Because of this configuration of the controller  31 , the controller housing  30  can be made to be compact and as a result interference of the controller housing  30  with respect to the base  2  can be avoided, and thus the machining device main body  10  is able to be swung at a greater range of angles in the up-to-down left-to-right directions. 
     The embodiment discussed above may be further modified without departing from the scope and spirit of the present teachings.  FIGS. 11 to 13  show the portable machining device  1  of the second embodiment. The portable machining device  1  of the second embodiment may differ from that of the first embodiment in that the portable machining device  1  of the second embodiment performs the feature of radio communication with incidental devices such as a dust collector etc. The portable machining device  1  of the second embodiment may have the same members and configurations of that of the first embodiment such as the arrangement of the controller  31  etc. Descriptions of the members and configurations in common with the first embodiment may be omitted by using the same reference numerals. 
     In the second embodiment, a rear cover  12   m  may be provided on the left side of the motor case  12   a . A radio communication unit  40  may be provided on the inside of the rear cover  12   m . A communication adapter  41  may be attached to the radio communication unit  40 . An adapter insertion portion  42  for inserting the communication adapter  41  may be provided on the left end surface of the rear cover  12   m . The adapter insertion portion  42  may comprise a rectangular hole and penetrate deep in the rightward direction in the motor case along below the residual capacity display portion  27 . As shown in  FIG. 13 , an adapter receiving portion  44  may be incorporated at the innermost part of the adapter insertion portion  42 . By inserting the communication adapter  41  into the adapter insertion portion  42  to connect to the adapter receiving portion  44 , the radio communication unit  140  may be able to conduct radio communication between the portable machining device  1  and an incidental device such as the dust collector  50  via the communication adapter  41 . The adapter insertion portion  42  may be covered by a cap  43 . By inserting the communication adapter  41  into the adapter insertion portion  42  and closing the cap  43 , the communication adapter  41  and the adapter receiving portion  44  may be shielded against dust, in a dustproof configuration. 
     The communication adapter  41  may have been previously associated (paired) with a communication adapter of the specific incidental device such as the dust collector  50  such that radio communication between the two can take place. In a state where the communication adapter  41  is attached to the radio communication unit  40 , when the switch lever  9  is switched on to run (start) the portable machining device  1 , the start information from the portable machining device  1  may be transmitted through radio communication to the side of the dust collector  50 , based on which the dust collector  50  may automatically run. As shown in  FIG. 12 , by attaching a dust collection hose  51  to the dust collection port  20   a , the dust collector  50  may be an incidental device of the portable machining device  1 , and the dust collector  50  may be in a standby state when powered on. 
     As discussed above, the portable machining device  1  may be provided with a radio communication function to communicate with the dust collector  50  as an incidental device with regard to, mainly, start and stop operations. Accordingly, the dust collector  50  may automatically start/stop in accordance with a start/stop operation of the portable machining device  1 , which can furthermore improve operability and workability of both the portable machining device  1  and the dust collector  50 . 
     Further, a third embodiment of the portable machining device  100  will be explained. As shown in  FIGS. 14 to 17 , the portable machining device  100  of the third embodiment may be provided with a base  102  that is brought into contact with the upper surface of the workpiece W as well as a machining device main body  110  that is supported on an upper surface side of the base  102 . The base  102  may have an approximately rectangular flat-plate shape. A lower surface of the base  102  may be a contact surface  102   a  that is brought into contact with the workpiece W. A cutting blade cover  120  may be supported on an upper surface side of the base  102 . A front support portion  125  and a rear support portion  126  may be provided on the upper surface of the base  102  at a forward position and a rearward position, respectively. The front support portion  125  and the rear support portion  126  may be provided parallel to each other in an erect manner. The cutting blade cover  120  may be supported so as to be tiltable in the left-to-right direction via the front support portion  125  and the rear support portion  126 . 
     As shown in  FIGS. 16 and 17 , the machining device main body  110  may be supported on the left side of the cutting device cover  120  via a main body support shaft  119  about which the machining device main body  110  can swung in the up-to-down direction. A cutting blade  111  may be moved in the up-to-down direction within the cutting blade cover  120  in accordance with an up-to-down movement of the machining device main body  110 . The machining device main body  110  may be biased to swing in an upwards direction by a compression spring  117  that is interposed between the machining device main body  110  and the cutting blade cover  120 . As shown in  FIG. 17 , the machining device main body  110  may be held at an upper end position (standby position) by a biasing three of the compression spring  117 . A lower portion of the cutting blade  111  may protrude below the contact surface  102   a  of the base  102  in the downward direction when the machining device main body  110  is swung about the main body support shaft  119  in the downward direction against the biasing force of the compression spring  117 . By moving the portable machining device  100  in the forward direction while this lowermost protruding state of the cutting blade  111  is being held, the cutting blade  111  can cut into the workpiece W from the blade&#39;s front end and a cutting task can be performed. Instead of moving in the forward direction, if the machining device main body  110  is swung in the downward direction while the cutting blade  111  rotates, driven by the driving force of electric motor  112 , the lower portion of the rotating cutting blade  111  may protrude below the contact surface  102   a  of the base  102  so as to enter downwards into the workpiece W when performing a cut. 
     The machining device main body  110  may be supported by the cutting blade cover  120  that in turn can be maneuvered to tilt in the left-to-right direction via the front support portion  125  and the rear support portion  126 . Because of this configuration, the cutting blade  111  within the cutting blade cover  120  can also consequently be tilted with respect to the base  102  in the left-to-right direction. By tilting the cutting blade  111  in the leftward/rightward direction, the cutting blade  111  can be used to perform an oblique cut into the workpiece W. A tilt angle of the cutting blade cover  120 , and in turn that of the cutting blade  111  within the cutting blade cover  120 , may be indicated and measured by lines demarcating angles on an angle scale  123  provided in the front support portion  125  (see  FIG. 17 ). A tilt position of the cutting blade cover  120 , and by consequence that of the cutting blade  111  with respect to the base  102  can be adjusted as desired to a particular angle by fastening the fixing screw  122 . 
     The cutting blade cover  120  may cover the upper region of the cutting blade  111  above the contact surface  2   a , which prevents cutting dust from scattering. A dust collection port  120   a  used for connecting a dust collection hose or a dust collection box may be provided at the rear of the cutting blade cover  120 . As a result, cutting dust blown out in the proximity of a cutting position (cut-out position by the cutting blade  111 ), where said dust is generated by rotation of the cutting blade ill and contact with the workpiece W, may flow in the rearward direction, and consequently said cutting dust may be collected through the dust collection port  120   a . As shown in  FIGS. 14 and 15 , an arrow  120   b  showing the rotation direction of the cutting blade  111  may be indicated on the right surface side of the cutting blade cover  120 . 
     A swing position (swing angle) of the machining device main body  110  can be fixed to a lower end position or an arbitrary position during a swing operation so as to not be further movable in the downward direction by fastening a fixing screw  121  provided on the left surface side of the cutting blade cover  120 . By adjusting the swing position of the machining device main body  110  and fixing the swing position in the up-to-down direction by use of the fastening screw  121 , the protruding length of the cutting blade  111  below the contact surface  102   a  can thereby be fixed to an arbitrary and/or a predetermined length. Because of this adjustment, the cutting depth of the cutting blade  111  with respect to the workpiece W can be adjusted and fixed to an arbitrary and/or a predetermined length. As shown in  FIG. 17 , a cutting depth scale  124  for indicating the cutting depth of the cutting blade  111  may be provided on the left surface side of the cutting blade cover  120 . 
     As shown in  FIG. 18 , the machining device main body  110  may be provided with the electric motor  112  that serves as the driving source for and rotates the cutting blade  111 . The machining device main body  110  may also be provided with a reduction gear portion  113  that houses a reduction gear train for decreasing rotation output of the electric motor  112  in a gear case  13   a , and a handle  114  that a user holds. The electric motor  112  may be connected to the left side of the reduction gear portion  113 . 
     A DC brushless motor that is powered by a battery pack (DC power source) sewing as a power source can be used as the electric motor  112 . The electric motor  112  may be provided with a stator  112   b  that is fixed on a side of a motor case  112   a  as well as a rotor  112   c  that is rotatably supported on an inner circumference of the stator  112   b . A sensor PCB  112   g  including an electromagnetic sensor for detecting a rotation position of the rotor  112   c  may be attached to the rear surface (left surface) of the stator  112   b  in a direction of a motor axis J. A motor shaft  112   d  that is joined to the rotor  112   c  may be rotatably supported around the motor axis J via a right bearing  112   h  and a left bearing  112   i . The right bearing  112   h  may be held in the gear case  113   a  and the left bearing  112   i  may be held in a center left wall of the motor case  112   a.    
     A cooling fan  112   f  may be attached to the motor shaft  112   d . As shown in  FIGS. 16 and 17 , a plurality of intake holes  112   e  may be provided on the left side of the motor case  112   a . When the electric motor  112  is driven, the cooling fan  112   f  attached to the motor shaft  112   d  may rotate synchronously with the motor shaft  112   d . Due to the rotation of the cooling fan  112   f , outside air may be introduced into the motor case  112   a  via the intake holes  112   e . Outside air which flows into the motor case  112   a  may flow in the rightward direction (in the direction of the motor axis J toward the cutting blade  111 ), cooling the stator  112   b , the rotor  112   c  and the sensor PCB  112   g , etc. A ventilation hole  112   j  may be provided on the motor case  112   a  on the lateral side of the cooling fan  112   f  (at the front/rear side of the fan) as shown in  FIG. 19 . Outside air (motor cooling air) that has cooled the interior of the motor case  112   a  may flow into the interior of the handle  114  via the ventilation hole  112   j . Outside air which flows into the handle  114  may be used for cooling the controller  106 , which will be discussed in detail infra. 
     Rotation output of the electric motor  112  may be decreased through the reduction gear portion  113  and then transferred to the spindle  103 . The spindle  103  may protrude into the interior of the cutting blade cover  120  through an arc-shaped insertion groove hole  120   c  provided on the left side of the cutting blade cover  120 . Furthermore, a tip end of the spindle  103  protruding into the interior of the cutting blade cover  120  may be attached to the circular cutting blade  111 . The center of rotation of the cutting blade  111  may be fixed by use of a cutting blade fixing screw  103   a  that can be firmly fastened and fixed to the tip end surface of the spindle  103 . The spindle  103  may be rotatably supported by the gear case  113   a  via a right bearing  103   b  and a left bearing  103   c.    
     As shown in  FIGS. 16 and 17 , the handle  114  may have a loop shape straddling the upper portion of the motor case  112   a  as well as the rear portion thereof. A trigger-type switch lever  109  which may be pulled inwards by a user&#39;s fingertips may be provided on an inner circumference side (lower surface side) of the handle  114 . When the switch lever  109  is pulled, the electric motor  112  may run and the cutting blade  115  may rotate. 
     As shown in  FIGS. 14 to 17 , a power supply portion  116  for attaching a battery pack  115  may be provided on the rear side of the handle  114 . The battery pack  115  may be mechanically and electrically connected to the power supply portion  116  by being slid into said portion in the rightward direction with respect to the power supply portion  116 . In contrast, the battery pack  115  may be detached from the power supply portion  116  by being slid out from said portion in the leftward direction, from the right to left. The battery pack  115  that is used for the previous operations can be recharged after being detached from the power supply portion  116  by a dedicated battery charger, such that it may be repeatedly used. The battery pack  115  may be a lithium ion battery within which a plurality of battery cells are incorporated. The battery pack  115  may be attached to an electric power tool such as an electric screwdriver, etc. 
     As shown in  FIGS. 16 and 17 , a controller  106  mainly used for controlling the electric motor  112  may be incorporated in the rear of the handle  114  between the power supply portion  116  and the rear surface of the motor case  112   a  in the front-to-rear direction. The controller  106  may be configured such that a control circuit board on which electric components including a capacitor  106   a  etc. are mounted, is housed in a case having a rectangular plate shape and a shallow bottom, wherein the interior of the case is resin molded. As shown in  FIG. 16 , the controller  106  may be vertically held in the up-to-down direction. The controller  106  may control the electric motor  112 , the motor&#39;s rotation speed, and/or also perform an auto-stop based on current overload or over-discharge information detected from the battery pack  115 . Additionally, an adjustment dial  108  for adjusting the rotation speed of the electric motor  112  may be provided behind the controller  106 . 
     As shown in  FIG. 19 , the aforementioned ventilation hole  112   j  may be disposed to the front of the controller  106 . Motor cooling air may flow into the interior of the handle  114  through the ventilation hole  112   j . The motor cooling air that flows into the handle  114  through the ventilation hole  112   j  may flow further to the controller  106 . Because of this flow path of cooling air, the controller  106  may be cooled. After cooling the controller  106 , the air can continue along its flow path to be discharged to the outside from an exhaust hole  107  provided on the right side of the handle  114 .  FIG. 19  shows a thick solid line depicting the flow path of the motor cooling air from the ventilation hole  112   j  to the exhaust hole  107 . In this way, by being present in this flow path, the controller  106 , in which heat generation sources such as the capacitor  106   a  etc. are mounted may be effectively cooled by use of the motor cooling air. 
     A front grip  104  may be provided at the front of the handle  114 . As shown in  FIG. 14 , the front grip  104  may extend from the front portion of the handle  114  in the leftward direction. The user may hold the handle  114  with one hand and the front grip  114  with their other hand in order to easily operate the portable machining device  100  in a stable manner. A hexagon wrench  118  may be inserted into and held on the right side of the front grip  104 . The aforementioned fixing screw  103   a  for fixing the cutting blade  111  may be fastened and/or loosened by use of the hexagon wrench  118 . In this way, the detachable hexagon wrench  118  which can be used for exchanging the cutting blade  111  may be held on the front grip  104 , which in turn can improve convenience. 
     A cutting blade guide  130  for assisting smooth rotation of the cutting blade  111  may be provided behind the cutting blade  111 . The cutting blade guide  130  may include a guide member  131  as well as a holding member  135 . The guide member  131 , which is referred to as a wedge knife or a riving knife, may function in such a manner as to be inserted into a cutting groove C immediately after a cutting task is performed in order to hold the width of the cutting groove C to approximately the width of the cutting blade  111 , as shown in  FIG. 21 . Because of the presence of the guide member  131 , the width of the cutting groove C may be held in a constant manner and thus a smooth finish by the cutting blade  111 , wherein the presence of said guide member  131  reduces rotational resistance encountered when the cutting blade  111  contacts the workpiece W. As a result, cutting accuracy can be improved. 
     As shown in  FIG. 20 , the guide member  131  may be supported behind the cutting blade  111  in the front-to-rear direction on the inner side of the rear portion of the cutting blade cover  120 . Furthermore, the guide member  131  may be provided so as to be rotatable in the up-to-down direction about a support shaft  132 . The guide member  131  may be moved between a retracted position shown in  FIG. 20  and a guiding position shown in  FIG. 21 . 
     The guide member  131  may be made of a thin steel plate with approximately the same width as that of the cutting blade  111 , and its rotation tip end at its outer radial end may be formed in a semicircular shape. As shown in  FIG. 23 , the guide member  131  may be biased by a first biasing member  133  such that the rotation tip end of the guide member  131  moves in the downward direction (counterclockwise direction in  FIG. 20 ). A torsion spring may be used as the first biasing member  133 . When the guide member  131  is moved (taken out) to the guiding position shown in  FIG. 21  by the biasing force of the first biasing member  133 , the rotation tip end (lower end) of the guide member  131  may be inserted (enter) into the cutting groove C immediately after the cutting. By inserting the guide member  131 , which has approximately the same width as that of the cutting blade  111 , into the cutting groove C, the cutting groove C can be fixedly held at a width approximately as wide as that of the cutting blade  111 . 
     As shown in  FIG. 20 , the guide member  131  may be held by the holding member  135  in the retraction position where the guide member  131  rotates clockwise in the upward direction. The holding member  135  may be provided to the front of the guide member  131  so as to be rotatable in the up-to-down direction about a support shaft  136 . The holding member  135  may be provided so as to be rotatable between a hold-release position shown in  FIG. 21  and a hold position shown in  FIG. 20  via the support shaft  136 . As shown in  FIG. 22 , the holding member  135  may be biased by a second biasing member  137  in a direction in which the holding member  135  rotates from the hold-release position shown in  FIG. 21  to the hold position shown in  FIG. 20  (in the counterclockwise direction). 
     A torsion spring may be used as the second biasing member  137 , wherein the biasing force of said spring is larger than that of the first biasing member  133 . As shown in  FIG. 20 , a holding engaging portion  135   a  extending in the rearward and upward directions may be integrally formed with the holding member  135 . Corresponding to the holding engaging portion  135   a , an engaging receiving portion  131   a  may be integrally formed with the front portion of the guide member  131 . The engaging receiving portion  131   a  may engage with the lower portion of the holding engaging portion  135   a . Because of this engagement configuration, as shown in  FIG. 21 , in a state where the holding member  135  is disposed in the hold-release position against the biasing force of the second biasing member  137 , the holding engaging portion  135   a  may be retracted in the upward direction and concomitantly, the engaging receiving portion  131   a  may also be allowed to move in the upward direction. As a result, the guide member  131  may be moved (taken out) to the guiding position by the biasing force of the first biasing member  133 . 
     In contrast, as shown in  FIGS. 20-23 , in a state where the holding member  135  is moved to the hold position by the biasing force of the second biasing member  137 , the holding engaging portion  135   a  may be moved in the downward direction rotating counter-clockwise and concomitantly the engaging receiving portion  131   a  may be pushed in the downward direction, rotating clockwise. As a result, the guide member  131  may be returned to the retraction position against the biasing force of the first biasing member  133 . 
     As shown in  FIG. 20 , when the holding member  135  is moved to the hold position by the biasing force of the second biasing member  137 , the rotation tip end at the outer radial length of the holding member  135  (detection portion  135   b ) may protrude below the contact surface  102   a  of the base  102 . A rotation end position of the holding member  135  in a direction toward the hold position by the biasing force of the second biasing member  137  may be restricted by a stopper  138 . In more detail, the stopper  138  may be positioned such that the detection portion  135   b  of the holding member  135  does not rotate further past a predetermined extent in the counterclockwise direction, where the maximum extent of rotation for the detection portion  135   b  is the vertical downward pointing direction perpendicular to the contact surface  102   a  of the base  102 , where the rotation tip end of the holding member  135  is displaced a little in the rearward direction. Because of this configuration, when the contact surface  102   a  of the base  102  is brought into contact with the upper surface of the workpiece W and then the detection portion  135   b  of the holding member  135  is brought into contact with the upper surface of the workpiece W, which pushes upward in turn on the holding member  135 , the holding member  135  may rotate to the hold-release position against the biasing force of the second biasing member  137  as shown in  FIG. 21 . This is because the weight of the portable machining device  100  contributing to the force of the workpiece W pushing upward on the holding member  135  is larger than the biasing force of the second biasing member  137 . Furthermore, in a cutting task where the cutting blade  111  cuts into a front end portion of the workpiece W, the end portion of the workpiece W may be brought into contact with the detection portion  135   b  as the portable machining device  100  moves further forward. In this state of contact of the workpiece W with the detection portion  135   b , the portable machining device  100  may be moved forward in the cutting proceeding direction and concomitantly the holding member  135  may rotate to the hold-release position against the biasing force of the second biasing member  137  as shown in  FIG. 21 . 
     When the holding member  135  rotates to the hold-release position, a pressed-down state of the engaging receiving portion  131   a  caused by the holding engaging portion  135   a  may be released. As a result, the guide member  131  may be moved (taken out) to the guiding position (in a vertical direction intersecting the contact surface  102   a ) by the biasing force of the first biasing member  133 , in the counter-clockwise direction. By inserting the guide member  131 , the width of which is approximately the same as the cutting blade  111 , into the cutting groove C of the workpiece W, the groove width of the cutting groove C may be held to be the same width as that immediately after it has been cut by the cutting blade  111 . Because of this feature of the guide member  131 , rotational resistance encountered due to the width of cutting groove C becoming smaller post-cutting, may be restricted, and thus smooth rotation of the cutting blade  111  can be obtained to perform the cutting task precisely. 
     When the contact surface  102   a  of the base  102  is spaced away from the upper surface of the workpiece W by, for example, lifting the portable cutting device  100  up from the workpiece W after the cutting task is finished, the pressed-up state of the detection portion  135   b  caused by the force of workpiece W pushing upwards on the detection portion  135   b  may be released, and thus the holding member  135  may be returned to the hold position shown in  FIG. 20  by the restoring biasing force of the second biasing member  137 . In a process where the holding member  135  returns to the hold position, the engaging receiving portion  131   a  may be pressed down by the holding engaging portion  135   a  as the holding engaging portion  135   a  moves in the counter-clockwise direction and thus the guide member  131  may automatically returned to the retraction position shown in  FIG. 20  against the biasing force of the first biasing member  133  when the portable cutting device  100  is lifted up from the workpiece W. In this way, when unused for its guiding function, the guide member  131  can automatically return to the retraction position along the upper surface of the base  102  (in a direction where the guide member  131  may not protrude on the side of the contact surface  102   a ). In the retraction position, the guide member  131  along its longitudinal direction may be disposed along the upper surface of the base  102 . Additionally, when the guide member  131  is held in the retraction position, the guide member  131  at its radially outward longitudinal end does not protrude below the contact surface  102   a . Because of this configuration, damage of other members caused by interference thereof with respect to the workpiece W may be previously prevented. 
     According to the portable machining device  100  of the present embodiment as discussed above, as to the cutting blade guide  130 , both the rotation center of the guide member  131  (support shaft  132 ) and the rotation center of the holding member  135  (support shaft  136 ) may be located behind (to the rear and left of) the cutting blade  111 . Furthermore, the range of rotation of the guide member  131  as well as that of the holding member  135 , in the area to the rear and left of the cutting blade  111  and beneath the base  102  may be relatively small. Because of this configuration, in comparison to a conventional device in which this type of the guide member provided in a cutting device main body is moved together in an up-to-down movement of the cutting device main body, an overall movement area of the guide member  131  may be reduced and thus compact structure of the cutting blade cover  120  can be obtained, while at the same time reducing rotational resistance as described above. 
     A conventional guide member disclosed in, for example, European Patent Publication No. 2638995, is configured to be supported on the side of the cutting device main body and is configured to be moved in the up-to-down direction together with the cutting blade within the cutting blade cover. When the conventional guide member is moved together with the cutting blade in the up-to-down direction, a space for movement may be needed in the cutting blade cover. As a result, the cutting blade cover may be enlarged and compact structure thereof may become difficult. Furthermore, a guide member disclosed in, for example, Japanese Laid-Open Patent Publication No. 2014-04723, is configured to be fixed to a guide position protruding below a lower surface of the base and not to be moved in the up-to-down direction and thus a space for movement may not be (originally) needed in the cutting blade cover. According to the exemplified embodiment of the present teaching, a compact structure of the cutting blade cover can be obtained by improving a supporting configuration of the guide member. 
     By use of the portable machining device  100 , the user can perform a cutting task by directly contacting the contact surface  102   a  of the base  102  towards the workpiece W. Additionally, when cutting, for example, aluminum composite material etc. or performing a groove cutting, a long ruler  140  may be placed on the upper surface of the workpiece W and the portable machining device  100  may be also placed on the long ruler  140  such that it may slide along the ruler  140  to perform such a cutting as shown in  FIG. 24 . By using the long ruler  140 , it may be possible to precisely and accurately cut the workpiece W over a long distance. 
     The long ruler  140  may have the following features that conventional devices do not possess. The long ruler  140  may have a configuration where a front-side first ruler  141  is combined to a rear-side second ruler  142 . The first ruler  141  and the second ruler  142  may be mutually combined to each other via a ruler connection member  143 . Both the first ruler  141  and the second ruler  142  may be made of drawn aluminum. 
     A first rail  141   a  and a second rail  141   b  for guiding the portable machining device  100  may be provided on the upper surface of the first ruler  141 . Similarly, a first rail  142   a  and a second rail  142   b  may be provided on the second ruler  142 . The first rails  141   a  and  142   a  may be formed to be rectangular in cross section having a recessed groove shape and convex in the upward direction (open in the downward direction). Corresponding to this, as shown in  FIG. 28 , a rail receiving portion  102   b  for receiving the first rails  141   a  and  142   a  may be provided on the contact surface  102   a  of the base  102 . The rail receiving portion  102   b  may be formed to be recessed and rectangular in cross section and extend from the front end to the rear end of the base, having sufficient width and depth such that the first rails  141   a  and  142   a  can be firmly inserted thereto without rattling. 
     The second rails  141   b  and  142   b  may be formed to be rectangular in cross section having a recessed groove shape and may be configured to be open in the upward direction. That is, the second rails  141   b  and  142   b  may be disposed upside down with respect to the first rails  141   a  and  142   a . The second rails  141   b  and  142   b  may also be disposed parallel to the first rails  141   a  and  142   a . Furthermore, groove width of the second rails  141   b  and  142   b  may be the same as that of the first rails  141   a  and  142   a . As shown in  FIG. 24 , the second rails  141   b  and  142   b  may be provided to be spaced adjacent to the immediate left of the left edge of the base  102  and extend therealong. Furthermore, as shown in  FIG. 27 , engaging edges  141   c  and  142   c  may be provided on the right side of the second rails  141   b  and  142   b . Corresponding to this configuration, as shown in  FIG. 28 , an engaging plate  102   c  for preventing the portable machining device  100  from falling down may be provided on the left side of the base  102 . The engaging plate  102   c  has adjustable fixable length in the left-to-right direction, and may be fixed in either one of the locations so as to extend from the left edge of the base  102  or so as not to extend therefrom. As shown in  FIG. 27 , by extending the engaging plate  102   c  outward (to the left) relative to the left edge of the base  102 , and thereby inserting the engaging plate  102   c  into the lower side of the engaging edge  141   c  and  142   c  in a state where the portable machining device  100  is placed on the long ruler  140 , the portable machining device  100  can be prevented from falling down. As shown in  FIG. 28 , a sliding plate  102   d  for improving sliding ability with respect to the long ruler  140  may be attached to the contact surface  102   a  of the base  102 . By improving sliding ability of the base  102  with respect to the long ruler  140  by use of the sliding plate  102   c , the portable machining device  100  can be easily moved and thus operability of the portable machining device  100  for performing a cutting task can be improved. 
     As shown in  FIG. 25 , the first ruler  141  and the second ruler  142  may be joined to each other by inserting ruler connection members  143  between the first rails  141   a  and  142   a  and the second rails  141   b  and  142   b , respectively.  FIG. 26  shows the ruler connection member  143  in detail. Each of the ruler connection members  143  may have a connection main body  144  and four connection fixing members  145 . Four housing recesses  144   a  may be provided at approximately equal intervals on one surface side of the connection main body  144 . A positioning recess  144   b  may be provided on the rear left side of each housing recess  144   a . Each positioning recess  144   b  may extend from the housing recess  144   a  in the rearward direction and have the same depth as that of the housing recess  144   a.    
     Each of the four connection fixing members  145  may be housed in the housing recess  144   a  and fixed thereto by a fixing screw  146 . A protrusion  145   a  extending in the rearward direction may be provided on the rear left side of each connection fixing member  145 . Each protrusion  145   a  may be housed in the positioning recess  144   b . All of the connection fixing members  145  may be disposed in the same direction by positioning each of the protrusions  145   a  in the corresponding positioning recess  144   b.    
     As shown in  FIG. 27 , a flat head screw may be used as the fixing screw  146 . A screw insertion hole  145   b  for inserting the fixing screw  146  may be provided in each connection fixing member  145 . Four screw holes  144   c  for fastening the fixing screw  146  may be provided on the connection main body  144 . The width of the connection main body  144  may be configured so as to be smaller than a length between vertical left and right walls of the first rails  141   a ,  142   a  and between vertical left and right walls of the second rails  141   b ,  142   b . Because of this configuration, the ruler connection member  143  may be easily inserted to and retracted from the first rails  141   a ,  142   a  and the second rails  141   b ,  142   b.    
     The screw insertion hole  145   b  of each connection fixing member  145  may be formed as an oblong hole shape slightly longer in the left-to-right direction than in the front-to-rear direction. Because of this configuration, each of the connection fixing members  145  may be displacably supported within the housing recess  144   a  in the left-to-right direction. Furthermore, when the fixing screw  146  is fastened to the screw hole  144   c , a right end of the connection fixing member  145  (a side opposite to the protrusion  145   a ) may protrude from the right edge of the connection main body  144  and may be pressed by the right-side vertical wall of the first rails  141   a ,  142   a , or the second rails  141   b , and  142   b  due to the tapered-shaped seat surface of the screw head. In this way, the right end of the four connection fixing member  145  may be pressed to the right-side vertical wall of the rails. As a result, a left end of the connection main body  144  may be pressed by the left-side vertical wall. 
     The two ruler connection members  143  as discussed above may be inserted between the first rail  141   a  of the first ruler  141  and the first rail  142   a  of the second ruler  142  as well as between the second rail  141   b  of the first ruler  141  and the second rail  142   b  of the second ruler  142 . As shown in  FIG. 27 , the two ruler connection members  143  may be inserted so as to be disposed upside down facing opposite in the up-to-down direction relative to each other. The first ruler  141  and the second ruler  142  may be joined so as to be flush with each other in the front-to-rear direction by the two ruler connection members  143  that are inserted into and fixed to the first ruler  141  and the second ruler  142 . Because of this configuration, continuity of the long ruler  140  can be obtained. By utilizing the long-sized long ruler  140  in which the first ruler  141  and the second ruler  142  are joined via the ruler connection members  143 , a long-sized workpiece W can be cut at a stretch. In this respect, a cutting task can be efficiently performed. 
     Regarding the conventional connection structures of the long ruler, German Utility Model Publication No. 202013104555 discloses that a connection member on which a plurality of magnets are attached is used for connecting two rulers due to attracting force of the magnet. Furthermore, European Patent Publication No. 1892056 discloses that a plurality of fixing screws provided on the connection member are butted against a bottom surface of the two rails in a strut manner to connect the two rails. However, according to these conventional connection structures, it may be difficult to prevent rattling or positional displacement of the rail portions with respect to the connection member in the left-to-right direction in a reliable manner. As a result, the combined two long rulers may be offset to each other in the left-right front-rear plane. 
     In this respect, according to the connection structure of the ruler connection members  143  in the present teaching as discussed above, each ruler connection member  143  may be fixed securely in a strut manner in the left-to-right direction within the first rails  141   a ,  142   a  and the second rails  141   b ,  142   b  such that the connection main body  144  and the connection fixing member  145  are displaced in opposite directions to be respectively pressed to the left and right vertical walls of the rails, due to the fastening force of the fixing screws  146 . Because of this configuration, the ruler connection member  143  may be fixed without rattling in the left-to-right direction. As a result, the first ruler  141  and the second ruler  142  may be joined without rattling in the left-right front-rear plane. Alternatively, one of the two ruler connection members  143  may be omitted. 
     The present embodiment discussed above may be further modified without departing from the scope and spirit of the present teachings. In the exemplified cutting blade guide  130 , the guide member  131  is configured to be held in the retraction position by the holding member  135 . Instead, the holding member  135  may be omitted. In this case, the guide member  131  may be held in the retraction position by, for example, engaging the guide member  131  with a bolding protrusion or inserting/removing a holding pin through manual operation. 
     Furthermore, in the exemplified portable machining device  100 , the machining device main body  110  may be moved in the up-to-down direction with respect to the cutting blade cover  120 . Instead, the exemplified cutting blade guide  130  may be applied to the machining device in which the cutting blade cover is fixed to the machining device main body. 
     Furthermore, without limiting the portable machining device  100  in which a saw blade is attached as the cutting blade  111 , the exemplified cutting blade guide  130  may be applied to another blade, such as a cutting device having a grooving cutter. Furthermore, in the above-discussed embodiment, the portable machining device  100  operated by the battery pack  115  is exemplified. Instead, the exemplified cutting blade guide  130  may be applied to the cutting device operated by a commercial AC power source.