Abstract:
A digital miter saw for cutting a workpiece includes a base, a member supported on the base and moveable relative to the base, and a cutting member moveable with the member. A detector is provided for detecting at least one of a miter angle and a bevel angle between the cutting member and the workpiece, and for outputting a signal indicative of the at least one detected angle, and a digital controller is provided which has an interface operable to receive the signal.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a continuation of U.S. application Ser. No. 10/960,719, filed Oct. 8, 2004, the contents of which are incorporated herein by reference.  
         [0002]     This application is based upon and claims the benefit of priorities from Japanese Patent Application No. 2003-350157 filed on Oct. 8, 2003 and Japanese Patent Application No. 2004-217997 filed on Jul. 26, 2004, the entire disclosures of which are hereby incorporated by references in its entirety. 
     
    
     BACKGROUND OF THE INVENTION  
       [0003]     1. Field of the Invention  
         [0004]     The present invention relates to a miter saw capable of adjusting the angle of a circular saw blade in relation to its base and the angle of the circular saw blade in relation to a contact surface of a fence fixed to the base.  
         [0005]     2. Description of the Related Art  
         [0006]     Conventional miter saws include a base for supporting a workpiece, a cutter blade portion for rotatably supporting a circular saw blade, and a supporting unit for pivotably supporting the circular saw blade about a pivoting shaft that is substantially parallel to the axis of the circular saw blade. The supporting unit can be inclined with respect to the base so that the angle formed by the side surfaces of the circular saw blade and the top surface of the base can be adjusted.  
         [0007]     Further, if the miter saw is provided with a turntable along with the base for supporting a workpiece, the turntable is coupled with the supporting unit so that the angle of the side surfaces of the circular saw blade in relation to the top surface of the base can be adjusted.  
         [0008]     Further, when the angle of the side surfaces of the circular saw blade can be adjusted with respect to the contact surface of the fence fixed to the base, a support for pivotably supporting the cutter blade portion is coupled with the turntable rotatably provided on the top surface of the base so that the support can rotate about the rotational axis of the turntable.  
         [0009]     The user of the miter saw can cut the workpiece supported on the top surface of the base in a slanting direction by adjusting the angle of the side surfaces of the circular saw blade in relation to the top surface of the base. And the user can cut a workpiece at a slant in relation to the side surface of the workpiece opposing the contact surface of the fence in a vertical direction by adjusting the angle of the side surfaces of the circular saw blade in relation to the contact surface of the fence. The user performs these adjustments while referencing graduated scales integrally provided on the supporting unit and the base or turntable for indicating degree of tilt and degree of rotation. Hence, the user of this type of miter saw can be aware of the inclination angle and rotation angle by viewing the graduated scales. However, it is not easy to learn the angles of inclination and rotation instantaneously. Further, due to space restrictions, there is a restriction on the number of angle values that can be inscribed on the graduated scales. Hence, the user cannot easily learn the current angles of inclination and rotation instantaneously for angular values other than those inscribed on the graduated scales, leading to a potential drop in work efficiency.  
         [0010]     Japanese unexamined patent application publication No. 2000-254817 discloses a miter saw having detecting means for detecting the inclination angle of a rotary face of a circular saw relative to a base, and a display for displaying the angle detected by this detecting means.  
         [0011]     The miter saw disclosed in Japanese unexamined patent application publication No. 2000-254817 has a detection shaft coupled with the rotating shaft that supports the rotary face of the circular saw and detects the rotation angle of the detection shaft. Hence, the miter saw detects the rotation angle by counting the rotation angle of the detection shaft using a rotary encoder, for example, and displays this detected rotation angle.  
         [0012]     The miter saw described above detects the inclination angle for the rotary face of the circular saw relative to the top surface of the base and displays this detected angle on the display, enabling the user to know the current inclination angle instantaneously. However, the displayed inclination angle is always detected based on an initial reference position. The rotation angle of the turntable with respect to the base is similarly always detected and displayed based on an initial reference position.  
         [0013]     Usually, the miter saw is configured so that a portion of the base or turntable mechanically engages with the supporting unit to fix the circular saw. Therefore, the saw&#39;s sides can form a right angle to the top surface of the base, the most frequently used position, or form an inclination angle of 45° to the top surface of the base, the second most commonly used position.  
         [0014]     The miter saw is further configured such that the base and a portion of the turntable engage together mechanically to fix the rotational position of the turntable with respect to the base. Therefore, the side surfaces of the circular saw blade can form a right angle to the contact surface of the fence, the most commonly used position, or form a rotation angle of 15°, 30°, 45°, or 60° with the contact surface of the fence, the next most commonly used positions.  
         [0015]     Further, even when a display is provided for displaying the detected angles, the display may not always be used due to malfunctions, various working conditions, or the user&#39;s preference. Hence, a graduated scale is also often provided along with the supporting unit or base for indicating commonly used inclination angles and rotation angles as well as the display.  
         [0016]     In the miter saw having the above construction, the inclination angle and rotation angle is always detected based on a preset reference point. Therefore, the angle displayed on the display often deviates from the angle determined by a mechanical engagement at a predetermined position or an angle indicated by the graduated scale due to errors in detection or imprecision in the dimensions of the miter saw.  
         [0017]     For example, in a miter saw having a maximum inclination range of 45°, the display may show 44° or 46° although the user has tilted the supporting unit to 45°. Further, when the base and turntable are mechanically engaged at such predetermined angles as 15°, 30°, 45°, or 60°, the display may show a different angle from these settings. When this happens, the user is provided with multiple values for the angle, inviting confusion that may lead to a decline in working efficiency.  
         [0018]     Further, even when the supporting unit is mechanically engaged with the base or turntable at a predetermined position, vibrations or other external forces may cause the angle displayed on the display to change undesirably.  
         [0019]     If the angles of inclination and rotation are detected over a broad range, errors in the detected angle may be large, since the angles are always detected based on a preset reference position. Hence, it is difficult to display accurate angles of inclination and rotation.  
       SUMMARY OF THE INVENTION  
       [0020]     In view of the foregoing, it is an object of the present invention to provide a miter saw that can provide suitable angle information to a user.  
         [0021]     It is another object of the present invention to provide a miter saw capable of reducing errors in detecting angles during angle adjustments.  
         [0022]     The present invention provides a miter saw comprising: a base for mounting a workpiece thereon; a movable member supported to the base and movable relative to the base; a cutter blade portion connected to the movable member for rotatably supporting a circular saw blade to cut the workpiece; a positioning portion associated with the movable member and providing a predetermined nominal position of the movable member with respect to the base, the predetermined nominal position including a reference position and a specific position; a detector for producing an output signal indicative of a position of the movable member with respect to the base; a display for displaying a moving amount of the movable member from the reference position; and a processor for setting an angle between the reference position and the predetermined nominal position as the moving amount when the movable member is positioned at the predetermined nominal position. The processor computes the moving amount based on the output signal from the detector when the movable member is positioned at a position other than the predetermined nominal position. The processor sends data indicative of the moving amount to the display.  
         [0023]     The present invention provides a miter saw comprising: a base for mounting a workpiece thereon; a movable member supported to the base and movable relative to the base; a cutter blade portion connected to the movable member for rotatably supporting a circular saw blade to cut the workpiece; a positioning portion associated with the movable member and providing a predetermined nominal position of the movable member with respect to the base, the predetermined nominal position including a reference position and a specific position; a detector for producing an output signal indicative of a position of the movable member with respect to the base; a display for displaying a moving amount of the movable member from the reference position; a storage for storing a table providing a relationship between the predetermined nominal position and an output signal of the detector when the turntable is positioned at the predetermined nominal position; and a processor for computing a measured angle from the reference position on the basis of the output signal from the detector and searching the predetermined nominal position from the table based on the measured angle. The processor sends data indicating the searched predetermined nominal position to the display. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]     The above and other objects, features, and advantages of the invention will become more apparent from reading the following description of the preferred embodiments taken in connection with the accompanying drawings in which:  
         [0025]      FIG. 1  is a side view showing a miter saw according to a first embodiment of the present invention;  
         [0026]      FIG. 2  is a circuit diagram showing a controller for a display used in the miter saw of the preferred embodiment;  
         [0027]      FIG. 3  is an enlarged side view showing a first inclination state of the miter saw in  FIG. 1 ;  
         [0028]      FIG. 4  is an enlarged right side view showing a second inclination state of the miter saw in  FIG. 1 ;  
         [0029]      FIG. 5  is an enlarged cross-sectional view showing a first rotation state of the miter saw in  FIG. 1 ;  
         [0030]      FIG. 6  is an enlarged cross-sectional view showing a second rotation state of the miter saw in  FIG. 1 ;  
         [0031]      FIGS. 7, 8 , and  9  are flowcharts illustrating control operations for the display in  FIG. 2 ;  
         [0032]      FIGS. 10 through 15  are diagrams showing output pulses generated by a rotary encoder used in the miter saw in  FIG. 1 ,  
         [0033]      FIG. 16  is a side view showing a miter saw according to a second embodiment of the present invention;  
         [0034]      FIG. 17  is a bottom view of the miter saw in  FIG. 16 ;  
         [0035]      FIG. 18  is a partial enlarged bottom view of the miter saw in  FIG. 16 ;  
         [0036]      FIG. 19  is a side view of the miter saw in  FIG. 16  in which the turntable is engaged with the base;  
         [0037]      FIG. 20  is an enlarged view of the miter saw in FIG.  16 ; and  
         [0038]      FIG. 21  is a side view of the miter saw in  FIG. 16  in which the turntable is movable with respect to the base. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0039]     Next, a miter saw according to a preferred embodiment of the present invention will be described while referring to the accompanying drawings.  FIG. 1  shows a miter saw  10  according to the preferred embodiment of the present invention.  
         [0040]     As shown in  FIG. 1 , the miter saw  10  includes a base unit  20  that is disposed on a flat surface for supporting a workpiece made of wood on the top surface thereof; a cutting unit  30  for cutting the workpiece; and a supporting unit  40  for supporting the cutting unit  30  in a manner that the cutting unit  30  can be moved from an upper position to a lower position to cut down the workpiece. The supporting unit  40  can also be tilted with respect to the top surface of the base unit  20 .  
         [0041]     The base unit  20  includes a base  21  placed directly on the flat surface, a turntable  22  that can rotate angularly with respect to the base  21 , and a fence  23  having a contact surface  23   a  that contacts a side surface of a workpiece on the top surface of the base  21  for holding the position of the workpiece. The turntable  22  has a rotational axis substantially orthogonal to the top surface of the base  21 , and is capable of rotating about the rotational axis within a horizontal plane that includes the top surface of the base  21 . A potentiometer  50  is provided between the turntable  22  and the base  21  for detecting the rotation angle of the turntable  22  with respect to the base  21 . In the following description, the front side of the miter saw refers to the direction in which the contact surface  23   a  of the fence  23  faces; the bottom side of the miter saw refers to the side facing the flat surface on which the base is placed; and the left-to-right direction refers to the direction along which the fence  23  extends.  
         [0042]     The cutting unit  30  includes a cutter blade  31  for cutting the workpiece, the cutter blade  31  having a rotational axis  31   a ; and a holder  32  for supporting the cutter blade  31  in order to rotate the cutter blade  31  about the rotational axis  31   a.    
         [0043]     The supporting unit  40  is coupled to the turntable  22  movably. The turntable  22  has a rotational axis  24  integral therewith. The supporting unit  40  has one end which is pivotably coupled to the rotational axis  24  in order to tilt about the rotational axis  24  with respect to the turntable  22 . On the other end of the supporting unit  40 , a pivoting axis  41  extends substantially parallel to the rotational axis  31   a  of the cutter blade  31 . The cutting unit  30  is joined to the supporting unit  40  through the rotational axis  24  so that the cutting blade  31  can pivot about the pivoting axis  41 . A potentiometer  60  is provided on the turntable  22  and the supporting unit  40  for detecting the inclination angle of the supporting unit  40  with respect to the turntable  22 .  
         [0044]     A tilting guide  42  is formed near one end of the supporting unit  40 . On the other hand, a bolt  25  is provided near to the supporting unit  40  on the turntable  22 . In this embodiment, the tilting guide  42  and the bolt  25  are provided on the supporting unit  40  for restricting the inclination range of the supporting unit  40  with respect to the turntable  22 . When the supporting unit  40  is tilted with respect to the turntable  22 , the tilting guide  42  contacts a head of the bolt  25 . The bolt  25  and the tilting guide  42  restrict the supporting unit  40  from tilting past a predetermined angle range.  
         [0045]     Next, the base unit  20  will be described in greater detail. The base unit  20  also includes a rotation supporting unit  26 , a handle  27 , and a lock lever  28 . The rotation supporting unit  26  is provided on the base  21  and supports the turntable  22  so the turntable  22  can rotate with respect to the base  21 . The rotation supporting unit  26  has a plurality of recesses  26   a , as shown in  FIG. 3 , formed on the bottom side thereof. The plurality of recesses  26   a  are arranged at predetermined intervals such as 7.5°.  
         [0046]     In this embodiment, the recesses  26   a  are formed at 7.5° intervals, i.e., 0°, 7.5°, 15°, 22.5°, 30°, 37.5°, and 45°. The recesses are given the corresponding label indicating of the angle from 0° such as 0°, 7.5°, 15°, 22.5°, 30°, 37.5°, and 45°, respectively.  
         [0047]     However, the recess  26   a  is not always formed at the angle position which is the exactly same as the labeled angle position from 0° due to the manufacture errors. In other words, even if the recess  26   a  is labeled 30°, the recess  26   a  labeled 30° is not always positioned at an exactly 30° angle from 0° due to the manufacture errors and manufacturing accuracy, for example. Accordingly, even if the recess  26   a  labeled 30° may be provided at any different angle position from the exact 30° position such as 29.5° or 30.5°, this recess is referred as the recess labeled 30° and considered to be positioned at 30° angle from 0°, as long as the recess is labeled 30°. The same thing applies to other recesses labeled the angle. The above angle position of the recess is referred to a predetermined nominal position in the present invention.  
         [0048]     The handle  27  is used for rotating the turntable  22  with respect to the base  21 . The lock lever  28  is provided on the turntable  22  and includes an engaging unit  29  for engaging with one of the plurality of recesses  26   a  (see  FIG. 3 ). A limit switch LS 1  is provided below the turntable  22  and above the lock lever  28 . When pressed downward, the lock lever  28  disengages the engaging unit  29  from the recess  26   a , enabling the turntable  22  to rotate. The limit switch LS 1  is turned on when the lock lever  28  is engaged in one of the recesses  26   a . And the limit switch LS 1  is turned off when the lock lever  28  is not engaged in the recess  26   a.    
         [0049]     A display  70  is provided on the front surface (the right side in  FIG. 1 ) of the turntable  22  for displaying the rotation angle of the turntable  22  from a reference position and the inclination angle of the supporting unit  40  with respect to the top surface of the base unit  20 . In this embodiment, the reference position is defined as the origin point for measuring an angle of inclination and/or rotation of a movable member such as the turntable  22  and the supporting unit  40  with respect to the base  21 . For example, if the movable member is the turntable  22 , the reference position is generally the position at which the side faces of the cutter blade  31  is positioned perpendicularly to the contact surface  23   a  of the fence  23 . If the movable member is the supporting unit  40 , the reference position is a vertical direction which is a substantially parallel to the normal to the top surface of the turntable  22 .  
         [0050]     Next, the display  70  will be described in greater detail with reference to  FIG. 2 .  
         [0051]      FIG. 2  shows a controller  100  for controlling the display  70 . The controller  100  includes a battery  110 , a constant voltage circuit  120 , a rotation position sensor  130 , an inclination position sensor  140 , a display reset unit  150 , a microcomputer  160 , a memory  170 , an inclination angle sensor  180 , and a rotation angle sensor  190 .  
         [0052]     The constant voltage circuit  120  includes a 3-terminal regulator  121 , switching elements S 1  and S 2 , a reset IC  122 , a switch S 3 , diodes D 1  and D 2 , resistors R 1 -R 3 , and capacitors C 1  and C 2 . When the switching element S 1  is turned on, the 3-terminal regulator  121  outputs power supplied from the battery  110  at a constant voltage Vcc.  
         [0053]     The on/off status of the switching element S 1  is switched according to the on/off status of the switch S 3  and the switching element S 2 . In other words, when the switching element S 1  is off, if the user switches the switch S 3  on and the output voltage from the battery  110  exceeds a predetermined value, the switching element S 1  is turned on by the reset IC  122  and the switching element S 2 . Accordingly, power is supplied from the constant voltage circuit  120  to the microcomputer  160 . At the same time, the microcomputer  160  outputs a signal for continuing the power supply.  
         [0054]     On the other hand, when the switch S 3  is switched on while the switching element S 1  is on, the microcomputer  160  responds by outputting a signal for turning off the switching element S 1 , terminating the power supply to the microcomputer  160 .  
         [0055]     The rotation position sensor  130  includes a resistor R 4  and a limit switch LS 1 . The rotation position sensor  130  detects whether the turntable  22  is in any one of the plurality of recesses  26   a . In other words, the rotation position sensor  20  detects that the turntable  22  is engaged in one of the recesses  26   a . In this embodiment, each of the recesses  26   a  is formed in 7.5° increments from the reference position. Generally, the initial reference position is the position in order that the side surface of the cutter blade  31  will be positioned at a right angle with respect to the contact surface  23   a  of the fence  23 .  
         [0056]     The inclination position sensor  140  includes resistors R 5  and R 6 , and limit switches LS 2  and LS 3 . The inclination position sensor  140  detects whether the side surfaces of the cutter blade  31  are at a predetermined angular position with respect to the top surface of the base  21 . In other words, the inclination position sensor  140  detects whether the tilting guide  42  and bolts  25  are tilted as far as a maximum inclination angle.  
         [0057]     The display reset unit  150  includes resistors R 7  and R 8 , and limit switches LS 4  and LS 5 . The display reset unit  150  functions for resetting the displayed inclination and/or rotation angles to zero. According to the display reset unit  150 , the user can select any angular position as the reference position for measuring an angle to the desired position. Therefore, the display  70  displays an angle to any angular position from the reference position which the user selects.  
         [0058]     The microcomputer  160  includes a CPU  161 , a ROM  162 , a RAM  163 , a timer  164 , an A/D converter  165 , output ports  166   a ,  166   b , and  166   c , a reset input port  167 , and memory ports  168   a  and  168   b . The microcomputer  160  uses the timer  164  to receive signals from the inclination angle sensor  180  and rotation angle sensor  190  via the A/D converter  165  at fixed intervals; to receive signals from the rotation position sensor  130 , inclination position sensor  140 , and display reset unit  150  via the input port  168   a ; and to receive a signal from the memory  170  via the input port  168   b . The microcomputer  160  calculates the inclination and rotation angles based on the signals from the sensors  130 ,  140 ,  150 ,  180 , and  190  to output the calculated angles to the display  70  via the output port  166   c . The microcomputer  160  also outputs a signal for turning off the switching element S 1  in response to an output signal from the reset IC  122  to control the power supply from the battery  110 . The microcomputer  160  also outputs the calculated results for the inclination and rotation angles to the memory  170 .  
         [0059]     The memory  170  is configured of an EEPROM, for example, and functions to store the inclination angle and rotation angle outputted from the microcomputer  160  and the corresponding output value of the inclination and rotation angle sensors  180  and  190 . In addition, the memory  170  stores the table including the relationship between each of the recesses  26   a  and the corresponding signal value from the inclination and rotation angle sensors  180  and  190 . The memory renews the table in response to the output of the microcomputer  160 .  
         [0060]     A reset IC  123  is provided between the output terminal of the 3-terminal regulator  121  and the microcomputer  160  to transmit a low level reset signal to the microcomputer  160  via the reset input port  167  depending on an output voltage from the 3-terminal regulator  121  to reset the microcomputer  160 .  
         [0061]     The inclination angle sensor  180  includes a resistor R 9  and the potentiometer  60 . The potentiometer  60  is provided for detecting the amount of inclination of the supporting unit  40  from the vertical direction, which is substantially perpendicular to the top surface of the turntable  22 .  
         [0062]     The rotation angle sensor  190  includes a resistor R 10  and the potentiometer  50 . The potentiometer  50  is provided for detecting the amount of rotation of the turntable  22  with respect to the base  21 . In this embodiment, the potentiometer  50  detects the rotational amount of the turntable  22  from the reference position.  
         [0063]     Since the resistance values of the potentiometer  60  and the potentiometer  50  change linearly in synchronization with angular increments, the voltages outputted from the potentiometer  60  and potentiometer  50  change linearly depending on the angle increments.  
         [0064]     Further, when the support unit  40  is positioned at one of the plurality of predetermined inclination angles or rotation angles, the memory  170  stores a table showing correspondences between voltages outputted from the potentiometer  60  and potentiometer  50  and each of the plurality of predetermined inclination angles and rotation angles. In this embodiment, the plurality of recesses  26   a  are formed on the base  21  side at 7.5° intervals. Each of the recesses  26   a  corresponds to one of predetermined rotation angles. The predetermined inclination angles refer to 0°, 15°, 30°, and 45°, which are defined by the supporting unit  40  and the normal to the top surface of the turntable  22 .  
         [0065]     The display  70  is configured of a liquid crystal display, for example, and functions to display the inclination angle and rotation angle which is computed by the microcomputer  160 .  
         [0066]     Next, inclination states of the miter saw  10  will be described with reference to  FIGS. 3 and 4 .  
         [0067]     In  FIG. 3 , the supporting unit  40  is positioned at a right angle to the top surface of the base  21 , and the side surfaces of the cutter blade  31  are likewise oriented at right angles to the top surface of the base  21 . In this embodiment, the above orientation of the supporting unit  40  corresponds to the reference position. In  FIG. 4 , the supporting unit  40  is positioned at its maximum inclination angle from the reference position, so that the side surfaces of the cutter blade  31  form an angle of 45° from the normal direction to the top surface of the base  21 .  
         [0068]     As shown in  FIGS. 3 and 4 , feet  21   a  are attached to the bottom of the base  21 . And the plurality of recesses  26   a  are formed in the rotation supporting unit  26  to correspond to a plurality of predetermined angles. The engaging unit  29  is retained in one of the plurality of recesses  26   a . The bolts  25  prevent the side surfaces of the cutter blade  31  from inclining past 45° from the reference position, that is, the vertical direction in this embodiment. Specifically, the bolts  25  can engage with the tilting guide  42  of the supporting unit  40  for restricting the amount that the supporting unit  40  inclines. As shown in  FIG. 3 , the tilting guide  42   b  and the bolt  25   b  on one side contact with each other when the side surfaces of the cutter blade  31  are oriented at a right angle from the vertical reference direction Z. As shown in  FIG. 4 , the tilting guide  42   a  and the bolt  25   a  on the other side contact with one another when the supporting unit  40  is positioned at the maximum inclination angle from the vertical reference direction Z such that the side surfaces of the cutter blade  31  form an angle of 45° with the top surface of the turntable  22 .  
         [0069]     As shown in  FIGS. 3 and 4 , the limit switches LS 2  and LS 3  are provided on the turntable  22  near the bolts  25  and protrude slightly above the heads of the bolts  25  for detecting the maximum inclination position. The limit switches LS 2  is turned on by the tilting guide  42   a  when the tilting guide  42   a  contacts with the corresponding bolt  25   a , as shown in  FIG. 4 . The limit switches LS 3  is turned on by the tilting guide  42   b  when the tilting guide  42   b  contacts with the corresponding bolt  25   b  as shown in  FIG. 3 . Specifically, the limit switch LS 3  turns on when the supporting unit is at the vertical reference position shown in  FIG. 3 . And the limit switch LS 2  turns on when the support unit  40  is at the maximum inclination position 45° shown in  FIG. 4 .  
         [0070]     Next, rotation states of the turntable  22  in the miter saw  10  of this embodiment will be described with reference to  FIGS. 5 and 6 .  
         [0071]      FIG. 5  shows the engaging unit  29  of the lock lever  28  engaged with one of the recesses  26   a  formed in the base  21 .  FIG. 6  shows the engaging unit  29  is disengaged from the recess  26   a  by pressing the lock lever  28  downward.  
         [0072]     As shown in  FIGS. 5 and 6 , the limit switch LS 1  is provided on the bottom surface near the front end of the turntable  22  (the right side in the drawing) and protrudes downward. As shown in  FIG. 5 , the limit switch LS 1  is on when the lock lever  28  is positioned upward through its own elastic force and the engaging unit  29  provided integrally on the lock lever  28  is engaged with one of the plurality of recesses  26   a  formed in the rotation supporting unit  26  of the base  21  (see  FIGS. 3 and 4 ). The limit switch LS 1  is configured to turn off when the engaging unit  29  disengages from the recess  26   a  as the lock lever  28  is pushed downward, as shown in  FIG. 6 . In this embodiment, the limit switch LS 1  is turned off when the lock lever  28  is not in any one of the recesses  26   a . For example, this condition means that the turntable  22  is out of the predetermined position of the base  21 .  
         [0073]     The recesses  26   a  are formed at intervals of 7.5° in the rotational direction of the turntable  22 , for example. Rotation of the turntable  22  is not allowed when the engaging unit  29  is engaged in one of the recesses  26   a . In this embodiment, the turntable  22  can easily be fixed at the relatively commonly used rotation angles of 15°, 30°, and 45° from the reference position.  
         [0074]     To rotate the turntable  22  with respect to the base  21 , the user grips the handle  27  and, with the same hand, pushes down the lock lever  28  to disengage the engaging unit  29  from the recess  26   a , as shown in  FIG. 6 . In this state, the user can move the handle  27  to rotate the turntable  22  to a desired position with respect to the base  21 .  
         [0075]     Owing to the force of gravity, the turntable  22  does not easily rotate with respect to the base  21 , even when the engaging unit  29  is not engaged in one of the recesses  26   a . Therefore, cutting operations can still be performed when the engaging unit  29  and recess  26   a  are not engaged. However, another mechanism for fixing the turntable  22  with respect to the base  21  can be provided for performing cutting operations on a workpiece when the engaging unit  29  is not engaged in one of the recesses  26   a.    
         [0076]     Next, the process for displaying the inclination angle and rotation angle of the miter saw  10  will be described with reference to  FIG. 7 .  
         [0077]     When the user switches on the switch S 3 , the reset IC  122  turns on the switching element S 1  after the voltage of the battery  110  exceeds a first predetermined value. A predetermined fixed voltage is applied to the microcomputer  160 . The microcomputer  160  then outputs a signal for continuing the power supply from the output port  166   b , thereby maintaining the on state of the switching element S 1  and enabling the display  70  to display (S 101 ).  
         [0078]     Next, the microcomputer  160  outputs a signal via the output port  166   c  for displaying a demo screen on the display  70  (S 102 ). Possible examples of this demo screen are the model name of the miter saw or a greeting. This screen can enhance the user&#39;s fondness for the miter saw  10 . It should be noted that the demo screen may be skipped depending on the application of the miter saw  10 . Simultaneously, the microcomputer  160  starts the timer  164  (S 103 ).  
         [0079]     After the demo screen is displayed in S 102 , the microcomputer  160  determines whether a predetermined time t 1  has elapsed after the timer  164  began counting (S 103 ). If the time t 1  has not elapsed, then the display of the demo screen is maintained on the display  70  (S 104 :NO). When it is determined in S 104  that the time t 1  has elapsed (S 104 :YES), the microcomputer  160  starts a sampling timer for detecting angular display data (Slo 5 ). Next, the microcomputer  160  determines whether a time t 2  has elapsed after the sampling timer was started (S 106 ). If the microcomputer  160  determines that the time t 2  has elapsed (S 106 :YES), then the sampling timer is reset and restarted (S 107 ). However, if the microcomputer  160  determines in S 106  that the time t 2  has not elapsed, then the process loops back to S 106  until the time t 2  has elapsed.  
         [0080]     Next, the microcomputer  160  detects signal output from the reset IC  122  with the input port  166   a  and determines whether the user has operated the switch S 3  for turning off the display  70  (S 108 ). If the switch S 3  has been operated, a high signal is inputted into the input port  166   a . Accordingly, the microcomputer  160  determines that the user operated the switch S 3  to turn off the display  70  (S 108 : YES), and the microcomputer  160  outputs a signal via the output port  166   c  for turning off the display  70 . At the same time, the microcomputer  160  outputs a signal via the output port  166   b  for halting power supply to the microcomputer  160 , thereby turning off the switching element S 1  (S 109 ).  
         [0081]     If a low signal has been inputted into the input port  166   a  in S 108 , then the microcomputer  160  determines that the user has not operated the switch S 3  for turning off the display  70 . Then, the microcomputer  160  advances to a rotation angle display procedure (S 110 ) and an inclination angle display procedure (S 111 ) sequentially. If the microcomputer  160  determines that the switch S 3  is off (S 108 :NO), the microcomputer  160  advances to the rotation angle display procedure (S 110 ). The rotation angle display procedure (S 110 ) is to calculate and display a rotational amount of the turntable  22  from the reference position, that is, an angle from the reference position to the actual angular position of the turntable  22  with respect to the base  21 . The inclination angle display procedure (S 111 ) is to calculate and display a tilting amount of the supporting unit  40  from the vertical reference position, that is, an angle from the vertical reference position to the inclined turntable  22 .  
         [0082]     The details of the rotation angle display procedure will be described referring to  FIG. 8 . Referring to  FIG. 8 , the microcomputer  160  receives voltage data from the rotation angle sensor  190  based on output from the potentiometer  50  through the A/D converter  165  (S 201 ).  
         [0083]     Next, voltage data of the rotation angle sensor  190  corresponding to the recesses  26   a  is read from the memory  170  (S 202 ). An output from the rotation position sensor  130  is read via the input port  168   a  for determining whether the limit switch LS 1  has been turned on. In other words, the microcomputer  160  determines whether the engaging unit  29  is retained in one of the recesses  26   a  based on the output from the rotation position sensor  130  (S 203 ).  
         [0084]     Here, the predetermined angular data corresponding to the recesses  26   a  stored in the memory  170  is output voltage of the rotation angle sensor  190  for 7.5°, 15°, 22.5°, . . . , respectively.  
         [0085]     The microcomputer  160  determines that the engaging unit  29  is not retained in any of the recesses  26   a  when the limit switch LS 1  is not on in S 203  (S 203 :NO). Therefore, the microcomputer  160  uses correspondences between output voltage values from the rotation angle sensor  190  and predetermined rotation angles such as 7.5°, 15°, 22.5°, . . . , stored in the memory  170 , and then calculates the rotation angle based on a voltage value outputted from the rotation angle sensor  190 . The microcomputer  160  displays this rotation angle, i.e., rotation amount on the display  70 .  
         [0086]     The above calculation of the rotation angle will be described in detail. To calculate the rotation angle, the microcomputer  160  compares various voltage data in the memory  170  to the output voltage from the rotation angle sensor  190  and selects two predetermined positions from the memory  170  (S 204 ). The predetermined positions satisfy the following conditions. One of them is a first set of a voltage value which is smaller than and the closest to the output voltage of the rotation angle sensor  190  and the corresponding first angular position. The other of them is a second set of a voltage which is more than and the closest to the output voltage of the rotation angle sensor  190  and the corresponding second angular position. The microcomputer  160  then uses a linear approximation method with the two sets of data to calculate the rotational amount of the turntable  22  (S 205 ) It should be noted that the microprocessor  160  can use any type of approximation method to obtain the rotational amount of the turntable  22  in addition to the linear approximation method. The microcomputer  160  then sends the data indicating of the calculated rotation amount of the turntable  22  to the display  70  (S 206 ). The microcomputer  160  then advances to S 111 .  
         [0087]     However, the microcomputer  160  determines that the engaging unit  29  is retained in one of the recesses  26   a  corresponding to a predetermined rotation angle when the limit switch LS 1  is on in S 203 . The microcomputer  160  then selects the predetermined rotation angle among the data read from the memory  170 , and displays the selected rotation angle on the display  70  (S 208 ).  
         [0088]     To calculate the rotation angle in this case, the microcomputer  160  compares various voltage data in the memory  170  to the output voltage from the rotation angle sensor  190 . The microcomputer  160  selects the predetermined angular data from the memory  170  that is the nearest to the output voltage from the rotation angle sensor  190  and displays the angle of this predetermined angular data as the rotation angle (S 208 ).  
         [0089]     After completing the process in S 208 , the microcomputer  160  sends the output voltage from the rotation angle sensor  190  and the corresponding predetermined position in the memory  170  via the output port  166   a  (S 209 ). In other words, the microprocessor  160  renews the table including the correspondence between the predetermined positions and the corresponding output voltage data of the rotation angle sensor  190  (S 209 ). The microprocessor  160  then advances to Sill (See  FIG. 7 ).  
         [0090]     Next, the inclination angle display procedure will be described in detail referring to  FIG. 9 . In this procedure, the microcomputer  160  calculates and displays the inclination angle of the miter saw  10 . The microcomputer  160  receives voltage data from the inclination angle sensor  180  (S 301 ).  
         [0091]     Next, the microcomputer  160  reads inclination angle data from the memory  170  corresponding to the positions at which the limit switches LS 2  and LS 3  are on when the tilting guide  42  and bolt  25  are engaged (S 302 ). Output from the inclination position sensor  140  indicating whether the limit switches LS 2  and LS 3  are on is inputted via the input port  166   a . The microcomputer  160  determines whether the tilting guide  42  is engaged with the bolt  25  and either the limit switch LS 2  or limit switch LS 3  is on (S 303 ).  
         [0092]     When neither the limit switch LS 2  nor limit switch LS 3  is on in S 216 , the microcomputer  160  determines that the tilting guide  42  and bolt  25  are not engaged. The microcomputer  160  uses the table of corresponding voltages and inclination angles stored in the memory  170  and the voltages outputted from the inclination angle sensor  180  to calculate the inclination angle of the supporting unit (S 304 ) and displays this inclination angle on the display  70  (S 305 ). The microprocessor  160  then advances to S  112 .  
         [0093]     In S 304 , the microcomputer  160  compares a plurality of voltage data stored in the memory  170  to the output voltage from the inclination angle sensor  180  to select two values from the plurality of voltages stored in the memory  170 , including one slightly larger than and the closest to the output voltage and the other slightly smaller than and the closest to the output voltage. Using a linear approximation between the angles corresponding to the two selected voltages, the microcomputer  160  calculates the inclination angle equivalent to the voltage output from the inclination angle sensor  180  (S 304 ) and displays the calculated inclination angle as the inclination angle of the supporting unit  40  (S 305 ).  
         [0094]     When either the limit switch LS 2  or the limit switch LS 3  is on in S 303 , the microcomputer  160  determines that the tilting guide  42  and bolt  25  are engaged. The microcomputer  160  references the memory  170  to find the inclination angle corresponding to the voltage outputted from the inclination angle sensor  180  (S 306 ) and displays this inclination angle on the display  70  (S 307 ).  
         [0095]     To calculate the inclination angle in this case, the microcomputer  160  compares various voltage data stored in the memory  170  to the voltage outputted from the inclination angle sensor  180 . The microcomputer  160  selects an inclination angle exhibiting the nearest voltage to the voltage outputted from the inclination angle sensor  180  from the data stored in the memory  170  (S 306 ) and displays this inclination angle (S 307 ).  
         [0096]     After completing S 307 , the microcomputer  160  sends the inclination angle corresponding to output from the inclination angle sensor  180  to the memory  170  via the output port  168   a  to renew the table in the memory  170  (S 308 ). The microcomputer  160  then advances to S  112 .  
         [0097]     Next, the microcomputer  160  checks output from the display reset unit  150  via the input port  166   a  to determine whether the limit switch LS 5  for resetting the displayed rotation angle is on (S 112 ). The microcomputer  160  jumps to S 116  if the limit switch LS 5  is not on. However, if the limit switch LS 5  is on, the microcomputer  160  resets the displayed rotation angle to 0° via the output port  166   c  (S 113 ) and switches the reference position to another reference position corresponding to the displayed rotation angle (S 114 ). The microcomputer  160  calculates a new predetermined angle corresponding to the recess  26   a  based on the rotation angle at the point of reset and stores this new angle in the memory  170  (S 115 )  
         [0098]     Next, the microcomputer  160  determines whether the limit switch LS 4  for resetting the displayed inclination angle has been turned on (S 116 ). The microcomputer  160  jumps to S 120  if the limit switch LS 4  is not on. However, if the limit switch LS 4  is on, the microcomputer  160  resets the displayed inclination angle to zero (S 117 ) and switches the vertical reference position to another reference position corresponding to the angle displayed on the display  70  when the limit switch LS 4  is on (S 118 ). The microcomputer  160  calculates a new inclination angle corresponding to the position at which the tilting guide  42  and bolt  25  engage based on the inclination angle at the point of reset and stores this new value in the memory  170  (S 119 ).  
         [0099]     In S 115  and S 119 , the memory  170  is allocated a different area from the initial area for storing data which is sent from the microcomputer  160 , after the display reset unit  150  is activated by pressing the limit switches LS 4  or LS 5 . Accordingly, the memory  170  can store two different kinds of table including the correspondence between the predetermined position and the voltage data of the rotation and inclination angle sensors  180  and  190 , after at least one of the limit switches LS 4  and LS 5  is turned on.  
         [0100]     The memory  170  can continue storing the two tables, the initial one and the new table made by resetting the display  70 , after the power supply to the microcomputer  160  is turned off. Therefore, this adds a new convenience in which the microcomputer  160  can utilize the two tables depending on the user&#39;s preference after the power is turned off and turned back on again. It is also possible to provide another switch for recovering the initial table for the calculation of angle without deleting the new table stored in the memory  170 , when the power is turned off and turned back on after the display reset unit  150  is activated. With this configuration, the present invention can provide an angle displaying device suited to the customer&#39;s needs.  
         [0101]     After completing the display reset process, the computer  160  determines whether the signal output from the rotation angle sensor  190  remains the same for at least a predetermined time period (S 120 ). If any changes occur during the predetermined time period, the microcomputer  160  returns to S 106 .  
         [0102]     However, if the signal outputted from the rotation angle sensor  190  remains the same for the predetermined time period in S 120 , then the microcomputer  160  determines whether the signal outputted from the inclination angle sensor  180  remains the same for a predetermined time period (S 121 ). If the signal changes during this time period, then the microcomputer  160  returns to S 106 .  
         [0103]     However, if there are no changes over the predetermined time period in S 121 , then in S 109  the microcomputer  160  outputs a signal for turning off the display  70  via the output port  166   c . At the same time, the microcomputer  160  outputs a signal for halting power supply to the microcomputer  160  via the output port  166   b.    
         [0104]     In this way, the microcomputer  160  jumps to S 109  if there are no changes during the predetermined time periods, outputs a signal via the output port  166   c  for turning off the display  70 , and outputs a signal via the output port  166   b  for halting power supply to the microcomputer  160 . With this construction, the miter saw  10  can reduce energy consumption of the battery  110 , which is the power source for the angle displaying device  70 .  
         [0105]     While the miter saw  10  in this embodiment described above has an inclination function for the supporting unit  40  and a rotation function for the turntable  22 , the miter saw  10  may also be provided with only one of these functions.  
         [0106]     The angle sensor in this embodiment is configured of the potentiometers  50  and  60 , but is not limited to such devices. For example, a rotary encoder for counting the angle of rotation may be used as the angle sensor. Next, a process for detecting the rotation angle of the turntable  22  using a rotary encoder will be described.  
         [0107]     When using a rotary encoder to detect rotations of the turntable  22 , twenty pulses are generated during each 1° that the turntable  22  rotates for two types of pulses A and B that are 90° out of phase from each other. These pulses are used to detect the rotation angle of the turntable  22 . Using the two types of pulses A and B that are 90° out of phase, it is possible to detect whether the turntable  22  is rotating clockwise or counterclockwise.  
         [0108]     The following is a specific example shown in  FIG. 10 , where “1” indicates a high pulse and “0” a low pulse. If pulse A is 0 and pulse B is 0 and subsequently pulse A becomes 1 while pulse B remains 0, then it can be determined that the turntable  22  is rotating to the right in  FIG. 10 , that is, clockwise. However, if pulses A and B are 0 and subsequently pulse B becomes 1 while pulse A remains 0, then it can be determined that the turntable  22  is rotating to the left in  FIG. 10 , that is, counterclockwise.  
         [0109]     Further, twenty pulses are generated for each type A and B while the turntable  22  rotates 1°. Hence, one pulse for each type A and B is generated each time the turntable  22  rotates 0.05°, as shown in  FIG. 10 . If for example the turntable  22  rotates from a position of 0° to a position of 45°, 90° pulses are generated for each type A and B.  
         [0110]     The microcomputer  160  displays the rotation angle of the turntable  22  in units of 0.2°. In other words, the rotation angle of the turntable  22  displayed on the display  70  is updated to a value larger or smaller by 0.2° each time the turntable  22  rotates 0.2° clockwise or counterclockwise.  
         [0111]     At this time, we will assume that 0° is displayed on the display  70  and that the rotation angle of the turntable  22  is also exactly 0°. As the turntable  22  rotates to the right in  FIG. 10 , the rotation angle displayed on the display  70  remains at 0° even when the microcomputer  160  detects the pulse indicating that the turntable  22  has rotated to the 0.05° position. As the turntable  22  continues to rotate and the microcomputer  160  detects a pulse indicating that the turntable  22  has rotated to the 0.20° position, the microcomputer  160  adds 0.2° to the value displayed on the display  70  and updates the display to 0.2°. As the turntable  22  continues to rotate and the microcomputer  160  detects a pulse indicating that the turntable  22  has rotated to the 0.30° position, the microcomputer  160  adds 0.2° to the display on the display  70  and updates the display to 0.4°.  
         [0112]     In contrast, let us assume that 0.4° is displayed on the display  70  and that the turntable  22  is rotating in the counterclockwise direction from a rotation angle of exactly 0.4°. Here, the rotation angle displayed on the display  70  remains at 0.4° even when the microcomputer  160  detects a pulse indicating that the turntable  22  has rotated to the 0.35° position. As the turntable  22  continues to rotate counterclockwise and the microcomputer  160  detects a pulse indicating that the turntable  22  has rotated to 0.30°, the microcomputer  160  subtracts 0.20 from the value displayed on the display  70  and updates the display  70  to 0.20. As the turntable  22  continues to rotate and the microcomputer  160  detects a pulse indicating that the turntable  22  has rotated to 0.20°, the microcomputer  160  again subtracts 0.20 from the value displayed on the display  70  and updates the display  70  to 0°.  
         [0113]     Next, let us assume that 14.8° is displayed on the display  70  and that the rotation angle of the turntable  22  is exactly 14.80. The turntable  22  is rotating clockwise, that is, to the right in  FIG. 11 . When the microcomputer  160  detects a pulse indicating that the turntable  22  has rotated to the 14.85° position, the microcomputer  160  displays a special rotation angle of 15.0° on the display  70 .  
         [0114]     As the turntable  22  continues to rotate from this state and the microcomputer  160  detects a pulse indicating that the turntable  22  has rotated to 15.15°, the microcomputer  160  displays 15.2° on the display  70 .  
         [0115]     In contrast, let us assume that 15.2° is displayed on the display  70  and that the rotation angle of the turntable  22  is exactly 15.20. Here, the turntable  22  is rotating counterclockwise, that is, toward the left in  FIG. 11 . When the microcomputer  160  detects a pulse indicating that the turntable  22  has rotated to the 15.15° position, the microcomputer  160  displays the special rotation angle of 15.0° on the display  70 .  
         [0116]     As the turntable  22  continues to rotate from this position and the microcomputer  160  detects a pulse indicating that the turntable  22  has rotated to 14.85°, the microcomputer  160  displays 14.8° on the display  70 .  
         [0117]     Now let us assume that 22.4° is displayed on the display  70 , but the rotation angle of the turntable  22  is 22.35°. The turntable  22  is rotating clockwise, that is, toward the right in  FIG. 12 . When the microcomputer  160  detects a pulse indicating that the turntable  22  has rotated to the 22.40° position, the microcomputer  160  displays a special rotation angle of 22.5° on the display  70 .  
         [0118]     As the turntable  22  continues to rotate from this position and the microcomputer  160  detects a pulse indicating that the turntable  22  has rotated to 22.60°, the microcomputer  160  displays 22.6° on the display  70 .  
         [0119]     In contrast, let us assume that 22.6° is displayed on the display  70  and the rotation angle of the turntable  22  is 22.65°, while the turntable  22  rotates counterclockwise, that is, toward the left in  FIG. 12 . When the microcomputer  160  detects a pulse indicating that the turntable  22  has rotated to the 22.60°, the microcomputer  160  displays the special rotation angle of 22.5° on the display  70 .  
         [0120]     As the turntable  22  continues to rotate from this position and the microcomputer  160  detects a pulse indicating that the turntable  22  has rotated to 22.40°, the microcomputer  160  displays 22.4° on the display  70 .  
         [0121]     Next, we will assume that 31.4° is displayed on the display  70  and the rotation angle of the turntable  22  is at 31.40°, where the turntable  22  rotates clockwise, that is, toward the right in  FIG. 13 . When the microcomputer  160  detects a pulse that indicates the turntable  22  has rotated to the 31.45° position, the microcomputer  160  displays a special rotation angle of 31.60 on the display  70 .  
         [0122]     As the turntable  22  continues to rotate from this position and the microcomputer  160  detects a pulse indicating that the turntable  22  has rotated to 31.75°, the microcomputer  160  displays 31.80 on the display  70 .  
         [0123]     In contrast, let us assume that 31.8° is displayed on the display  70  and the rotation angle of the turntable  22  is 31.80°, while the turntable  22  rotates counterclockwise, that is, toward the left in  FIG. 13 . When the microcomputer  160  detects a pulse indicating that the turntable  22  has rotated to the 31.75° position, the microcomputer  160  displays the special rotation angle of 31.6° on the display  70 .  
         [0124]     As the turntable  22  continues to rotate and the microcomputer  160  detects a pulse indicating that the turntable  22  has rotated to 31.45°, the microcomputer  160  displays 31.4° on the display  70 .  
         [0125]     Next, let us assume that 35.2° is displayed on the display  70  and the rotation angle of the turntable  22  is exactly 35.20°, as shown in  FIG. 14 . Here, the turntable  22  rotates clockwise, that is, toward the right in  FIG. 14 . When the microcomputer  160  detects a pulse indicating that the turntable  22  has rotated to the 35.25° position, the microcomputer  160  displays the special rotation angle of 35.3° on the display  70 .  
         [0126]     As the turntable  22  continues to rotate and the microcomputer  160  detects a pulse indicating that the turntable  22  has rotated to 35.35°, the microcomputer  160  displays 35.4° on the display  70 .  
         [0127]     In contrast, let us assume that 35.4°is displayed on the display  70  and that the rotation angle of the turntable  22  is exactly 35.40°. Here, the turntable  22  rotates counterclockwise, that is, toward the left in  FIG. 14 . When the microcomputer  160  detects a pulse indicating that the turntable  22  has rotated to the 35.35° position, the microcomputer  160  displays the special rotation angle of 35.3° on the display  70 .  
         [0128]     As the turntable  22  continues to rotate and the microcomputer  160  detects a pulse indicating that the turntable  22  has rotated to 35.25°, the microcomputer  160  displays 35.2° on the display  70 .  
         [0129]     Next, let us assume that 44.8° is displayed on the display  70  and that the rotation angle of the turntable  22  is 44.80°. Here, the turntable  22  rotates clockwise, that is, toward the right in  FIG. 15 . When the microcomputer  160  detects a pulse indicating that the turntable  22  has rotated to the 44.85° position, the microcomputer  160  displays a special rotation angle of 45.0° on the display  70 .  
         [0130]     As the turntable  22  continues to rotate and the microcomputer  160  detects a pulse indicating that the turntable  22  has rotated to 45.15°, the microcomputer  160  displays 45.2° on the display  70 .  
         [0131]     In contrast, let us assume that 45.2° is displayed on the display  70  and that the rotation angle of the turntable  22  is 45.20°. Here, the turntable  22  rotates counterclockwise, that is, toward the left in  FIG. 15 . When the microcomputer  160  detects a pulse indicating that the turntable  22  has rotated to the 45.15° position, the microcomputer  160  displays the special rotation angle of 45.0° on the display  70 .  
         [0132]     As the turntable  22  continues to rotate and the microcomputer  160  detects a pulse indicating that the turntable  22  has rotated to 44.85°, the microcomputer  160  displays 44.8° on the display  70 .  
         [0133]     With this method, when the pulse detected by the rotation angle sensor falls within the range of special rotation angles such as the proximity areas centering 0, 15, 22.5, 31.6, or 45, the microcomputer  160  can display the special rotation angle on the display  70 . Accordingly, the user can recognize when the turntable  22  has rotated to the predetermined rotation angle such as 0, 15, 22.5, 31.6, and 45. The inclination angle of the supporting unit  40  can similarly be detected using a rotary encoder.  
         [0134]     While in the embodiment described above the inclination function of the supporting unit  40  is capable of inclining only in one direction, the inclination function may be configured to incline both left and right using the right angle position as the reference point.  
         [0135]     In the embodiment described above, the tilting guide  42  and bolt  25  are configured to engage when the supporting unit  40  is in the right angle position or in the maximum inclination position. However, these engaging units may also be configured to engage at another position between the right angle position and the maximum inclination position. In such a case, it is preferable to provide a function for outputting a signal when the engaging units are engaged.  
         [0136]     In the embodiment described above, the miter saw  10  is provided with the turntable  22  that is capable of rotating over the base  21 , and the supporting unit  40  is coupled with the base  21  via the turntable  22 . However, the miter saw  10  may be configured without the turntable  22 , so that the supporting unit  40  couples directly with the base  21 .  
         [0137]     In the embodiment described above, the holder  32  is pivotably supported on the supporting unit  40 . However, the supporting unit  40  may be configured in a divided construction, wherein the portion supporting the pivoting axis  41  and holder  32  can slide over the portion coupled with the turntable  22  or the base  21  while remaining substantially parallel to the side surfaces of the cutter blade  31 .  
         [0138]     The miter saw  10  described above exhibits the following advantages.  
         [0139]     The miter saw  10  can display an angle without confusing a user.  
         [0140]     The miter saw  10  can cut the workpiece in an inclined direction with respect to the side face of the workpiece.  
         [0141]     The angle at which the supporting unit  40  or base  21  and the turntable  22  are engaged mechanically is displayed not based on a signal from the angle sensors  180  and  190 , but based on data in the table stored in the memory  170  for the predetermined angle. Accordingly, the angle displayed on the display matches with the angle indicated for each recess  26   a . Hence, the user is not provided with multiple data values that may cause confusion and lead to a decline in operability.  
         [0142]     When the supporting unit or base and the turntable are engaged mechanically at a predetermined angle, it is possible to correct the angle detected by the angle sensors and displayed on the display each time the supporting unit or base and the turntable are engaged mechanically at a predetermined angle. Hence, even when the angle detected by the angle sensors deviates from the angle determined through the mechanical engagement at a predetermined position, deviation in the displayed angle caused by detection errors can be suppressed.  
         [0143]     Positions are determined by engaging the tilting guide of the supporting unit with the bolt provided on the base or turntable when the side surfaces of the circular saw blade in relation to the top surface of the base are at a right angle (the most frequently used position) or at the maximum inclination (45°). Further, by providing the miter saw with an inclination angle sensor for outputting a signal to the controller when the side surfaces of the circular blade are at a right angle or at the maximum inclination angle with respect to the top surface of the base, it is possible to resolve discrepancies between the displayed angle and the angle determined by positioning for the most frequently used cutting positions.  
         [0144]     When the angle position set for engaging the tilting guide of the supporting unit with the head of a bolt differs from the angle detected by the inclination angle sensor when the engaging unit is engaged with the bolt head, it is possible to adjust the set angle position according to the detected angle. Hence, when a deviation is found with the set angle position, it is possible to adjust this position.  
         [0145]     The miter saw is configured to reset a displayed angle to zero at a desired position, in subsequent angle displaying operations, to display the inclination angle and rotation angle from the new reference position provided by resetting the displayed angle. With this construction, the user can set a desired position to 0°, the reference position, thereby improving operability.  
         [0146]     By resetting the displayed angle to zero, the memory can store the new table including the relationship between the recesses and the output from the sensors. Accordingly, the user can select one of the two tables showing the relationship from the memory after resetting the display to zero. Hence, the reference angle can easily be restored to the initial 0°, thereby improving operability.  
         [0147]     By providing the constant voltage power supply, it is possible to suppress a decline in detection accuracy.  
         [0148]     The display is positioned on the front surface of the turntable so that the user can look at the display easily during operations.  
         [0149]     If the displayed angle has not changed for more than the predetermined time period, the power supply is suspended. Accordingly, it is possible to reduce power consumption, which is particularly effective when the power source is a battery.  
         [0150]     When using a battery for the power source, the display can be installed at nearly any location without restriction. Using the power source for the cutting unit requires complex wiring, while a battery enables the display to be installed easily on the base or turntable, which improves readability of the displaying means.  
         [0151]     Displaying a demo unrelated to the angle display, such as the product&#39;s model name or a greeting, for a predetermined time after the power is first turned on can increase the user&#39;s feeling of affection toward the product.  
         [0152]     Configuring the turntable and base to engage at the 0° position, which is most frequently used, can improve operability.  
         [0153]     Providing a plurality of grooves at predetermined angular positions most frequently used can improve productivity. Further, it is possible to display angles without variations when detecting that the lever and groove are engaged, thereby preventing a decline in productivity.  
         [0154]     It is not necessary that the recesses  26   a  be formed at fixed intervals.  
         [0155]     Next, the following description will be made for explaining another embodiment of the miter saw  10 . In this embodiment, only the miter saw  10  has the different structure from that of the first embodiment described above. Accordingly, the explanation for the display  70  and the controller  100  will be omitted.  
         [0156]     As shown in  FIG. 16 , the miter saw  10  includes a base  301 , and a turntable  302  embedded in the center of the base  301  so that the top surface of the turntable  302  is flush with the top surface of the base  301 , as shown in  FIG. 16 , and capable of rotating within a horizontal plane. A workpiece P formed of wood is placed on the top surfaces of the base  301  and turntable  302 .  
         [0157]     As shown in  FIG. 17 , the base  301  includes side walls  301   a  and  301   b . A plurality of recesses  303  having arc shapes are formed in the inner side of the side wall  301   a . A stopper  304  is received in one of the recesses  303 . The stopper  304  is supported on a cover  305 , as shown in  FIG. 18 . The stopper  304  has a limit switch LS  10  provided on the tip thereof. The limit switch LS  10  is connected to the controller  100  (not shown). A stopper spring  306  urges the stopper  304  in a direction outward from the rotational center of the turntable  302  so that the stopper  304  is fitted into one of the recesses  303 . As shown in  FIGS. 18 and 19 , a handle  307  is twistingly fitted into the protruding end of the turntable  302  and is capable of pushing against the side wall  301   b  of the base  301  via a shaft  308  positioned at the end of the handle  307 . Rotation of the turntable  302  with respect to the base  301  is restricted by tightening the handle  307  to press the shaft  308  against the side wall  301   b.    
         [0158]     An operating member  310  is rotatably supported on the turntable  302  near the handle  307  by a lever shaft  309  that extends orthogonally to the axis of the handle  307 . The operating member  310  includes a lever part  310   a  that extends beneath the handle  307 . The user operates the lever part  310   a  using the same hand that grips the handle  307 .  
         [0159]     A protruding part  310   c  is formed on the operating member  310  substantially symmetrically opposite the lever part  310   a  with respect to the lever shaft  309 . An elongated hole  310   d  is formed through the protruding part  310   c  and is configured of a hole having a small diameter and a hole having a large diameter that are juxtaposed and in fluid communication. A pin  311  inserted in the hole  310   d  is maintained in the turntable  302  so as to be able to slide in the direction of its axis. The pin  311  includes a small diameter part  311   a  and a large diameter part  311   b . A spring  312  urges the pin  311  so that the small diameter part  311   a  is positioned in the protruding part  310   c  of the operating member  310  and supported therein, while at least an end portion of the large diameter part  311   b  protrudes outside the turntable  302 .  
         [0160]     A shaft  313  is also supported in the turntable  302  so as to be able to slide along its axis. One end of the shaft  313  is capable of contacting a protruding part  310   b  of the operating member  310 , while the other end contacts a protruding part  304   a  of the stopper  304 . When the operating member  310  is rotated, the stopper  304  is moved forward and backward via the shaft  313 .  
         [0161]     A fence  333  is fixed to the top surface of the base  301  for supporting the side surface of the workpiece P as shown in  FIG. 16 . A blade receiving plate (not shown) having a groove for inserting a saw blade  334  is fixed to the top center of the turntable  302 . When cutting the workpiece P, the saw blade  334  is inserted into the groove formed in this blade receiving plate so that the bottom edge of the saw blade  334  is lowered farther than the top surface of the turntable  302 . Thus, the blade receiving plate functions to prevent the saw blade  334  from producing a rough edge on the finished bottom surface of the workpiece P. A holder  315  is erected on the back edge of the turntable  302  via a holder shaft  314 . By positioning the axial center of the holder shaft  314  substantially flush with the top surface of the turntable  302 , the holder  315  can incline left and right about the top surface of the turntable  302  using the holder shaft  314  as a pivot point.  
         [0162]     As shown in  FIG. 20 , an elongated slot  302   a  is formed in the rear portion of the turntable  302  and centered over the holder shaft  314 . A clamp lever  316  penetrates the slot  302   a , while a screw part (not shown) formed on the end of the clamp lever  316  is screwed into a threaded hole formed in the back surface of the holder  315 . When the clamp lever  316  is loosened, the holder  315  can incline about the holder shaft  314  within the range of the slot  302   a . When the clamp lever  316  is tightened the turntable  302  is tightened between the clamp lever  316  and the holder  315  and the holder  315  is thus fixed at the desired position. The slot  302   a  is formed with a range sufficient to allow the holder  315  to incline about 45° both left and right.  
         [0163]     When the holder  315  is erected at a right angle to the turntable  302 , through-holes  315   a  formed at two locations through the top of the holder  315  run parallel to the top surface of the turntable  302 . Sliding member holding members (not shown) are provided in these through-holes  315   a , and two guide bars  317  extending parallel to each other in the left-to-right direction are inserted through the through-holes  315   a . The guide bars  317  are capable of sliding parallel to the top surface of the turntable  302  in the front-to-back direction via the sliding member holding members. A circular saw holder  318  is provided on the front end of the guide bars  317 , while a support  319  that prevents the guide bars  317  from coming out of the through-holes  315   a  is provided on the back end of the guide bars  317 . A knob  320  disposed on the side surface of the holder  315  restricts sliding of the guide bars  317 .  
         [0164]     A circular saw section  322  is pivotably supported on the top of the circular saw holder  318  via a shaft  321  and is capable of pivoting up and down over the top surface of the base  301 . A spring  323  is disposed between the circular saw holder  318  and the circular saw section  322  for urging the circular saw section  322  upward.  
         [0165]     The circular saw section  322  rotatably supports a blade shaft  324  for fixing the saw blade  334 . The circular saw section  322  is also configured of a motor unit  325  for generating a motive force that is coupled to the top of the blade shaft  324 , and a handle  326 .  
         [0166]     Stoppers  315   b  and  315   c  are provided on the front surface of the holder  315  for fixing the inclination position of the holder  315 . Stopper bolts  327  and  328  are screwed vertically into the top surface on the back of the turntable  302  at positions along the paths of the stoppers  315   b  and  315   c . When the holder  315  is inclined, the stopper  315   b  or stopper  315   c  engages with the head of the respective stopper bolt  327  or stopper bolt  328  at a predetermined inclination angle for setting the inclination position of the circular saw section  322 . The stopper bolt  327  is positioned to engage with the stopper  315   b  when the holder  315  is inclined to the left at 45°. The stopper bolt  328  is positioned to engage with the stopper  315   c  when the holder  315  is inclined to the right at 45°. A pin  329  is supported in the turntable  302  for fixing the position of the holder  315  at a right angle to the turntable  302  and is capable of moving horizontally in the front-to-back direction. When the holder  315  is positioned as shown in  FIG. 20 , a stopper bolt  330  screws horizontally into the holder  315  at a position along the path of the pin  329 . When the holder  315  is positioned for a right angle cut, the end of the stopper bolt  330  is in contact with the peripheral portion of the pin  329 .  
         [0167]     Next, the operations of the stopper devices used in the miter saw of the present invention will be described with reference to  FIGS. 17 and 18 .  
         [0168]     As shown in  FIGS. 17 and 18 , the stopper  304  is in a state of contact with the inner side of the side wall  1   a  by the urging force of the stopper spring  306 . When the turntable  302  is rotated, the stopper  304  becomes fitted into one of the recesses  303 , as shown in  FIG. 17 , preventing the turntable  302  from rotating farther. In addition, when the stopper  304  is engaged in one of the recesses  303 , the limit switch LS 10  on the tip of the stopper  304  is turned on so that the controller  100  can determine that the stopper  304  is engaged in the recess  303 . To rotate the turntable  302  farther, the user must pull the lever part  310   a  upward. Through this operation, the operating member  310  rotates, causing the protruding part  310   b  to push the shaft  313  toward the rotational center of the turntable  302 . The shaft  313  pushes against the protruding part  304   a  of the stopper  304  and the stopper  304  overcomes the urging force of the stopper spring  306  to be pushed out of the recess  303 , thereby releasing the restriction for rotating the turntable  302 . The turntable  302  can be rotated while this state is maintained.  
         [0169]     In order to again restrict rotation of the turntable  302 , the user releases the grip on the operating member  310 , allowing the stopper spring  306  to urge the stopper  304  back into one of the recesses  303 , thereby restricting rotation of the turntable  302 . Accordingly, it is necessary to pull up on the operating member  310  in order to rotate the turntable  302 .  
         [0170]     Next, operations to enable free rotation of the turntable  302  will be described. As shown in  FIG. 21 , the user lifts up on the lever part  310   a  and moves the pin  311  against the urging force of the spring  312  to insert the large diameter part  311   b  into the large diameter part of the hole  310   d . By releasing the operating member  310  in this state, the urging force of the stopper spring  306  causes the large diameter part  311   b  of the pin  311  to contact the inner walls of the hole  310   d . The frictional force of this contact restrains movement of the pin  311  so that the operating member  310  is engaged in its upwardly raised state (the position of the pin  311  being the engaging position). Since the stopper  304  is not inserted into the recesses  303  in this state, the stopper devices of the turntable  302  can be maintained in a released state, that is, an unlocked state.  
         [0171]     By increasing the frictional force between the outer surface of the large diameter part  311   b  and the inner surface of the hole  310   d  through a process for roughening one of the surfaces, this unlocked state can be more reliably maintained, thereby reducing the chance of the unlocked state being released suddenly.  
         [0172]     To fix the turntable  302  in a desired position of rotation, the handle  307  may be tightened to urge the side wall  301   b  via the shaft  308 .  
         [0173]     In order to once again engage the stopper device used to restrict rotations of the turntable  302 , that is, to release the unlocked state, the operating member  310  is temporarily pulled upward to create play between the pin  311  and the large diameter hole in the hole  310   d , enabling the pin  311  to be moved by the urging force of the spring  312  so that the small diameter part  311   a  becomes positioned in the hole  310   d  formed in the protruding part  310   c . Now, the operating member  310  can again rotate and the stopper device functions according to the normal operations described above (the pin  311  is positioned in the non-engaging position).  
         [0174]     While the invention has been described in detail with reference to specific embodiments thereof, it would be apparent to those skilled in the art that many modifications and variations may be made therein without departing from the spirit of the invention, the scope of which is defined by the attached claims.