Rotary hammer with rotation stop control trigger
United States Patent [191 Moores, Jr.  
 1 1 Apr. 8, 1975 1 1 ROTARY HAMMER WITH ROTATION STOP CONTROL TRIGGER [75] Inventor: Robert Gordon Moores, Jr.,  
 Cockeysville, Md.  
 [73] Assignee: The Black and Decker Manufacturing Company, Towson. Md.  
 [22] Filed: Feb. 7, 1974 [21] Appl. N0.: 440,293  
 Primary E.raminerJames A. Leppink Attorney, Agent, or Firm-Leonard Bloom; Edward D. Murphy; William Kovensky [57] ABSTRACT A rotary hammer having a rotation stop control trigger mounted adjacent to one end of a torque handle assembly. the torque taking handle assembly and the trigger being capable of being disposed in various positions on the housing of the rotary hammer. The rotation stop control trigger engages a driven clutch element which is keyed on an output shaft and is longitudinally slidable about the output shaft, the output shaft being in turn mounted so that its axis is parallel to the axis of rotation of the tool holder of the rotary hammer. The rotation stop control trigger is pivotally mounted in mounting means which also supports the torque taking handle, and the mounting means can be shifted to various selected fixed positions about the axis of the output shaft.  
 17 Claims, 4 Drawing Figures PATENTEDAPR 1915 3,876,014  
 SliEUlUFZ PATENTEDAPR 8l975 3,876,014  
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 ROTARY HAMMER WITH ROTATION STOP CONTROL TRIGGER FIELD OF THE INVENTION The present invention relates generally to rotary hammers, and more particularly to a rotary hammer of the type having a bit which can ,be rotated and impacted in one mode of operation and which can be declutched to prevent rotation in another mode of operation when the bit is only impacted.  
 BACKGROUND OF THE INVENTION In certain types of industrial applications it is desirable to provide a rotary hammer whose rotation can be stopped while providing only a hammering action. Thus, for example, when applying expansion anchors of the type shown in U.S. Pat. No. 2,918,290 to Werstein, it is desirable to both rotate and hammer the bit which carries the expansion anchor shell as it is being drilled into concrete or the like. When the expansion anchor shell has been inserted to the proper depth into the concrete, it is then desirable to Withdraw the expansion anchor, insert an expansion member in the form of a tapered plug into its leading end, and then to hammer the expansion anchor shell back into the concrete. During this final hammering the bit should not be rotated.  
  Prior to the development of the apparatus shown in this patent application, various alternative devices had been proposed for simultaneously impacting and rotating a bit or alternatively impacting the bit without rotating it. U.S. Pat. Nos. 3,370,655 to Chromy and 3,478,829 to Bixby both disclose attachments which were to be driven by a rotary hammer and which would support the expansion anchor. Each of these attach ments were provided with means to prevent rotation of the expansion anchor during one mode of operation. While these devices were satisfactory for the intended purpose, they were somewhat difficult to operate and also had the disadvantage of all attachments in that, not being an integral part of the tool, they were subject to being misplaced when needed. U.S. Pat. No. 3,430,708 to Miller discloses a rotary hammer which has internal clutching means which permit the rotary drive to the tool holder or bit to be declutched to prevent rotation of the bit when it is desirable to have the apparatus operate in only a hammering manner. This design had the disadvantage in that the mechanism which causes the drive to be interrupted bears against a constantly rotating member and therefore may have adverse wear characteristics. Furthermore, the mechanism by which the clutch was caused to be disengaged was awkwardly located and it was difficult for the operator of the rotary hammer to cause disengagement of the rotary drive means. U.S. Pat. No. 3,720,269 to Wanner, et al discloses a rotary hammer apparatus having a rotatable member which may be used to disengage the clutch&#39;to prevent the tool holder from rotating during certain modes of operation. The mechanism shown in this patent for disengaging the clutch is rather complex and furthermore, it is somewhat awkward for the operator of the rotary hammer to cause the rotatable member to be rotated to disengage the clutch. To this end, Wanner, et al discloses that the rotatable member may be inter-engaged with a torque receiving handle which would provide for disengagement of the clutch upon rotation of the handle. This has the disadvantage in that the handle may be inadvertently rotated while the operator is holding the rotary hammer causing disengagement of the clutch when a rotating drive is desired. Obviously it has the alternative disadvantage in that the handle may be rotated to cause the clutch to be engaged when it is desired to have only a hammering action. Furthermore, it should be noted that the handle shown in the Wanner, et al patent can only be disposed in a single position and cannot be disposed in varying positions to suit the convenience of the operator while still being utilized to cooperate with the rotatable member to cause a clutching action.  
 OBJECTS AND SUMMARY OF THE INVENTION It is an object of the present invention to provide a rotary hammer or the like of the type having a clutch to disengage the rotational drive to the bit of the rotary hammer wherein the clutch is operated by a trigger which is mounted adjacent to a torque receiving handle assembly.  
  It is a furtherobject of the present invention to provide a common mounting structure for a rotation stop control trigger and a torque receiving handle assembly for a rotary hammer or the like wherein the handle assembly and trigger may be disposed in various positions about the housing of the rotary hammer to suit the convenience of the operator.  
  It is a further object of the present invention to provide a trigger controlled clutch for a rotary hammer or the like wherein the portion of the trigger which engages a clutch part will not be subject to rubbing friction when the trigger is engaged to cause the clutch to be disengaged.  
  It is a further object of the present invention to provide a rotation stop control trigger for a rotary hammer or the like wherein the rotation stop control trigger does not bear against any rotating parts during normal operation when the tool holder of the rotary hammer is caused to be rotated.  
  It is a further object of the present invention to provide a rotary hammer or the like having a torque re ceiving handle assembly which is disposed adjacent to a rotation stop control trigger wherein the handle assembly may be changed to various positions without the employment of any external tools.  
  It is a further object of the present invention to provide a rotary hammer or the like having a clutch mechanism which disengages the rotary drive to a bit carried by the rotary hammer wherein a compact design is provided by mounting the clutch mechanism about a rotary output shaft which is disposed parallel to the axis of rotation of the tool holder.  
  These and other objects of the present invention are accomplished by providing a clutched drive to the bit of a rotary hammer wherein the drive, when engaged, causes the bit to rotate about its axis of rotation, the clutched drive including an output shaft having its axis of rotation parallel to the axis of rotation of the tool holder, a drive sleeve mounted about the output shaft, a driven sleeve keyed to the output shaft and rotatable wherewith, the driven sleeve being slidable about the output shaft between a first position wherein it is engaged with the driving sleeve and a second position where it is disengaged from the driving sleeve, the driven sleeve not rotating when it is in its second position, a trigger having a portion which extends into the housing and which engages the driven sleeve to move it away from the driving sleeve, the trigger being pivotally supported by mounting structure including a trigger housing disposed on the outside of the housing of the rotary hammer, the mounting structure also supporting a torque taking handle assembly which is threaded into one side of an annular member disposed about the driven shaft, the torque taking handle, trigger and trigger housing being disposable in various angular positions about the housing of the rotary hammer.  
 BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial sectional view through the rotary hammer of the present invention.  
  FIG. 2 is an enlarged view of a portion of the rotary hammer shown in FIG. 1, this Figure showing the clutch mechanism disposed in a disengaged position.  
  FIG. 3 is a section taken along the lines 3-3 of FIG. 1.  
  FIG. 4 is a view somewhat similar to FIG. 3 showing the handle assembly and trigger disposed in an alternative position.  
 DETAILED DESCRIPTION OF THE DRAWINGS Referring first to FIG. 1, the rotary hammer includes a housing having mounted therein a motor and a tool holder and bit indicated generally at 14. The housing is formed in such a manner that it includes a handle portion 16, there being a motor control trigger l8 disposed within the handle portion 16, the trigger 18 being utilized to start and stop the motor 12. The motor disclosed in the drawings is a generally conventional electric motor which is interconnected with a source of electric power by line cord 20.  
  The tool holder 14 includes a spindle 22 which is rotatably journalled within the housing by bearings 24. A bit 26 having a hexagonal shank 28 is received within a corresponding hexagonal opening 30 of the spindle 22. The spindle 22 is provided with an enlarged opening 32 to the right of the hexagonal opening 30, the enlarged opening 32 receiving a beat piece 34. The beat piece 34 can reciprocate within the enlarged opening 32 and it is provided with seals 36. The beat piece is provided with an impact surface 38 on its left hand side as seen in the drawings which is adapted to contact an impact surface 40 on one end of the bit 26. The right side of the beat piece is also provided with an impact surface 42 which is adapted to be contacted by a ram or striker 44. A gear 46 is mounted upon the exterior of the spindle 22. It should be appreciated at this point that the bit 26 can be rotated about its axis 48 by driving the gear 46. It should also be appreciated that the bit 26 can be impacted longitudinally of its axis 48 by impacting the beat piece 34 with the ram of striker 44.  
  The motor 12 is mounted within the housing in a manner not material to the present invention and includes an armature shaft 50 which is in part supported by a bearing 52. The upper end of the armature shaft 50 is provided with a gear 54 which engages a gear 56. The gear 56 is mounted upon a stub shaft 58 that is supported for rotational movement about its axis by bearings 60 and 62.  
  First drive means, indicated generally at 64, are provided to cause the bit within the tool holder to be impacted longitudinally of its axis 48. The first drive means includes a crank pin 66 carried by the gear 56 to one side of its axis of rotation, the crank pin 66 being in turn interconnected with a connecting rod 68 by bearing 70. The other end of the connecting rod 68 is interconnected with a piston 72 by means of a wrist pin 74. The piston 72 is disposed within a cylinder 76, and the ram or striker 44 is also disposed within the cylinder 76. An air chamber 78 is formed within the cylinder 76 between the left face 80 of the piston and the right face of the striker 44. As the piston 72 is reciprocated back and forth within the cylinder 76 the air chamber 78 will have its air pressure increased above and decreased below atmospheric pressure which will in turn cause the striker 44 to reciprocate within the cylinder. Thus as the piston is moved to the right from the position shown in FIG. 1, due to rotation of the pinion gear 56 by the motor 12, the pressure within the air chamber 78 will be initially decreased causing the striker 44 to move to the right under the action of atmospheric air pressure. After the piston has moved all the way to the right and is then caused to be moved to the left the pressure within the chamber 78 will be caused to be built up above atmospheric air pressure forcing the striker to the left until the face 84 of the striker impacts the impact surface 42 of the beat piece 34. This will in turn cause the bit to be impacted longitudinally of its axis 48.  
 Second drive means, indicated generally at 92, are  
 provided to cause the tool holder and bit to be rotated about axis 48 when the armature shaft 50 of the motor is rotated. To this end, it should be noted that the stub shaft 58 is provided with gear teeth 94 adjacent the lower end, the gear teeth meshing with teeth on the spur gear 96. The spur gear 96 in turn causes a stub shaft 98, which is mounted in spaced apart bearings 100, 102, to rotate through a friction clutch assembly indicated generally at 104. The friction clutch 104 is utilized to limit the torque which may be transmitted to the rotating bit. Mounted upon the stub shaft 98 and rotatable therewith is a first bevel gear 106 which meshes with a second bevel gear 108 carried by a bearing 110. A clutch assembly, indicated generally at 112, is interconnected with the bevel gear 108 and in turn causes the gear 46 to be rotated when the clutch is engaged.  
  The clutch means 112 includes a first rotatable driving element in the form of a drive sleeve 114 which is press flt about the hub 116 of the bevel gear 108. A rotatable output shaft 118 is journalled for rotation within the sleeve 114 and is keyed to the sleeve to prevent longitudinal movement of the output shaft 118 about its axis of rotation 120. To this end, the shaft 118 is provided with an annular groove 122 which is engaged by a transverse pin 124 carried by the sleeve member 114. It should be noted at this point that axis of rotation of the output shaft is substantially parallel to the axis of rotation 48 of the tool holder 22. A second driven element or sleeve 126 is disposed about the shaft 118. The sleeve 126 is mounted upon the shaft 118 in such a manner that it rotates with the shaft but may move axially of the shaft. To this end the shaft 118 is provided with a keyway 128, and similarly, the second sleeve 126 is provided with a corresponding keyway 130. A round key 132 is disposed within the keyways 128 and 130 and holds the sleeve 126 from rotation about the shaft 118. However, the sleeve 126 may be moved away from the first or drive sleeve 114 from the position shown in FIG. 1 to the position shown in FIG. 2 against the action of a compression spring 134. The right hand end of the spring 134 bears against the left hand face 136 of the second sleeve 126, and the left hand end of the spring 134 bears against the corresponding face of a race 138, the race 138 being in turn journalled for rotation within the housing by roller bearing 140. The race 138 and roller bearing 140 also support the left hand end of the output shaft. The left hand end of the drive sleeve 114 and the right hand end of the driven sleeve 126 are provided with interengaging clutch faces in the form of a dog clutch with straight teeth, that is to say that the ends are provided with teeth having sides disposed in planes which extend through the axis 120 of the shaft 118. The clutch faces for the sleeves 114 and 126 are best indicated at 142 and 144 in FIG. 2. The output shaft 118 is provided with gear teeth 146 which mesh with the teeth on gear 46. Rotation of the armature 50 of the motor will cause the drive sleeve 114 to rotate by means of the gear 56, stub shaft 58, spur gear 96, friction clutch 104, stub shaft 98, and bevel gears 106 and 108. If the driven sleeve 126 is in engagement with the drive sleeve 114, the second sleeve will in turn drive the output shaft 118 through key 132, the output shaft in turn causing the gear 46 to rotate through the splines 146.  
  To disengage the clutch it is necessary to shift the second sleeve from its right hand position shown in FIG. 1 to its left hand position shown in FIG. 2. To this end, trigger means are provided, the trigger means being indicated generally at 148. The trigger means include a pivoted trigger 150 having a first portion 152 disposed within the housing 10. As the trigger 150 is pivoted from the position shown in FIG. 1 to the position shown in FIG. 2, the first portion 152 will bear against the annular abutment 154 formed on the second sleeve 126 forcing the second sleeve to the left. It should be noted that once the clutch means is in its declutching position shown in FIG. 2, that the first portion 152 of the trigger 150 will not be bearing against a rotating surface. Thus, when the second sleeve 126 is in its declutched position, it will not be caused to be rotated by the drive sleeve 114. The trigger 150 is pivoted about a transversely extending pivot pin 156 which is supported by mounting means which includes a trigger housing 158. The mounting means also includes a cylindrical member 160 which is disposed within the housing 10 for rotation about its axis and is held from longitudinal movement by a spacer 162 which is disposed between one end of the cylindrical member 160 and the bearing 110, and is also held from longitudinal movement by an abutment surface 164 formed in the housing 10. A torque taking handle assembly, indicated generally at 166, is also interconnected with the mounting means, the torque taking handle assembly including a handle portion 168 which is rigidly molded about a shaft 170, threaded at one end. The threaded shaft 170 engages a threaded opening formed in a sidewall of the cylindrical member 160. The cylindrical member also includes an opening 171 to one side of the threaded opening, the first portion 152 of the trigger 150 extending through the opening 171. The shaft 170 is provided with an abutment surface 172 which bears against a washer 174 disposed between the molded handle 168 and the trigger housing 158. The trigger housing 158 includes side members 176 which bear against one of a plurality of mating surfaces 178a, 178b, and 1780. In FIG. 3 the side members are shown abutting against surface 178b and when in this position the handle assembly will be disposed in a position parallel with the handle portion 16. In FIG. 4 the side members are shown abutting against surface 178(- and when in this position the handle 168 will extend outwardly to one side of the rotary hammer. In order to shift the handle to the various positions, it is necessary to unthread the shaft 170 from the threaded aperture in the cylindrical member a sufficient amount so that the trigger housing may be swung from one position to the other. After the handle has been disposed in its desired position it is only necessary to tighten the handle into the threaded aperture an amount sufficient to lock the assembly in the desired position. When in the locked position the cylindrical member 160 and trigger housing will be firmly in engagement with corresponding portions of the housing 10 as shown in FIG. 3. The housing is provided with an open C-shaped slot 180 to permit the torque taking handle assembly and trigger to be swung to its various positions, a portion of the shaft and the portion 152 of the trigger 150 passing through the slot.  
  It should be appreciated at this point that by disposing the axis of the output shaft 118 parallel to the axis of rotation 148 of the tool holder 22 that not only is a compact structure achieved, but that also the torque taking handle assembly 166 and the trigger 150 may be swung to various positions for the convenience of the operator as the cylindrical member 160, which supports the trigger housing, is rotatable about the shaft 118. The trigger, which includes a second portion 182 disposed outwardly of the housing, can be easily engaged by the forefinger of the operators hand which is holding the handle 168 in each of the various positions of the handle 168 to facilitate easy clutching or declutching the assembly.  
  Referring again to-FIG. 1. it should be noted that the trigger 150 is normally biased to a position wherein the first portion of the trigger 152 is not in contact with the annular abutment 154 of the driven sleeve 126 when the parts are disposed in their clutching position. This biasing is accomplished by a spring 184 disposed within the trigger housing, one end of the spring 184 bearing against a cylindrical extension 186 of the trigger housing 158 and the other end of the spring 182 being received within a cylindrical aperture 188 in the trigger 150. Thus, the portion 152 of the trigger does not normally bear against any rotating parts when the tool holder and bit are being rotated.  
  It should be noted that during normal operation of the rotary hammer, that is to say, when the tool holder is being rotated, that there are no internal frictional forces in the clutch assembly 112. Thus, the spring 134 which biases the second sleeve member 126 into its clutching position will rotate with the driven member 126 and the inner race 138 as the shaft 118 is caused to be rotated.  
  The operation of the rotary hammer disclosed in this application should be obvious from the aforegoing. While a preferred structure in which the principles of the present invention have been incorporated as shown and described above, it should be understood that this invention is not limited to the particular details shown and described above, but that, in fact, widely different means may be employed in the broader aspects of this invention.  
 What is claimed is:  
 1. A rotary hammer comprising:  
 a housing;  
 a bit mounted within the housing and rotatable about its axis of rotation and reciprocal longitudinally of its axis of rotation;  
 a motor mounted within the housing;  
 first drive means interconnecting the motor with the bit and operable to impact the bit longitudinally along its axis of rotation upon rotation of the motor;  
 second drive means interconnecting the motor and the bit, said second drive means including clutch means having a rotatable driving clutch element and a rotatable driven clutch element movable between a first clutching position wherein it is caused to be rotated by said driving element and a second declutching position wherein it is not rotated, said second drive means being operable to cause the bit to rotate about its axis of rotation upon rotation of the motor when said clutch elements are in their clutching position;  
 trigger means pivotally mounted on the housing and having a first portion disposed within the housing and engageable with said driven clutch element and second portion disposed outwardly of the housing and manually engagable to move the driven clutch element away from the first clutch element to disengage the drive to the bit, and means for mounting said trigger means in various fixed positions about the housing.  
  2. The rotary hammer set forth in claim 1 further characterized by the provision of spring means which normally biases the driven clutch element into engagement with the driving clutch element.  
  3. The rotary hammer set forth in claim 2 wherein the spring means and the driving and driven clutch elements are all disposed about an output shaft, means mounting said driving clutch element on said output shaft in such a manner that it is held from longitudinal movement about the axis of the output shaft, and means holding one end of said spring means against longitudinal movement on said output shaft, the parts being so arranged and constructed that when said clutch means is in its clutching position the thrust forces exerted by said spring means are received by the output shaft in such a manner that no internal frictional forces are created.  
  4. The rotary hammer set forth in claim 1 wherein spring means normally biases the first portion of the trigger means out of engagement with the driven clutch element.  
 5. A rotary hammer comprising:  
 a housing;  
 a bit mounted within the housing for both rotational movement about its axis and reciprocatory motion longitudinally of its axis;  
 a motor mounted within said housing;  
 first drive means interconnecting the motor with the bit and operable upon rotation of said motor to impact said bit longitudinally of its axis;  
 second drive means interconnecting the motor and the bit, said second drive means including clutch means movable between engaged and disengaged positions, and said second drive means being operable upon rotation of the motor to cause the bit to rotate about its axis when said clutch means is in its engaged position;  
 a torque taking handle assembly extending away from said housing;  
 trigger means having a first portion interengagable with said clutch means, and a second portion manually engagable to cause the first portion to selectively engage and disengage said clutch means;  
 mounting means for mounting both the torque taking handle assembly and the trigger means on the housing with a portion of the torque taking handle assembly being disposed adjacent the second portion of the trigger means, and means for mounting said handle assembly and the trigger means in various selected fixed positions about said housing whereby the torque taking handle assembly and the trigger means may be disposed in a position to suit the convenience of the operator.  
  6. The rotary hammer set forth in claim 5 in which said mounting means includes a cylindrical member disposed within said housing for rotatable movement about a portion of said second drive means, a trigger housing disposed to the outside of said first housing, and further characterized by the provision of means operable to bias the cylindrical member and the trigger housing towards each other whereby the cylindrical member and the trigger housing are clamped about a portion of said first mentioned housing.  
  7. The rotary hammer set forth in claim 6 in which said means operable to bias the cylindrical member and the trigger housing towards each other includes a shaft threaded on one end, a threaded aperture in a side of said cylindrical member which receives the threaded end of the shaft, and an abutment surface on said shaft which bears against said trigger housing.  
  8. The rotary hammer set forth in claim 5 wherein said housing and said mounting means include mating surfaces which facilitate holding the mounting means in its related fixed position.  
 9. A rotary hammer comprising:  
 a housing;  
 a bit mounted within the housing for both rotational movement about its axis and for reciprocal motion longitudinally of its axis;  
 a motor mounted within the housing;  
 first drive means interconnecting the motor with the bit and operable upon rotation of the motor to impact the bit longitudinally of its axis;  
 second drive means interconnecting the motor with the bit and selectively operable upon rotation of the motor to rotate said bit, said second drive means including a rotatable shaft having an axis of rotation generally parallel to the axis of rotation of the tool holder, a drive sleeve journalled for rotation about said shaft, said drive sleeve having a clutch face on one end, and a driven sleeve rotatable with said shaft and mounted about said shaft for axial shifting&#39;movement, said driven sleeve having a clutch face on one end thereof; and  
 means selectively operable to shift said driven sleeve longitudinally about the shaft between a first position where the clutch faces on the drive and driven sleeves are in engagement with each other whereby the bit may be rotated upon rotation of the motor and a second position where the clutch faces are disposed away from each other whereby the rotary drive to the tool holder is disengaged.  
  10. The rotary hammer set forth in claim 9 wherein the means operable to move the driven sleeve towards and away from the drive sleeve includes trigger means mounted on the housing and having a first portion disposed within the housing and engagable with said driven sleeve and a second portion disposed outwardly of the housing and manually engagable by the operator of the rotary hammer.  
  11. The rotary hammer set forth in claim 10 wherein the means operable to move the driven sleeve towards and away from the drive sleeve further includes spring means mounted concentrically about said shaft and operable to normally bias said driven sleeve into engagement with said drive sleeve.  
  12. The rotary hammer set forth in claim 10 wherein the trigger means further includes spring means normally biasing said first portion of the trigger means out of engagement with the driven sleeve.  
 13. A rotary hammer comprising:  
 a housing;  
 a bit mounted within the housing for both rotational movement about its axis and for reciprocal motion longitudinally of its axis;  
 a motor mounted within the housing;  
 first drive means interconnecting the motor and the bit and operable to impact the bit upon rotation of the motor;  
 second drive means including clutch means operable to rotate said bit upon rotation of the motor when said clutch means is engaged and inoperable to rotate said bit when said clutch means is disengaged;  
 handle means disposed outwardly of the housing;  
 trigger means operable to cause said clutch means to be moved between its engaged and disengaged positions; and  
 mounting means for mounting the handle means and the trigger means in various selected fixed positions about the housing.  
  14. The rotary hammer set forth in claim 13 in which said mounting means includes a cylindrical member disposed within said housing and a trigger housing disposed to the outside of said first mentioned housing, and further characterized by the provision of means operable to bias the cylindrical member and the trigger housing towards each other whereby the cylindrical member and the trigger housing are clamped about a portion of said first mentioned housing.  
  15. The rotary hammer set forth in claim 14 in which said means operable to bias the cylindrical member and the trigger housing towards each other includes a shaft threaded on one end, a threaded aperture in a side of the cylindrical member which receives one end of the shaft, and an abutment on said shaft which bears against the trigger housing.  
 16. A rotary hammer comprising:  
 a housing;  
 a bit mounted within the housing for both rotational movement about its axis and reciprocal motion longitudinally of its axis;  
 a motor mounted within the housing;  
 first drive means interconnecting the motor and the bit and operable to impact the bit upon rotation of the motor;  
 second drive means including clutch means operable to rotate said bit upon rotation of the motor when said clutch means is engaged, said second drive means including a rotary output shaft whose axis of rotation is parallel to the axis of rotation of the bit. and a clutch member slidable about the output shaft between an engaged position wherein the output shaft is caused to be rotated upon rotation of the motor and the disengaged position wherein the output shaft is not rotated;  
 handle means disposed outwardly of the housing;  
 means mounting the handle means in selected fixed positions about the output shaft; and  
 trigger means carried by said last mentioned means and operable to cause said clutch member to be moved between its engaged or disengaged positions.  
  17. In a portable power-operated tool having a housing, a motor in the housing, a tool bit chucked in the housing, drive means between the motor and the tool bit for rotatably driving the bit, clutch means in the drive means, a first handle provided with a first trigger means for controlling the energization of the motor, and a second handle mounted forwardly of the first handle for manually supporting the tool, the improvement which comprises a second trigger means mounted on the second handle and connected to the clutch means for selectively interrupting the drive means to the tool bit, in combination with means for conjointly adjusting the second handle and second trigger means in one of a number of desired positions substantially about the axis of the tool bit.