Patent ID: 7694750

Claim:
A hammer drill comprising: a motor; a spindle rotatingly driven by the motor and holding an output bit; a motion conversion member for converting rotational movement of the motor to reciprocating movement; a striker reciprocatingly driven by the motion conversion member for applying an axial striking force to the output bit; a striking-motion-releasing mechanism for releasing the striking force applying action exercised by the striker; a tightening-torque adjusting clutch for interrupting the transfer of the rotational force to the output bit by increasing a load torque; and a clutch handle for adjusting a fastening torque of the tightening-torque adjusting clutch, wherein when the striking force applying action is not released, the fastening torque is not allowed to be adjusted by the clutch handle, and when the striking force applying action is released, the fastening torque is allowed to be adjusted by the clutch handle, wherein the tightening-torque adjusting clutch is adapted to directly couple a driving side to a driven side at the time when the striking force applying action is not released, so that the fastening torque is not adjusted by the clutch handle, wherein the driving side is rotated by the motor, and the driven side is rotated by the driving side to rotate the spindle, wherein the hammer drill further comprises a pin commonly located inside both a hole of the driving side and a hole of the driven side when the driving side and the driven side are directly coupled, and wherein the tightening-torque adjusting clutch is adapted to directly couple a driving side to a driven side at the time when the striking force applying action is not released, so that the driving side does not slip over the driven side.