Patent ID: 6851343

Claim:
A screwdriver, comprising: a motor, a body that houses the motor, a first spindle that can rotate and move relative to the body, a first clutch member disposed on one end portion of the first spindle, wherein the first clutch member rotates together with the first spindle while being allowed to move relative to the first spindle in the axial direction of the first spindle, a tool bit connected to the other end portion of the first spindle to perform a screw tightening operation, a second spindle connected to the motor to receive the rotating torque of the motor, a second clutch member that rotates together with the second spindle while being allowed to move relative to the second spindle in the axial direction of the second spindle, wherein the second clutch member is engaged with the first clutch member when the first spindle moves toward the body to transmit the rotating torque of the motor to the tool bit, a clutch engagement preventing member that urges the first clutch member and the second clutch member away from each other, the screwdriver being selectively operated in one of a first power transmission mode and a second power transmission mode, wherein in the first power transmission mode, the first clutch member and the second clutch member engage with each other to transmit the rotating torque of the motor to the tool bit, while the first and second clutch members are disengaged from each other when the reaction torque applied from the work-piece onto the tool bit exceeds a predetermined torque, and in the second power transmission mode, the first clutch member and the second clutch member engage with each other to transmit the rotating torque of the motor to the tool bit, while the clutch members are disengaged from each other when the tool bit moves a predetermined distance away from the body toward the work-piece during the screw-tightening operation.