Patent ID: 7131503

Claim:
An impact driver comprising: a motor housed in a housing; an output shaft protruding from the housing and provided so as to slightly move back and forth in the axial direction; a rotation impact mechanism for transferring a motor torque to the output shaft while applying the impact operation in the rotative direction in accordance with increase of a torque load on the output shaft, a percussion application mechanism for generating percussion to the output shaft in the axial direction in accordance with rotation of the output shaft, and a regulating means, provided with the housing, which can from outside the housing arbitrarily select between a percussion mode in which the percussion application mechanism is activated and a non-percussion mode in which the percussion application mechanism is stopped, wherein the percussion application mechanism comprises: a first cam externally provided at the output shaft for rotating integrally with the same, a second cam inserted into the output shaft with play at the rear of the first cam, and the second cam is regulated in its moving in the axial direction, cam gears formed on the first and second cams at opposing faces thereof for contacting with each other at the backward position of the output shaft, and wherein by means of the regulating means, the percussion mode can be selected for regulating the rotation of the second cam and the non-percussion mode can be selected for releasing the regulation of the rotation of the second cam.