Patent ID: 8888566

Claim:
A power tool comprising: a tool body wherein the power tool performs a predetermined operation by driving a tool bit attached to the tool body via a first driving source, a grip coupled to the tool body, the grip being configured to be held by a user and a self-synchronous mechanism that reduces whirling vibration caused in at least one of the tool body and the grip when the tool bit is driven, wherein: the self-synchronous mechanism is defined by a phase variable type, having a rotating body as a vibrator which is rotationally driven by a second driving source that is different from the first driving source, wherein the self-synchronous mechanism is disposed in the at least one of the tool body and the grip where the whirling vibration is caused and is arranged such that a phase of vibration of the rotating body is automatically tuned to a phase of the whirling vibration to reduce the whirling vibration.