Abstract: A speed-increasing mechanism and a clutch mechanism are provided between a speed-reduction gear train and planetary gear trains, to realize a small-torque and high-speed rotation during a light load condition and a large-torque and low-speed rotation during a heavy load condition. A motor is actuated by a relay. An auxiliary motor switch, closing a contact of the relay, is provided at a motor housing to facilitate an operation of a shear wrench during a work where a bolt is fastened upward from below.

Abstract: A connector comprises a plug and a socket. The plug has a main plug body, a plurality of contact pins projecting from the main plug body and including a contact pin for grounding, and a shielding member surrounding the plurality of contact pins. The socket has a main socket body, a plug receiving part provided on the main socket body for receiving the shielding member, a plurality of contact portions provided within the plug receiving part for making contact with corresponding ones of the plurality of contact pins and including a first contact portion for making contact with the contact pin for grounding, and a second contact portion provided on the main socket body for making contact with the shielding member. The plug is detachably coupled to the socket by inserting the shielding member into the plug receiving part. The first and second contact portions are made of a single contact member.