A binding wire twisting apparatus for tying reinforcing bars. A motor rotates a shaft upon which a member reciprocates from a rearward to a forward position. The apparatus includes opposed fingers with opposed channels for fed binding wire. When in the rearward position, the member drives a wire feeding unit that feeds binding wire though the fingers and around the reinforcing bars. When the leading end of the fed wire impacts an actuator of a four-way valve, a pneumatic cylinder reciprocates the member from the first to the second position, and a cutter cuts the wire. Once in the second position, gripping surfaces entrap and hold the ends of the wire, and the rotating member, while holding the ends of the wire between first and second grip pieces, twists and ties the wire around the reinforcing bars, and a torque-release clutch decouples the motor from the shaft.