US Patent 7565935 Powered tap driver with rotary control structure

The tap driver is configured to be hand-held. It has a tap-holding chuck and a motor to drive the chuck. An external switch rocks forward to rotate the motor in the tapping direction and backward to withdraw the tap. A control circuit causes forward motion of the tap for a predetermined time for the tap to make about one forward turn for tapping. At the end of that time, the motor reverses and rotates the tap outward a fractional turn to break the chips made during tapping. The timer then turns the circuit to drive the motor in the forward direction for another tapping. This action repeats until tapping is complete and the switch is rocked back to reverse the motor to withdraw the tap.