Abstract: A tapping machine provided with a quill for rotatably supporting a spindle which holds a tap on one end thereof, a reversible electric motor for rotating the spindle and axially reciprocating the quill, an overload release clutch mounted in a power transmitting mechanism which is disposed between the quill and the motor, for suspending the power transmission between the quill and the motor when an overload is applied on the quill, and pulse signal generating means mounted between the clutch and the quill in the power transmitting mechanism for generating one pulse signal in response to each one pre-set unit distance of the quill during the forward motion thereof. The tapping machine performs a working cycle in good order wherein the spindle advances from the start position while being forwardly rotated until the number of pulse signals generated from the pulse signal generating means accords with a pre-set number and returns while being backwardly rotated back to the start position.

Abstract: A tapping machine having a spindle which is moved reciprocally, i.e., in advancing and retracting direction while being rotated forwardly and backwardly for forming a female screw in a work with a screw tap attached at one end thereof. The machine is provided with driving means including a reversible electric motor, position sensing means for generating a sensing signal when the spindle is moved in advancing direction from a start position so far as a predetermined position, and temperature sensing means for generating a sensing signal when the temperature of the electric motor has risen exceeding a predetermined value. The machine normally repeats a working cycle wherein the spindle is moved in advancing direction from the start position while being rotated in forward direction until it is retracted to the start position soon after a sensing signal from the position sensing means has been generated.