Tapping machine

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. The tapping machine is also provided with means for generating overload sensing signal when an interval between any two pulse signals from the pulse signal generating means exceeds a predetermined time duration, so as to backwardly rotate the motor immediately after the generation of the overload sensing signal, that is, an abnormal condition warning signal for returning the spindle to the start position.