Real time diagnosis charts of thread quality in tapping operations

Tapping by cutting is one of the most common operations in manufacturing. It consists of cutting internal threads on the wall of a previously drilled hole by means of a tool called a tap that has cutting edges on its chamfered periphery. When tap wear is slight the process and geometry are usually in control and correct, respectively. However, when tap wear level is high the geometry is not correct and the process is out of control. This is an unacceptable industrial cost. The aim of this paper consists on an industrial monitoring application to data coming from the current/torque signal of the tap spindle for assessing thread quality. It operates in real time and indicates when the tap wear is so critical that, if the process were continued, it would result in unacceptable screw threads. Then the system shows a red light so that the operator could replace the worn-out tap. The system would be very cost-effective since the tapping process could be run without any operator intervention.