Experimental Study of Tapping Wear Mechanisms on Nodular Cast Iron

Tapping by cutting is one of the most common operations in manufacturing. This multi-teeth tool, known as a tap, cuts the thread in a hole when the piece has a high added value. The thread quality is ensured when the tap is new or slightly worn, yet when tap wear is high; the quality of profiles exceeds tolerance limits and therefore a defect occurs in the manufacturing line. The aim of this paper is to study the tap wear of titanium nitride coated taps measured on nodular cast iron. The level of tap wear is determined by optical images and the wear mechanics are classified by scanning images and energy dispersion spectroscopy analysis. The results highlight that the critical part in measured taps is between the last chamfer and the first cylinder teeth and, consequently, the thread profile is under-sized. Beside adhesive wear, coating removal and chipping are the main wear aspects during tapping operations.