Study of hole tapping in SUS304 stainless steel

Abstract

This study was performed to clarify the effects of the coating film properties on tapping tool adhesion and tapping torque, and the relations between mechanical properties of coating films and results of tapping tests. A series of hole tapping tests in SUS304 stainless steel were performed using non-coated, TiN-coated, DLC-coated, and TiN/DLC-coated taps. The adhesion area on the flank face and the tapping torque were smaller when tapping with coated than with non-coated taps. Spot-like adhesion occurred on the entire flank face of TiN-coated taps. On the other hand, adhesion occurred only near the cutting edge on the flank face of DLC-coated taps and TiN/DLC-coated taps. TiN/DLC coated taps had the smaller adhesion area on the flank face. The adhesion area on the flank face decreased with decreasing ratio of the friction coefficient obtained from friction tests to the peeling critical load obtained from scratch tests of the coating film.