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Wear and progression of life of plasma nitrided four-faceted high-speed steel drills with varying geometries

TiN-coated high-speed steel drills are known to give improved performance. However, when coatings are coupled with a careful selection of drill geometry parameters, the performance can be improved further. Consequently, in this work, progression of flank wear land width on four-faceted split-point plasma nitrided high-speed steel drills with varying point and helix angles in drilling of SS304 was analyzed along with a conventional drill with a point angle of 118°. Elaborate experimentation was undertaken to test the drills and capture the effect of flank wear on the drill performance. The drills with moderate point angle of 124° outperformed other drills with point angles of 130° and 118°. As the wear progresses, the thrust and torque show a minor increase in the case of four-faceted drills as compared to the conventional drills. Abrasion and chipping were found to be the dominant wear mechanisms while drilling SS304, whereas major drill failure mechanisms appear to be excessive abrasive wear followed by chipping.