Cutting edge preparation using magnetic polishing and its influence on the performance of high-speed steel drills

The purpose of this paper is to investigate the effects of cutting edge preparation on tool life and tool wear of HSS drills. The experiment first utilized an unconventional but cost-effective method of magnetic polishing for cutting edge preparation on HSS drills. Observations from SEM and profilometer showed that magnetic polishing can generate different sizes of cutting edge radii for HSS drills. Its polishing effectiveness depends on the shot media, the severity of mechanical impacts and polishing time. The polished edge-radiused drills demonstrate a remarkable improvement in tool life compared to unpolished sharp drills. For the drilling conditions investigated, edge radius ranged between 24 and 27 μm has the highest tool life performance. The performance of different drills was also assessed by the measurement of thrust and torque, hole diameter, surface roughness and drill wear. Results show that large edge-radiused drills are prone to produce undersized holes. However, for the same amount of flank wear, all edge-radiused drills initiate lower thrust force and torque increment than the unpolished sharp drill therefore they can tolerate larger flank wear and lengthen the tool life.