Influence of drill geometry parameters on helical point micro drilling performance

Helical point micro-drill is characterized by a continuous helical flank instead of the piecewise planar flank, and its improved drilling performance is validated compared with planar drill point by some researchers. In this study, to analyze the effect of geometry parameters of helical point drill on the drilling performance, the micro-drills with different point angles, web thicknesses and helix angles of the flute are fabricated on a 6-axis CNC tool grinder, and a serial of micro-drilling experiments involving these drills on 1Cr18Ni9Ti austenitic stainless steel are carried out. In experiments, the drilling forces are measured and exit burrs are observed. Within a certain range of geometry parameters, thrust force increases with the increase of point angle and web thickness, and the decrease of the helix angle of the flute. The point angle is the main contributory factor for the thrust force followed by web thickness, while helix angle has a moderate effect on the force. Furthermore, poisson burr and rollover burr are generated with different point angles. Based on the results, a good selection of the helical point drill geometry parameters with small point angle, big helix angle and small web thickness are proposed to improve the micro-drilling performance.