Improvement of Tool Life and Exit Burr using Variable Feeds when Drilling Stainless Steel with Coated Drills

Variable feed machining is a significant method for improving the cutting tool life and exit burr height for hard and difficult to machine materials. Four coated drills were tested in the present study, namely, TiN, TiCN, CrN, and TiALN. The results indicate that the amplitude of variation of feed, a = 0.6, is optimum for maximum tool life or minimum burr height. TiN-coated or TiCN-coated drills were superior to CrN-coated or TiALN-coated drills when drilling stainless steel. The chisel wear and the outer corner wear were the dominant mechanisms of the drill wear.