Abstract: Chisel edge thinning is an efficient means to improve the machining performance of drilling tools. As for the high-aspect-ratio micro-drill with thinned chisel edge, the mathematics models of helical flute, non-coaxial helical flank and cross-shaped chisel edge are established, and the micro-drills with diameter of 0.5 mm and aspect ratio of 10 are fabricated by a six-axis CNC grinding machine. The comparative drilling experiment is carried out on 304 stainless steel using high-aspect-ratio micro-drills with and without thinned chisel edge, and the influence of chisel edge thinning on the drilling performance of high-aspect-ratio micro-drill is analyzed from the aspects of thrust force, tool wear and machining quality of micro deep hole. The results show that the thrust force and drill tip wear of the high-aspect-ratio micro-drill with thinned chisel edge are dramatically reduced compared to the ordinary micro-drill. After drilling five micro deep holes, the maximum wear width of the drill flank and chisel edge of high-aspect-ratio micro-drill with thinned chisel edge is reduced by 26% and 32%, respectively. And the micro deep holes obtained by the micro-drill with thinned chisel edge, have better entrance shape, lower micro-hole roundness and hole-wall roughness. It is demonstrated that the chisel edge thinning method can significantly improve the drilling performance of high-aspect-ratio micro-drill.

Key words: micro deep hole, high-aspect-ratio micro-drill, chisel edge thinning, cutter grinding, drilling performance