Method for Forming Through-Hole

摘要

A method for forming a through-hole on a work material using a drill having a drill head provided with a brazed-type cutting blade helps prevent generation of a spiral mark on an inner circumferential face of the through-hole and obtains a superior appearance and high working accuracy. In forming a through-hole H on a work material W by a drill head 1A with cutting blades 3A to 3C brazed to cutting blade mounting seats 13a to 13c, a drill head provided with roundness R on a blade edge outer end portion 31a of a cutting blade 3A responsible for cutting of the outermost periphery is used as the drill head 1A.