Method of forming a tappet in an internal combustion engine

摘要

An Al alloy tappet used in an internal combustion engine has a spiral groove on the outer circumferential surface of a tappet body. The spiral groove is formed by pushing a cutting tool against the outer circumferential surface and feeding it in an axial direction. Near the lower end of the tappet body, feed rate is decreased, and the cutting tool is moved away from the tappet body to form a smaller spiral groove which increases in diameter downwards. The outer circumferential surface of the tappet body is covered with a coating layer such as Fe, and the lower end which has the smaller spiral groove is chamfered.