Method of forming internal spline shaft

摘要

A method of forming an internal spline shaft, comprising forming splines on an inner circumferential portion of a hollow stock by cold forging in such a way that a clearance "a" between an inner diameter of the hollow stock and an outer diameter of a tool guide portion, a difference "b" between a reduced diameter of a forming land and the inner diameter of the hollow stock, and a forming-land approach angle theta satisfy respectively specific relationships. By this method, products having internal long splines can be obtained in a high yield by cold forging method.