Patent ID: 7146838

Claim:
A method of forming a tooth profile, comprising the steps of: inserting a punch into a hole in a workpiece and loading said workpiece in a body assembly; pressing a splining segment of said punch into said hole in said workpiece by pressing said workpiece with a first die unit actuated by an actuator to cause material of said workpiece around said hole to plastically flow to form spline grooves in an inner circumferential surface of said hole; holding an inner end face of said workpiece around said hole on an upper surface of a second die unit against displacement of said workpiece pressed by said first die unit, and pressing an outer circumferential edge portion of said workpiece by arbitrarily adjusting a pressure applied from said first die unit to said workpiece to generate a moment on said workpiece; and correcting the inner circumferential surface of said hole with said spline grooves formed therein from a shape progressively reduced and tapered upwardly into a shape substantially parallel to an axis of said hole so that said hole has a substantially constant diameter throughout its axial length between said first die unit and said second die unit.