METHOD FOR MOLDING BOSS, MOLDED ARTICLE, AND APPARATUS FOR MOLDING INNER DIAMETER SPLINE TEETH

PROBLEM TO BE SOLVED: To provide a method for molding a boss in which a molded article can be prevented from deforming even if residual stress is released when subjected to a thermal treatment, such as induction hardening, and to provide a molded article, and an apparatus for molding inner diameter spline teeth.SOLUTION: The apparatus 10 for molding inner diameter spline teeth includes a top surface support member 11, a bottom surface support member 12, and a punch 21. A spline Ws to a workpiece W is formed such that the punch 21 is inserted from an end Wt of the workpiece W and the workpiece W is plastic-formed with a spline forming protrusion 22 provided at an end of the punch 21 to form the spline Ws. The punch 21 is provided with a protrusion 23 having an outer diameter larger than that of the protrusion 22 and formed entirely around the periphery close to the proximal end of the punch 21. Upon the completion of molding the spline Ws by the insertion of the punch 21 into the end Wt of the workpiece Wt, the spline Ws is subjected to plastic forming with the protrusion 23 so that the plate thickness of the end Wt around the entire periphery is made substantially even.