| 摘要 |
PURPOSE:To improve degree of coaxial relation of a spline and a center hole by providing expanding taper at the exit part of an extrusion die, providing thinning taper in a center hole forming punch and fitting the taper of the forming punch to the taper of the extrusion die. CONSTITUTION:A tapered part 10c that expands toward exit side is provided at the exit part of an extrusion die 10, and the tip 12b of a center hole forming punch 12 having thinning tapered part is fitted to the tapered part 10c. In a process that extrudes a work 2 by the extrusion die 10, extrusion process is made by pressing the work 2 against the forming punch 12, and at the same time, tapered parts of the extrusion die 10 and forming punch 12 are fitted together at the time of forming the center hole, and process of center hole forming is performed. Thus, the degree of coaxial relation between spline of the product and the center hole is improved, and the precision of tooth from of spline on the basis of the center hole can be improved. |
