To produce a spring washer blind hole of a piston for an automobile change gear by extrusion with a pin, to solve an unbalanced load to the pin and to solve the problem of deformation and shrinks by the material fluidized by the extrusion at that time.
The circular region along the circumferential edge at the back face of the tip face plate part 3c in a secondarily worked body is flatly formed, then, the secondarily worked body is placed on a lower die 11f and is also pressed by upper dies 10f, 10g, then, while applying cushion pressure to the lower die 11f, and from the back face side of the tip face plate part 3c of the secondarily worked body, a spring washer blind hole working pin 13 is allowed to perform an extrusion working operation thereto, and the extruded material is fluidized to the blind hole 10f1 of the upper die 10f, so as to make a spring washer blind hole. Thereafter, a projecting part 3cp fluidizedly projecting to the front side is removed by machining with a lathe.
HIYAMA YOSHIKI
TANABE KENTARO
KANZAKI YOSHIYUKI
SATO SATOSHI
YAMAZAKI HITOHISA
GOTO KIICHIRO
NOK CORP
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