COLD FORMING METHOD OF SPLINE SHAFT OR SPLINE SHAFT PROVIDED WITH CONDUCTION PARTS

摘要

PURPOSE:To cold-form precisely a spline shaft on which a prescribed male spline tooth is formed, by providing concentrically a conical projection on the end face of a counter punch, and pressing a stock into a shaft forming hole by a pressure which increases successively as the forming advances. CONSTITUTION:In a lower die 6, a circular counter punch 3 is fitted and positioned fixedly in the lower end part of a female spline tooth form 2 provided continuously in a shaft forming hole 1 of a die 12, and a conical projection 4 whose face angle is an acute angle is provided concentrically on the top face of the counter punch 3. A stock 7 inserted and placed in the shaft forming hole 1 is pressed by a upper die 9 and the lower die 6. When a pressing force of the stock 7 increases, the conical projection 4 starts to work jointly, and a male spline tooth (a) is formed on the outside peripheral part of a male spline forming part 7b. In this case, the lower face of a base material head part 7c contacts roughly to the upper face of a projecting line 23, a round rod part 7a is upsetted preventing a deformation of the male spline tooth (a), the round rod part is packed in the shaft forming hole 1, and also an oil groove 22 is formed on the lower face of the stock head part 7c.