PURPOSE: To obtain a cup-shaped washer high in dimensional accuracy and excellent in quality by providing a separator through-hole having a folded and reinforced peripheral part and smaller in diameter than specified dimensions and finally pressing a die for remedying a hole diameter to a specified diameter into the through-hole to be finished.
CONSTITUTION: In a working area for a cup-shaped washer, a cup-shaped projection 13 is pressed and a prepared hole 15 of small diameter is made by a male trimming die 17 of a lower die 16 and a female trimming die 19 of an upper die 18 at a suitable place 14 of the bottom of the projection 13. The peripheral edge part of the prepared hole 15 is burred outward by a male burring die 20 of the lower die 16 and a receiving hole part 21 of the upper die 18 to form a cylinder part 22. The cylinder part 22 is folded outward by a male die part 23 of the upper die 18 and a forming recess part 24 to make a folded part 22a. The folded part 22 and a suitable place 14 on the bottom part of the cup-shaped projection 13 are pressed by a receiver part 25 of the lower die 16 and a receiver part 26 of the upper die 18 to be brought into contact with each other and to compose a through-hole 28 having a folded double structure peripheral part 27 and relatively small in diameter. A trimming die part 29 for remedying the hole diameter of the lower die 16 is pressed into the through-hole 28a, removed and finished into a separator through-hole having specified dimensions.
Kitao, Akira
Yanagihara, Takashi
