| 摘要 |
PURPOSE:To surely form a perfect valve seat face shape and to reduce the variance in shapes by subjecting a relief valve fitting part to finish forming in a perfect shape with forging together with a machining reference face. CONSTITUTION:A shot peening is executed on a blank, a hot forging temp. zone is subjected to high frequency heating and each forging stage of preforming, forming and punching is carried out to obtain a rough shaped clutch piston 1 with excess metal 10. Thereafter, the shot peening is executed once again on this forged clutch piston 1 for removing scales and sizing is executed further. This sizing is executed for obtaining the valve seat faces 24, 25 in the specified shape at the specified position without spoiling the positional accuracy of a relief valve fitting part 2. The clutch piston 1 is thus finished in a perfect dimensional shape with the relief valve fitting part and corner part keeping the specified relative position.
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