| 摘要 |
A cylindrical clutch drum of a clutch for an automatic transmission is formed with a plurality of spline grooves by press forming. Each spline grooves consists of a series of groove portions arranged, end to end, in a line. The width and depth of each spline groove are increased in a stepwise manner, one groove portion after another, toward one groove end. Each groove portion is made by half-blanking with a die having a width corresponding to the width of the groove portion and a length corresponding to the length of the groove portion. Instead of the spline grooves, the clutch drum may be formed with axially extending openings made by blanking. In this case, the width of each opening is increased in a stepwise manner.
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