| 摘要 |
PURPOSE:To prevent generation of a rupture, peeling, etc., of a resin lubricating layer of a flange surface in a flange forming process, by providing an R recessed surface on a preforming punch, in a preforming process. CONSTITUTION:A preforming punch 17 provided with a columnar part 17a, a ring- shaped projecting part 17d which has been formed as one body in the end part of this columnar part 17a, and a small columnar part 17b which has been formed as one body with the columnar part 17a with an R recessed surface 17c from a base part of the ring-shaped projecting part 17d is prepared. Subsequently, the end part of a winding bush 1 which has been projected into a cylindrical recessed part of a cavity of a die 2 is deformed after the manner of the R part recessed surface part 17c of the preforming punch 17. In this state, an end face 1c of the winding bush 1 is detained so that a pressing force going toward the center of its cylinder is generat ed and an expanded diameter part 1d which has been opened in a funnel shape is formed. Thereafter, a flange forming is executed by a flange forming punch. In this way, a pressing force of the flange forming punch is not applied to only outside periph eral end face of the funnel-shaped expanded diameter part of the winding bush, there fore, a resin lubricating layer of the flange surface is finished beautifully without causing a rupture, peeling, unevenness, and scuffing.
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