| 摘要 |
PROBLEM TO BE SOLVED: To obtain the formation of even a hub high-clutch (hub assembly/high clutch) having the tip drawing part with a serration in >=30% reduction of area from a prefrom with only one time of pressurized operation. SOLUTION: The formation of the hub high-clutch is obtained through the following four stages. A first stage is performed, by which the tip part of a cylindrical shaft part 17a is inserted into the serration forming part 3c by simultaneously moving downward a mandrel 14 and a punch 13. A second stage is performed, by which the movement downward of the mandrel 14 and the punch 13 is continued, and the mandrel 14 is further moved downward so that a step part 19 formed at the boundary with the small diameter part 14a positions just before the serration forming part 3c in a cavity 3, then, a rim 21 is formed with a backward extrusion and also, the tip part of the cylindrical shaft part is further inserted into the serration forming part 3c with a forward extrusion. A third stage is continuously performed without stopping to which only the mandrel 14 is moved downward under state of leaving the punch 13 at the bottom dead center. Thereafter, at a fourth state, this hub high-clutch is removed from a die.
|
