To improve the shape precision and the whole rigidity in a crutch hub while reducing a cost required for this formation as much as possible and preventing the lowering of the positional precision in the peripheral direction of each spline tooth, in the case of forming the crutch hub having the spline tooth on the outer peripheral part.
A workpiece material having a hollow cylindrical part 4c, a mandrel 11 and a rolling roller 13 are prepared, and a plurality of projecting parts 11a are beforehand formed with interval in the peripheral direction on the outer peripheral surface of the mandrel 11, and while shifting in the axial center direction as rotating around the axial center state of inserting the center part of the hollow cylindrical part 4c into the mandrel 11, the outer peripheral surface 13a of the rolling roller 13, is pushed on the outer peripheral surface of the hollow cylindrical part 4c, and thus, the material is fluidized into the flat surfaces 13f and the recessed parts 13d on the outer peripheral surface 13a while pushing the projecting part 11a into the portion corresponded to a tooth-part forming scheduled part on the internal peripheral surface 4L of this hollow cylindrical part 4c.
TANAKA YUKO
MORIHIRO SHINJI
Hiroshi Takeuchi
Takahisa Shimada
Yuji Takeuchi
Katsumi Imae
Atsushi Fujita
Kazunari Ninomiya
Tomoo Harada
Iseki Katsumori
Seki Kei
Yasuya Sugiura