| 摘要 |
The method is for manufacturing a rotor core having a cylindrical boss section formed with an axial hole, a disc section radially extending from one end of the boss section, and a plurality of claw sections provided along an outer periphery of the disk section. A boss section-side hole as a part of the axial hole is formed by plastic deformation in a preliminary shaping step. The remaining part of the axial hole of the billet disposed on a die is punched through using a center hole punch having a diameter smaller than an inner diameter of the boss section-side hole to form the disk section-side hole in the flush/punch through step, so that the axial hole is constituted of the boss section-side hole, the disk section-side hole and a step portion between the boss section-side hole and the disk section-side hole.
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