| 摘要 |
PURPOSE:To reduce cost of working by forging circumferential projections on the outside of an annular material and forging projections corresponding to concave parts by passing a stepped mandrel, and thereby shifting outside projections to inside. CONSTITUTION:An even annular material 4 having inner diameter smaller than the inside diameter d1 of concave parts 3 inside of a ring 1 and thickness greater than that of convex parts 2 inside of the ring 1 is prepared to obtain a ring having inside projections. A mandrel 5 is passed throgh the annular material 4 and its outside is notched with an edge-shaped anvil 6. A mandrel 9 having diameter nearly equal to inner diameter of the annular material is passed through the notched annular material 8. While rotating the material 8, outside of the ring corresponding in position to inside concave parts 3 of the ring 1 is forged to a thickness greater than t1. The annular material having outside projections 12 thus obtained is forged between an anvil 13 and a stepped mandrel 14. At this time, convex parts 12a on the outer circumference of the material are placed against concave parts 14a of the stepped mandrel, and this part is forged while rotating the material 12 and converted to convex part on the inner circumference of the material. |
