| 摘要 |
PURPOSE:To improve accuracy of arching concave part in forming an arching concavity for fitting a ball on the inner race and ball fitting concavity at the tip of a rodlike material by providing an auxiliary concavity at a position corresponding to rising edge on both sides beforehand. CONSTITUTION:A preparatory concavity 5 having circular sectional form is formed by a plunger punch etc. at the tip of a columnar rodlike material. After this, or at the same time, auxiliary concavities 8 are formed by plastics working etc. at plural places on the outer periphery of the concavity 5 on the rising edges on both sides of an arcuate concave part 2 parallel to the axis of the material 1. Concavities 8 are formed to specified width on the outside of ball contact angle theta+2alpha at the time of operation, and the depth K is so determined that it remains after formation of the part 2, and at a specified angle beta. Next, a preparatory auxiliary concavity 9 is formed outside of the concavity 8 with depth (n) that remains in the final stage of plastic working, width (m), and inclination of both edges gamma. When a forming die is inserted into the concavity 5 of the arching concave part 7 and formed by pressing from outer periphery side, elastic contraction of the forming die is restrained by concavities 8, 9. Thus, accuracy of products can be improved remarkably. |
