| 摘要 |
PROBLEM TO BE SOLVED: To attain the optimum decentralization of each step by reducing the forming rate of a fourth step of forming a ball rolling groove. SOLUTION: In a first step, a work 10 is subjected to the forward extrusion to form a first formed article 40, and in a second step, the upset forming is performed to form a second formed article 50. Successively, in a third step, the preliminary extrusion is performed on an upper face of the second formed article 50 to form a third formed article 60 in which a recess 62 substantially matched with the longitudinal sectional shape in the axial direction of a bottom wall 32 of a cup part of a final product is formed in the upper face. In a fourth step, the backward extrusion is performed on the third formed article 60 by using a punch having a tip shape substantially matched with the longitudinal sectional shape of the recess 62 to form a fourth formed article 70 having a cup part with a ball rolling groove formed in an inner wall thereof. Finally, in a fifth step, the cup part of the fourth formed article is ironed to manufacture an outer wheel member 12 as the final product. COPYRIGHT: (C)2007,JPO&INPIT |
