| 摘要 |
A cylindrical material (10) is sequentially subjected to a swaging treatment of (A) ?(B), a backward extruding treatment of (C) ? (D), a punching treatment of (D) ? (E), a rolling treatment of (E) ? (F), and a finishing treatment, thereby to manufacture an outer ring (3) constituting a double-row angular type ball bearing of back-combined type. A first intermediate material (11a) prepared by the swaging treatment is made to have an external diameter equal to or smaller than the internal diameter of an inner circumference side diametrically larger portion (18) of the inner circumference of a die (13) to be used in the backward extruding treatment, and larger than the internal diameter of a diametrically smaller portion (19) of the inner circumference side. In the backward extruding treatment, moreover, the first intermediate material (11a) is pushed, while its diametrically outer portion being hooked all over the circumference by an inner circumference inclined portion (20), toward the bottom portion of the die (13) by the leading end face of a punch (14). As a result, an intermediate metal material (29) of high cleanness in that material (10) is exposed to two outer ring races (2) of the outer ring (3). |
