| 摘要 |
The inner peripheral surface of the larger-outer-diameter portion 11a is pressed against the upper forming portion 20 of the sizing core rod 12, so that the bearing surface of a shape corresponding to the forming portion 20 is formed in the inner peripheral surface. As the upper punch 14a and the sizing core rod 12 are further moved in operative association with each other, the end of the smaller-outer-diameter portion 11b reaches the tapered portion 21b1 of the drawing portion 21b, so that it is subjected to a radially inwardly directed pressurizing force. Thereby, the inner peripheral surface of the smaller-outer-diameter portion 11b is pressed against the lower forming portion 20 of the sizing core rod 12, so that the bearing surface of a shape corresponding to the forming portion 20 is formed in the inner peripheral surface.
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