| 摘要 |
PROBLEM TO BE SOLVED: To carry out a highly accurate, high speed working while restraining occurrence of flash or burr by forming a verge shape portion at a position offset to either one of a pair of openings on a bottom hole and punching the verge shape portion from the opening side near the position where the verge shape portion is offset. SOLUTION: A bottom hole punch 10 is provided with an upper mold 6 and a bottom hole die 13 is provided with a bottom mold 8. A flat part 11 is provided with the upper mold 6 and, a coining work punch 14 is provided with the bottom mold 8. A hole punching punch 12 is provided to the upper mold 6, and a hole punching die 15 is provided to the bottom mold 8. On a plate member 2 being pressed with the bottom hole punch 10 of the upper mold 6 and the bottom hole die 13 of the bottom mold 8, a bottom hole is opened. In the bottom hole thus formed, an opening is formed to the plate member 2 with the bottom hole punch 10 and the bottom hole die in such a way that the opening thereof is smaller than a given designed measurement. Also, a stepped part 16 as the verge shape portion is formed at a position offset to either one of a pair of openings of the bottom hole. The stepped part 16 is punched from the opening side near the position where the stepped part 16 is offset.
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