| 摘要 |
PROBLEM TO BE SOLVED: To prevent a punched scrap from going up by providing an inner peripheral wall forming a through hole of a die, with at least one protrusion extended from the upper end to the lower end of the through hole. SOLUTION: Three protrusions 16a are formed at the inner peripheral wall of a die 15 integrally with the die 15 at equal spaces linearly from the upper end to the lower end of a through hole. The protrusions 16a have triangular cross section and protrude toward a center axis L. A punched scrap of a bored plate 11 punched by a punch 13 enters the through hole 16 as the punch 13 is fitted into the through hole 16, and abuts on protrusions 16a since the protrusions 16a bite into it at the side face. This punched scrap remains in the through hole 16 and never goes up in the state of abutting on the protrusions 16a even if the punch 13 moves up. Boring work to the bored plates can therefore be continuously performed, and the generation of an off-specification product can be prevented.
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