| 摘要 |
PROBLEM TO BE SOLVED: To provide a circular punch for piercing, which circular punch can reduce a fear of generating cracks on the tip end surface made of superabrasives and ceramics to be very small degree, and can stably achieve a long life cycle. SOLUTION: The tip end surface of the punch 1 to be brought into contact with a workpiece is formed from a superabrasive layer or ceramics so as to form a tapered surface 13. In a shearing operation, the stress concentrates at the cutting edge on the periphery of the tip end surface of the punch 1. However, the stress concentration can be relaxed because the tip end surface is the tapered surface. COPYRIGHT: (C)2007,JPO&INPIT
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