| 摘要 |
A punch is provided having a novel tooth configuration wherein the tooth has piercing points at the centers of the extreme ends of a rectangular shank with an arcuate surface connecting the two points and with four concave surfaces connecting the sides of the arcuate surface with flat sides of the rectangular shank. The punch has a double action wherein it first pierces the paper and then shears the side walls so that a minimum amount of energy is necessary.
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