| 摘要 |
A machine for punching holes in sheet metal has a punch roller carrying a plurality of punches and a back up roller having a groove therein which has a bottom at a predetermined depth in the back up roller. Its method of use is to run sheet metal through the nip between the two rollers so that the punches punch out slugs of metal so that a point on each slug bears against the bottom of the groove which acts as a pivot point on which the slug pivots to cause the slug to be completely freed from the parent metal by the further action of the punch.
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