| 摘要 |
The piercing unit of the present invention is a low-cost device having relatively few parts. The unit comprises a C-frame of cast iron. A hole is drilled from the top of the unit, through the top leg and part way into the lower leg. The bottom of the hole forms a seat for the lower end of the die sleeve. A punch holder slide is machined from tool steel for close-tolerance fit within the hole in the top leg. The slide has an opening extending inwardly from its lower end to receive the punch, and a threaded opening extending inwardly from its upper end to receive a stripper bolt. The punch holder slide abuts a shoulder adjacent to the inner end of the stripper bolt, and thus is backed up in its punching stroke. The punch abuts the threaded inner end of the stripper bolt and is thereby backed up in its punching stroke. Dog point set screws hold the punch assembled with the punch holder slide as the punch is being stripped from the steel it has just pierced.
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