What Piercing means
Piercing cuts a hole by driving a punch through the sheet into a matching die; the punched material leaves as a slug. It is the workhorse hole-making operation in stamping and punching — a single stroke, a hole the exact size of the punch, repeatable across thousands of hits.
Why it matters on the shop floor
Two design consequences follow. The smallest hole a punch can make is limited by punch strength — beyond a certain slenderness the punch snaps, which is why very small holes move to drilling. And the hole edge carries the punch geometry: a slight burnish on the top face and a fracture band below, which matters on sealing faces and threaded features. Threaded holes in thin sheet usually go to extruded (flow) taps or PEM inserts rather than direct piercing.
What to remember
- Minimum pierced hole ≈ 1 × material thickness for most materials — below that, drill.
- Slug management is real: every pierce produces a slug that has to clear the die.
- Extruded holes (threaded in thin sheet) are a forming operation, not a piercing one.