Sheet-metal cutting often separates material by forcing it between a punch and die rather than by forming a machining chip.

In blanking, the cut-out piece is the desired part. In punching, the removed slug is waste and the remaining sheet contains the desired hole or opening.

A small clearance is intentionally left between punch and die. The sheet first deforms elastically and plastically, then cracks initiate from the tool edges and propagate until separation occurs.

For a cut perimeter $L$, sheet thickness $t$ and an effective shear strength $\tau_s$, a simple peak-force estimate is

$$F\approx L t\tau_s.$$

If a circular hole of diameter $20$ mm is punched through $2$ mm sheet with $\tau_s=250\ \mathrm{MPa}$,

$$L=\pi(20)\approx62.8\ \mathrm{mm},$$

and

$$F\approx62.8\times2\times250\approx31{,}400\ \mathrm N=31.4\ \mathrm{kN}.$$

Clearance affects edge quality, force, tool wear and burr formation. Too little or too much clearance can worsen the cut even though the nominal geometry is unchanged.

Blank layout also affects material utilization. Nesting parts efficiently in sheet can reduce scrap without changing the part design itself.