In stamping, every operation falls into one of two families based on how the material deforms. Separation operations—blanking, piercing, and shearing—force the sheet to fracture along a closed contour. The whole game here is blanking clearance. As a rule of thumb on the floor: for soft materials, run 5%–8% of sheet thickness; for hard materials, 10%–12%. Go under the clearance and you get tall burrs plus accelerated die wear on the cutting edges; go over it and the collapse zone (rollover) grows, hurting part accuracy and stack-up in assembly. When we set up a piercing die, we always verify clearance per side, not total, and check punch-to-die alignment before the first stroke.
Forming operations—bending, drawing, flanging—plastically deform the sheet without fracturing it. Bending lives or dies on springback: calculate it, then compensate in the tool angle or add a bottoming/coining step rather than chasing parts at the press. Drawing is governed by the limit draw ratio; for low-carbon steel the first draw coefficient should generally not drop below 0.5. Push past that and you get fracture at the punch nose or severe thinning in the wall. In practice we confirm the draw ratio at the process-planning stage, before blank size and die layout are frozen, because a wrong first-draw coefficient means re-cutting the die—expensive and slow.
Keeping these two categories straight is what keeps nesting and operation sequencing clean. Separation steps set the blank outline and hole positions; forming steps follow in an order that respects material flow and avoids distorting previously cut features. Get the classification right at the process sheet, and the die design, tonnage selection, and tryout all fall into line. For more mold sourcing and stamping die information, visit MoldSo at www.moldso.com.