In stamping, the press and die apply external force to sheet, strip, tube, or profile stock to cause plastic deformation or separation, producing parts of the required shape and size. The four common shop-floor operations—blanking, bending, drawing, and forming—all come down to controlling material flow and fracture. Take blanking: the punch-die clearance is typically set at 5%–10% of sheet thickness. Too small a clearance invites secondary shearing and heavy burrs on the fracture face; too large a clearance produces an obvious rollover and loses dimensional accuracy. From a die-building standpoint, clearance is not a number you pick once—it must be matched to material grade, thickness tolerance, and the wear allowance you build into the punch and die inserts, then verified on the tryout press before the tool is signed off.
Force estimation is equally practical. Blanking force is estimated as F = 1.3 × L × t × τ, where L is the shear perimeter, t the sheet thickness, and τ the material shear strength. That result drives press tonnage selection, and we normally leave about 20% margin so the press is not run at full load for long periods—sustained full-load running accelerates clutch, slide, and frame wear and shortens die life. The same discipline applies to bending and drawing: bending force depends on the bend length, thickness, and tensile strength, while drawing force must account for the blank holder load, otherwise the flange wrinkles or the wall tears. In practice, the calculated tonnage should sit inside the press's rated capacity at the working stroke, not just at bottom dead center.
Good stamping dies are built around these numbers, not around guesswork. Clearance, force, and tonnage margins should be documented in the die design sheet and checked against the actual material certificate before cutting steel. For more mold and die sourcing information, visit MoldSo at www.moldso.com.