Punch Force Calculator

Estimate the tonnage required to pierce or blank a part from sheet metal using perimeter, thickness, and material shear strength.

Punching shears material along the cut profile. The force the press must supply is the product of how much edge is being cut (the perimeter), how thick the material is, and how strong the material is in shear.

Size the press above the peak force with margin for stripping and friction — adding roughly 20% is a common rule. If the tonnage is too high, grind a shear angle onto the punch or die to spread the cut over the stroke.

Formula: Force = Perimeter × Thickness × Shear Strength

Worked Example

  1. Cut a 2.0 in × 1.0 in rectangle (perimeter = 6.0 in) in 0.060 in cold-rolled steel with ~50,000 psi shear strength.
  2. Force = 6.0 × 0.060 × 50,000 = 18,000 lb = 9.0 tons.
  3. Add ~20% for stripping/friction → size for roughly 11 tons.

Frequently Asked Questions

How is punch force calculated?

Punch force = cut perimeter × material thickness × material shear strength. Add roughly 20% for stripping and friction when sizing a press.

How do I reduce punching tonnage?

Grinding a shear angle onto the punch or die spreads the cut over the stroke, lowering peak tonnage by 25-50%.

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