How this calculator works
The cut surface area is perimeter times thickness. Multiplying by shear strength gives ideal peak cutting force for a flat punch. Tool wear, punch shear, clearance, stripping force and press energy are outside this estimate. Material grade and condition strongly affect shear strength.
Formula
F = P t tau; P = F/(t tau); t = F/(P tau); tau = F/(P t). Use metres and Pa to obtain newtons.
Worked example
A 100 mm perimeter through 2 mm sheet at 300 MPa shear strength requires 0.1 x 0.002 x 300000000 = 60000 N, or 60 kN.
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Frequently asked questions
Do I use tensile strength?
Use shear strength from an appropriate material reference. A fixed fraction of tensile strength is only an approximation and is not assumed here.
What if several holes are punched together?
Add all perimeters cutting simultaneously.
Is the force the required press rating?
It is only nominal cutting force. The press and tooling supplier must account for stripping, energy and operating margins.