- Cutting force
- 4.36 tonnes
- In kN
- 42.7 kN
- Cut perimeter
- 62.8 mm
- Press to use (+20%)
- 5.2 tonnes or more
The 20% covers stripping and blunt tools. Shear on the punch or die (angled) lowers the force.
How it is worked out
- Force (N) = cut perimeter (mm) × sheet thickness (mm) × shear strength (N/mm²).
- Shear strength is taken as about 0.8 × the tensile strength of the material.
- The press to use adds 20% for stripping force and tool wear.
Questions
- What force is needed to punch a 20 mm hole in 3 mm mild steel?
- Perimeter 62.8 mm (2.47 inch) × 3 mm (0.118 inch) × about 340 N/mm² ≈ 64 kN, or about 6.5 tonnes. A press of 8 tonnes or more gives a margin.
- How can I reduce the punching force?
- Grind shear on the punch (for piercing) or the die (for blanking), or stagger punches of different lengths so they do not cut at the same moment.
- Why does stainless steel need more force?
- Its shear strength is higher, about 470 N/mm² against about 340 for mild steel, so the same hole needs nearly 40% more force.
See also: Press brake bending force calculator, Bend allowance calculator, and all calculators and references.
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