Calculate preliminary blanking or piercing force from cut perimeter, sheet thickness and material shear strength.
| Parameter | Value | Formula / Basis | Purpose |
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A common preliminary estimate for blanking and piercing force is based on the sheared area multiplied by the material's shear strength.
Where F is cutting force, L is the total cut perimeter, t is sheet thickness and τ is material shear strength.
When perimeter and thickness are entered in millimetres and shear strength in MPa, the resulting force is obtained in newtons:
Therefore:
The calculator also reports the theoretical sheared area represented by the perimeter multiplied by sheet thickness:
This is not the plan-view area of the blank or hole. It represents the approximate vertical shear area along the cutting perimeter.
Real punching operations can experience peak loads that differ from a simple theoretical calculation. The calculator therefore provides optional planning adjustments.
The machine-capacity estimate additionally accounts for the selected press/process efficiency and machine margin:
These inputs are planning factors rather than universal standards.
The required cutting force helps determine whether a press or punching machine has sufficient capacity for a proposed operation.
The same basic cutting-force relationship can be used for both blanking and piercing. The main difference is which portion of the material is retained.
In blanking, the cut-out blank is generally the useful component. In piercing, the hole is generally the useful feature and the removed slug becomes scrap.
For multiple simultaneous cuts, use the combined active cut perimeter when estimating total cutting force.
A calculated cutting force should not automatically be treated as the exact press rating required. Press selection also depends on stroke, force curve, shut height, tooling, speed, energy and the location in the machine stroke where peak force occurs.
How is punching force calculated?
A common preliminary equation is F = L × t × τ, where L is cut perimeter, t is sheet thickness and τ is material shear strength.
Can I use this for piercing holes?
Yes. Enter the total perimeter of the holes being pierced.
Can I use this for blanking?
Yes. Enter the perimeter of the blank being cut.
What happens if several holes are punched at once?
Their active cut perimeters should be added together when estimating simultaneous cutting force.
Is punching force the same as press tonnage?
No. Punching force is a load, while press tonnage is a machine-capacity rating. This calculator converts the estimated force into an approximate metric tonne-force value for screening.
Why is shear strength used instead of tensile strength?
Punching is a shearing operation, so shear strength is a more directly relevant material property for the simplified cutting-force equation.
Does punch clearance affect force?
Yes. Clearance affects the shearing process and can influence peak force, fracture behavior, tool wear and cut quality.
Can this calculator select a punching machine?
It provides a preliminary required capacity estimate. Actual machine selection requires checking the manufacturer's force-versus-stroke characteristics and the complete tooling/process requirements.