What is Punching Force?
Punching force is the amount of force that a punch press must exert to shear a hole in a material. It is a critical calculation to ensure the selected press has enough capacity for the job and to prevent damage to the tooling or machine.
The calculation is based on the formula: Force = Perimeter × Thickness × Shear Strength. The perimeter is the total length of the cut, the thickness is the thickness of the material, and the shear strength is a property of the material indicating its resistance to being cut in this way.
Approximate Shear Strength of Common Materials
| Material | Shear Strength (PSI) |
|---|---|
| Mild Steel (A36) | 45 |
| Stainless Steel (304) | 70 |
| Aluminum (6061-T6) | 30 |
| Copper | 25 |
How to Use the Calculator
- Select the material you intend to punch from the list.
- Enter the thickness of the material in inches.
- Choose the shape of the hole you want to punch.
- Enter the dimensions of the hole (diameter, side length, etc.).
- Click "Calculate Force" to see the required force in US Tons.
Frequently Asked Questions
What is "Shear Strength"?
Shear strength is a material's ability to resist forces that cause its internal structure to slide against itself. In punching, it's the force required to cut or "shear" the slug out of the parent material. Different materials have vastly different shear strengths.
Does this calculator account for die clearance?
No. This calculator provides the fundamental force required for shearing. Proper die clearance (the gap between the punch and the die) is critical for reducing force, improving hole quality, and increasing tool life. However, this formula provides the necessary baseline for machine selection.