Press brake tonnage calculator
Air bending force scales with the square of the thickness and inversely with the die opening. Choosing a wider die is the cheapest way to cut tonnage.
MPa
Mild steel 400; stainless 600; aluminium 200.
Force required
21.72tonnes
- Force in kilonewtons
- 213.00
- Force in US tons
- 23.94
- Force per metre of bend
- 213.0 kN/m
- Suggested die opening
- 24.0
- Force with that die
- 213.0 kN
- Natural inside radius
- 3.84
- Minimum flange for this die
- 16.80
Show the working
- Thickness = 3
- Bend length = 1000
- V-die opening = 24
- Tensile strength = 400
- Force per metre of bend = 1.42 * 400 * 3^2 / 24 = 213
- Force in kilonewtons = 213 * 1000 / 1000 = 213
- Force required = 213 / 9.80665 = 21.72
- Force in US tons = 213 * 1000 / 8896.443230521 = 23.9422
- Suggested die opening = 3 * 8 = 24
- Force with that die = 1.42 * 400 * 3^2 / 24 * 1000 / 1000 = 213
- Natural inside radius = 24 * 0.16 = 3.84
- Minimum flange for this die = 24 * 0.7 = 16.8
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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The formula
- force per metre = 1.42 x tensile strength x thickness^2 / die opening
- air bending produces an inside radius of roughly 0.16 x die opening
The 1.42 coefficient is the standard air-bending constant for a 90-degree bend. Bottoming or coining needs several times more force.
A die opening of eight times thickness is the usual starting point for mild steel.