Press Brake Tonnage Calculator
Press brake tonnage is the force a press needs to make a bend. This gives a rough air-bending figure from the bend length, the material thickness, the die opening and the material's tensile strength.
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How it works
The estimate multiplies 1.42 by the tensile strength, the bend length and the square of the thickness, then divides by the die opening. Enter every length and the strength in any units; they are converted first, and the answer is a force.
This is a rule-of-thumb formula for air bending. It is not a press chart. Real jobs should be checked against the press maker's tonnage table and the tooling data.
Worked example
A 48 in bend in 0.125 in material over a 1 in die needs about 63,900 lbf of press force, using the strength you entered.
Questions
Where do I find the tensile strength?
Material data sheets list it for each grade and temper. Use the value for the exact material, since the same steel family can vary.
Why does thickness matter so much?
Force rises with the square of the thickness, so a sheet a little thicker needs much more force.
Does this cover bottoming or coining?
No. Those methods need much more force and their own formulas. This shows air bending only.
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