Sheet metal / sourced air-bending estimate
Estimate 90° V-die air-bending force, compare two published calculation models, and check the result against entered machine and tooling ratings.
Both estimates remain visible in the output.
Use material UTS, not yield strength. Mild-steel reference condition is about 410 MPa / 60 ksi.
Force changes with the square of actual thickness.
The opening affects force, natural radius, minimum flange, marking, and tooling selection.
Enter only the simultaneously formed length.
Use the applicable capacity for this bend length and load position, not just the machine nameplate.
Use the lowest allowable rating in the punch, die, holder, and adapter stack.
Formula transparency
US tons = [(575 × t² / V) / 12] × L × (UTS / 60,000)Dimensions are inches and UTS is psi. Air-bending method and standard tooling factors are 1. Converted to SI, the coefficient is approximately 1.59722 when force is kN, UTS is MPa, length is m, and t and V are mm.
F(kN) = 1.42 × UTS × L(m) × t² / VUTS is N/mm² (numerically equal to MPa); thickness and V opening are mm. It usually returns a lower result than the Bystronic 575 formula for the same inputs.
Natural inside radius ≈ 0.15 × V; minimum flange ≈ 0.70 × VThese are approximate 90° air-bend planning values. Read the actual tooling chart before choosing a punch, die, or flange geometry.
Utilization = required force / entered rating × 100%The tooling check uses force per bend length. A value at or below 100% only means the estimate is within the rating you entered; it does not certify the setup.
Worked example
Primary references: Bystronic — How to calculate press brake tonnage · Wilson Tool — Air Bend Force Chart · WILA — V-opening selection · CINCINNATI — Air-bend load calculator
Implementation: Original MfgWorkbench calculation code, independently checked against the cited formulas and worked example. Last reviewed September 6, 2026.
Press brake FAQ
For a 90-degree V-die air bend, force increases with ultimate tensile strength, bend length, and the square of material thickness, and decreases as the V-die opening becomes wider. This calculator provides the Bystronic 575 model and the common 1.42 metric model so their assumptions are visible.
A common starting point for mild-steel air bending is 6 to 8 times material thickness for thinner sheet, with wider ratios for thicker plate or higher-strength material. The correct opening must also satisfy radius, minimum-flange, marking, force, and tooling requirements.
No. The calculation is restricted to 90-degree air bending. Official references indicate that bottoming and coining can require several times the air-bending force, and the correct multiplier depends on the process and tooling.
Published manufacturer charts and formulas use different coefficients and reference conditions. Showing both sourced models makes that sensitivity visible instead of presenting one coefficient as universally exact.
No. A result within the entered ratings is only a planning check. Verify the press brake load chart, allowable load distribution, tooling rating, setup, material certificate, minimum flange, and manufacturer guidance before production.