Air bending force per metre and total tonnes for common bend lengths, in mild steel, stainless and aluminium — plus a full die-by-thickness grid so you can see what opening the die up actually saves. Every figure is generated from the same formula as the calculator, so nothing here can contradict it.
Using the usual V-die for each thickness (roughly 6–8 × t). Columns to the right are total tonnes for that bend length in one hit.
| Thickness | Usual V-die | kN/m | t/m | 1 m | 2 m | 2.5 m | 3 m |
|---|---|---|---|---|---|---|---|
| 1 mm | V6 | 97 | 9.9 | 9.9 | 19.8 | 24.7 | 29.7 |
| 1.5 mm | V10 | 131 | 13.4 | 13.4 | 26.7 | 33.4 | 40.1 |
| 2 mm | V12 | 194 | 19.8 | 19.8 | 39.6 | 49.5 | 59.3 |
| 2.5 mm | V16 | 227 | 23.2 | 23.2 | 46.4 | 58.0 | 69.5 |
| 3 mm | V22 | 238 | 24.3 | 24.3 | 48.6 | 60.7 | 72.8 |
| 4 mm | V26 | 358 | 36.5 | 36.5 | 73.0 | 91.3 | 109.6 |
| 5 mm | V32 | 455 | 46.4 | 46.4 | 92.7 | 115.9 | 139.1 |
| 6 mm | V40 | 524 | 53.4 | 53.4 | 106.8 | 133.5 | 160.2 |
| 8 mm | V50 | 745 | 76.0 | 76.0 | 151.9 | 189.9 | 227.9 |
| 10 mm | V63 | 924 | 94.2 | 94.2 | 188.4 | 235.5 | 282.6 |
| 12 mm | V80 | 1048 | 106.8 | 106.8 | 213.7 | 267.1 | 320.5 |
| Thickness | Usual V-die | kN/m | t/m | 1 m | 2 m | 2.5 m | 3 m |
|---|---|---|---|---|---|---|---|
| 1 mm | V6 | 116 | 11.8 | 11.8 | 23.6 | 29.6 | 35.5 |
| 1.5 mm | V10 | 157 | 16.0 | 16.0 | 31.9 | 39.9 | 47.9 |
| 2 mm | V12 | 232 | 23.6 | 23.6 | 47.3 | 59.1 | 70.9 |
| 2.5 mm | V16 | 272 | 27.7 | 27.7 | 55.4 | 69.3 | 83.1 |
| 3 mm | V22 | 285 | 29.0 | 29.0 | 58.0 | 72.5 | 87.0 |
| 4 mm | V26 | 428 | 43.6 | 43.6 | 87.3 | 109.1 | 130.9 |
| 5 mm | V32 | 544 | 55.4 | 55.4 | 110.8 | 138.5 | 166.2 |
| 6 mm | V40 | 626 | 63.8 | 63.8 | 127.7 | 159.6 | 191.5 |
| 8 mm | V50 | 891 | 90.8 | 90.8 | 181.6 | 227.0 | 272.4 |
| 10 mm | V63 | 1104 | 112.6 | 112.6 | 225.2 | 281.5 | 337.8 |
| 12 mm | V80 | 1252 | 127.7 | 127.7 | 255.3 | 319.2 | 383.0 |
| Thickness | Usual V-die | kN/m | t/m | 1 m | 2 m | 2.5 m | 3 m |
|---|---|---|---|---|---|---|---|
| 1 mm | V6 | 142 | 14.5 | 14.5 | 29.0 | 36.2 | 43.4 |
| 1.5 mm | V10 | 192 | 19.5 | 19.5 | 39.1 | 48.9 | 58.6 |
| 2 mm | V12 | 284 | 29.0 | 29.0 | 57.9 | 72.4 | 86.9 |
| 2.5 mm | V16 | 333 | 33.9 | 33.9 | 67.9 | 84.8 | 101.8 |
| 3 mm | V22 | 349 | 35.5 | 35.5 | 71.1 | 88.8 | 106.6 |
| 4 mm | V26 | 524 | 53.4 | 53.4 | 106.9 | 133.6 | 160.3 |
| 5 mm | V32 | 666 | 67.9 | 67.9 | 135.7 | 169.6 | 203.6 |
| 6 mm | V40 | 767 | 78.2 | 78.2 | 156.3 | 195.4 | 234.5 |
| 8 mm | V50 | 1091 | 111.2 | 111.2 | 222.3 | 277.9 | 333.5 |
| 10 mm | V63 | 1352 | 137.9 | 137.9 | 275.7 | 344.6 | 413.6 |
| 12 mm | V80 | 1534 | 156.3 | 156.3 | 312.7 | 390.8 | 469.0 |
| Thickness | Usual V-die | kN/m | t/m | 1 m | 2 m | 2.5 m | 3 m |
|---|---|---|---|---|---|---|---|
| 1 mm | V6 | 73 | 7.5 | 7.5 | 15.0 | 18.7 | 22.4 |
| 1.5 mm | V10 | 99 | 10.1 | 10.1 | 20.2 | 25.2 | 30.3 |
| 2 mm | V12 | 147 | 15.0 | 15.0 | 29.9 | 37.4 | 44.9 |
| 2.5 mm | V16 | 172 | 17.5 | 17.5 | 35.1 | 43.8 | 52.6 |
| 3 mm | V22 | 180 | 18.4 | 18.4 | 36.7 | 45.9 | 55.1 |
| 4 mm | V26 | 271 | 27.6 | 27.6 | 55.2 | 69.0 | 82.8 |
| 5 mm | V32 | 344 | 35.1 | 35.1 | 70.1 | 87.6 | 105.2 |
| 6 mm | V40 | 396 | 40.4 | 40.4 | 80.8 | 101.0 | 121.2 |
| 8 mm | V50 | 563 | 57.4 | 57.4 | 114.9 | 143.6 | 172.3 |
| 10 mm | V63 | 699 | 71.2 | 71.2 | 142.5 | 178.1 | 213.7 |
| 12 mm | V80 | 792 | 80.8 | 80.8 | 161.5 | 201.9 | 242.3 |
Bottoming needs roughly 3–5 × these figures and coining 10 × or more, so a chart figure that looks comfortable can still overload a machine if the job is being bottomed. Run your own numbers →
The same bend over a wider die needs less force. Figures in white are inside the normal 6–8 × t working band; grey figures are usable but tight or wide; dashes are outside anything sensible.
| Thickness | V6 | V10 | V12 | V16 | V22 | V26 | V32 | V40 | V50 | V63 | V80 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 mm | 9.9 | 5.9 | 4.9 | 3.7 | — | — | — | — | — | — | — |
| 1.5 mm | 22.3 | 13.4 | 11.1 | 8.3 | 6.1 | — | — | — | — | — | — |
| 2 mm | — | 23.7 | 19.8 | 14.8 | 10.8 | 9.1 | 7.4 | — | — | — | — |
| 2.5 mm | — | 37.1 | 30.9 | 23.2 | 16.9 | 14.3 | 11.6 | 9.3 | — | — | — |
| 3 mm | — | — | 44.5 | 33.4 | 24.3 | 20.5 | 16.7 | 13.4 | — | — | — |
| 4 mm | — | — | — | 59.3 | 43.2 | 36.5 | 29.7 | 23.7 | 19.0 | 15.1 | — |
| 5 mm | — | — | — | — | 67.4 | 57.1 | 46.4 | 37.1 | 29.7 | 23.6 | 18.5 |
| 6 mm | — | — | — | — | — | 82.2 | 66.8 | 53.4 | 42.7 | 33.9 | 26.7 |
| 8 mm | — | — | — | — | — | — | 118.7 | 95.0 | 76.0 | 60.3 | 47.5 |
| 10 mm | — | — | — | — | — | — | — | 148.4 | 118.7 | 94.2 | 74.2 |
| 12 mm | — | — | — | — | — | — | — | — | 170.9 | 135.7 | 106.8 |
Read along a row: 6 mm mild steel takes about 26 t/m over a V40, but around 41 t/m over a V26 — a 55% jump in force for a tighter radius. Opening the die is the cheapest tonnage saving there is, as long as the drawing tolerates the larger radius.
Most published tonnage charts print a single die opening per thickness and a single steel grade, then get quoted as if they were universal. Force is proportional to tensile strength and inversely proportional to die opening, so the same 3 mm bend can legitimately read 19 t/m or 35 t/m depending on those two choices. Check which die and which grade a chart assumes before you trust it — on this page it is stated in every heading.
Doubling the thickness roughly quadruples the force before you allow for the wider die you would normally move to. That is why 3 mm feels easy and 8 mm suddenly does not.
The machine's rated tonnage is one ceiling; the punches and dies have another, quoted per metre in the supplier's catalogue — commonly around 80 t/m for standard precision-ground sections, more for heavy styles. Exceed it and the tooling fails before the sheet does. Short bends are where this bites: 30 tonnes over 2 m is routine, the same 30 tonnes over a 150 mm punch is 200 t/m and will damage tools.
Mill certificates commonly show tensile strength well above the grade minimum, and a chart built on the nominal figure understates the force you will actually need. Treat every number here as an estimate within roughly 10–15%, then leave margin.
About 24 t/m air bending over a V22 die at Rm 410 — so roughly 60 tonnes across a 2.5 m bend. Over a V16 the same bend needs about 33 t/m.
Around 26 t/m over a V40 in mild steel, so about 79 tonnes for a full 3 m bend in air. Allow headroom: a 100 tonne machine handles it comfortably, a 90 tonne machine is running at nearly 90% of capacity with no margin for stronger-than-nominal material.
Different assumed die opening, different steel grade, or a different empirical constant (1.33, 1.42 and 1.65 are all in circulation). This page uses 1.42, the constant most press brake tooling manufacturers publish for air bending.
No. Multiply by roughly 3–5 for bottoming and 10 or more for coining. Those multipliers are rough and move with punch radius and how hard the machine is set to press.
Please read this before using any figure from this page in production.
Every output here is an indicative calculation produced from the values you enter. Real results vary with springback, grain direction, tooling condition and geometry, friction and lubrication, machine calibration and load distribution, temperature, and batch-to-batch variation in material properties. Actual tensile strength commonly differs from the nominal figures listed. Treat these numbers as a starting point to be proven on a test piece — never as a verified value for a production run, a load calculation, or a safety-critical component.
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