11 gauge 304 stainless steel bend allowance and bend deduction
At a 90° bend with an inside radius of one thickness (0.1250 in / 3.18 mm) and K = 0.45, 11 gauge 304 stainless steel (0.1250 in / 3.18 mm) has a bend allowance of 0.2847 in (7.23 mm) and a bend deduction of 0.2153 in (5.47 mm).
| Bend angle | Included angle | BA (in) | BD (in) | BA (mm) | BD (mm) |
|---|---|---|---|---|---|
| 30° | 150° | 0.0949 | 0.0391 | 2.41 | 0.99 |
| 45° | 135° | 0.1424 | 0.0648 | 3.62 | 1.64 |
| 60° | 120° | 0.1898 | 0.0989 | 4.82 | 2.51 |
| 90° | 90° | 0.2847 | 0.2153 | 7.23 | 5.47 |
| 120° | 60° | 0.3796 | 0.4864 | 9.64 | 12.35 |
| 135° | 45° | 0.4271 | 0.7800 | 10.85 | 19.81 |
| Inside radius | R / T | K-factor | BA (in) | BD (in) | BA (mm) | BD (mm) |
|---|---|---|---|---|---|---|
| 0.0625 in | 0.5 | 0.40 | 0.1767 | 0.1983 | 4.49 | 5.04 |
| 0.1250 in | 1 | 0.45 | 0.2847 | 0.2153 | 7.23 | 5.47 |
| 0.1875 in | 1.5 | 0.45 | 0.3829 | 0.2421 | 9.73 | 6.15 |
| 0.2500 in | 2 | 0.45 | 0.4811 | 0.2689 | 12.22 | 6.83 |
| 0.3750 in | 3 | 0.45 | 0.6774 | 0.3226 | 17.21 | 8.19 |
Practical notes
The angle in these formulas is the bend angle — how far the flange turns away from flat. The included angle between the two flanges is 180° minus the bend angle, so a 90° bend is also 90° included, but a 135° bend leaves a 45° included angle.
K-factor values here come from a generic air-bending table that depends on R/T (about 0.40 below R = T, 0.45 from T to 3T, 0.50 above 3T for 304 stainless steel). They are approximations: tooling, die width, grain and temper all shift the neutral axis. Bend a test strip, measure the flanges and back-calculate K before cutting a production run.
A V-die opening of about 8 × T (1.0000 in / 25.40 mm) is the usual starting point. In air bending the inside radius forms at roughly 20–22% of the die opening for 304 stainless steel, so the radius you actually get depends on the die more than the punch — recompute with that radius if it differs from the R = T used above.
Springback for 304 stainless steel at modest radii is typically about 2–4°, increasing as R/T grows; overbend to compensate. It changes the angle, not the bend allowance calculation.
304 stainless needs roughly 1.5–2 times the press force of mild steel of the same thickness and about 1 × T is a common minimum for annealed 304; it work-hardens quickly, so avoid re-bending. Use protective film or urethane tooling if the finish matters.
Many mills supply stainless sheet to the Manufacturers' Standard Gauge nominal (for example 16 ga as 0.0598–0.060 in rather than 0.0625 in). Measure the sheet you have and rework the numbers if it differs.
FAQ
What is the bend deduction for 11 gauge 304 stainless steel at 90°?
With R = T (0.1250 in / 3.18 mm) and K = 0.45, the bend deduction is 0.2153 in (5.47 mm). For a part with two 2 in flanges measured to the outside, the flat blank is 2 in + 2 in − 0.2153 in = 3.7847 in.
What K-factor should I use for 11 gauge 304 stainless steel?
For air bending 304 stainless steel at R = T, a K-factor of about 0.45 is a typical starting value; below R = T it drops to about 0.40, and above 3 × T it approaches 0.50. Real values depend on tooling and material lot, so confirm with a test bend.
How thick is 11 gauge stainless steel?
On the stainless sheet gauge chart, 11 gauge is 0.1250 in (3.18 mm). Some mills supply stainless to the Manufacturers' Standard Gauge nominal instead, so measure your sheet.
Why does 304 stainless steel need more overbend than mild steel?
304 stainless has a higher yield strength and work-hardens as it bends, so it springs back more — typically about 2–4° at modest radii versus about 0.5–2° for mild steel. The bend allowance is unchanged; only the brake setting differs.
Is the angle in the bend allowance formula the bend angle or the included angle?
It is the bend angle, the amount the flange is turned from flat. If your drawing gives the included angle between flanges, use 180° minus that value: a 45° included angle is a 135° bend.
Sources: Stainless steel sheet gauge · Bend allowance formula BA = A·(π/180)·(R + K·T); bend deduction BD = 2·tan(A/2)·(R + T) − BA (Machinery's Handbook, sheet metal bending) · Generic air-bending K-factor table by R/T (approximate)
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