3 mm 5052-H32 aluminium bend allowance and bend deduction
At a 90° bend with an inside radius of one thickness (3.00 mm / 0.1181 in) and K = 0.40, 3 mm 5052-H32 aluminium (3 mm / 0.1181 in) has a bend allowance of 6.60 mm (0.2597 in) and a bend deduction of 5.40 mm (0.2127 in).
| Bend angle | Included angle | BA (mm) | BD (mm) | BA (in) | BD (in) |
|---|---|---|---|---|---|
| 30° | 150° | 2.20 | 1.02 | 0.0866 | 0.0400 |
| 45° | 135° | 3.30 | 1.67 | 0.1299 | 0.0658 |
| 60° | 120° | 4.40 | 2.53 | 0.1732 | 0.0996 |
| 90° | 90° | 6.60 | 5.40 | 0.2597 | 0.2127 |
| 120° | 60° | 8.80 | 11.99 | 0.3463 | 0.4720 |
| 135° | 45° | 9.90 | 19.07 | 0.3896 | 0.7510 |
| Inside radius | R / T | K-factor | BA (mm) | BD (mm) | BA (in) | BD (in) |
|---|---|---|---|---|---|---|
| 1.50 mm | 0.5 | 0.33 | 3.91 | 5.09 | 0.1540 | 0.2003 |
| 3.00 mm | 1 | 0.40 | 6.60 | 5.40 | 0.2597 | 0.2127 |
| 4.50 mm | 1.5 | 0.40 | 8.95 | 6.05 | 0.3525 | 0.2380 |
| 6.00 mm | 2 | 0.40 | 11.31 | 6.69 | 0.4453 | 0.2634 |
| 9.00 mm | 3 | 0.40 | 16.02 | 7.98 | 0.6308 | 0.3141 |
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 0.33 below R = T, 0.40 from T to 3T, 0.50 above 3T for 5052-H32 aluminium). 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 (24.00 mm / 0.9449 in) is the usual starting point. In air bending the inside radius forms at roughly 13–15% of the die opening for 5052-H32 aluminium, 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 5052-H32 aluminium at modest radii is typically about 1.5–3°, increasing as R/T grows; overbend to compensate. It changes the angle, not the bend allowance calculation.
5052-H32 is the usual choice for bent aluminium parts: about 1 × T is a common minimum for thin 5052-H32 sheet; thicker plate needs a larger radius, so check your supplier's bend data. Bending across the rolling direction (grain) gives the best results, especially on thicker sheet.
FAQ
What is the bend deduction for 3 mm 5052-H32 aluminium at 90°?
With R = T (3.00 mm / 0.1181 in) and K = 0.40, the bend deduction is 5.40 mm (0.2127 in). For a part with two 50 mm flanges measured to the outside, the flat blank is 50 mm + 50 mm − 5.40 mm = 94.60 mm.
What K-factor should I use for 3 mm 5052-H32 aluminium?
For air bending 5052-H32 aluminium at R = T, a K-factor of about 0.40 is a typical starting value; below R = T it drops to about 0.33, and above 3 × T it approaches 0.50. Real values depend on tooling and material lot, so confirm with a test bend.
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: 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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