18 gauge 5052-H32 aluminium bend allowance and bend deduction
At a 90° bend with an inside radius of one thickness (0.0403 in / 1.02 mm) and K = 0.40, 18 gauge 5052-H32 aluminium (0.0403 in / 1.02 mm) has a bend allowance of 0.0886 in (2.25 mm) and a bend deduction of 0.0726 in (1.84 mm).
| Bend angle | Included angle | BA (in) | BD (in) | BA (mm) | BD (mm) |
|---|---|---|---|---|---|
| 30° | 150° | 0.0295 | 0.0137 | 0.75 | 0.35 |
| 45° | 135° | 0.0443 | 0.0225 | 1.13 | 0.57 |
| 60° | 120° | 0.0591 | 0.0340 | 1.50 | 0.86 |
| 90° | 90° | 0.0886 | 0.0726 | 2.25 | 1.84 |
| 120° | 60° | 0.1182 | 0.1610 | 3.00 | 4.09 |
| 135° | 45° | 0.1329 | 0.2562 | 3.38 | 6.51 |
| Inside radius | R / T | K-factor | BA (in) | BD (in) | BA (mm) | BD (mm) |
|---|---|---|---|---|---|---|
| 0.0202 in | 0.5 | 0.33 | 0.0525 | 0.0684 | 1.33 | 1.74 |
| 0.0403 in | 1 | 0.40 | 0.0886 | 0.0726 | 2.25 | 1.84 |
| 0.0605 in | 1.5 | 0.40 | 0.1203 | 0.0812 | 3.06 | 2.06 |
| 0.0806 in | 2 | 0.40 | 0.1519 | 0.0899 | 3.86 | 2.28 |
| 0.1209 in | 3 | 0.40 | 0.2152 | 0.1072 | 5.47 | 2.72 |
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 (0.3224 in / 8.19 mm) 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.
Aluminium gauges use the Brown & Sharpe (AWG) scale, which is thinner than steel at the same number (18 ga aluminium is 0.0403 in, 18 ga steel 0.0478 in). Most suppliers quote aluminium sheet in decimal inches or millimetres, so confirm the actual thickness.
FAQ
What is the bend deduction for 18 gauge 5052-H32 aluminium at 90°?
With R = T (0.0403 in / 1.02 mm) and K = 0.40, the bend deduction is 0.0726 in (1.84 mm). For a part with two 2 in flanges measured to the outside, the flat blank is 2 in + 2 in − 0.0726 in = 3.9274 in.
What K-factor should I use for 18 gauge 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 18 gauge aluminium the same thickness as 18 gauge steel?
No. Aluminium (aluminum) uses the Brown & Sharpe gauge: 18 ga is 0.0403 in (1.02 mm), while 18 ga steel is 0.0478 in.
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: Brown & Sharpe (AWG) 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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