Nine out of ten kinked aluminium tubes we’re asked to diagnose at Aluminium Tubes failed for the same reason: someone bent a T6 tube to a radius only an annealed temper can survive. The alloy was right, the bender was fine — the aluminium tube bending radius chart was missing from the workshop wall.
This page is that chart. Below you’ll find minimum bend radii for every common alloy and temper — 3003, 5052, 5083, 6061, 6063 — expressed the way benders actually work (multiples of tube OD, to centerline), plus springback values for each temper, the wall-thickness rule that decides when you need a mandrel, and the five mistakes that scrap tubes even when the radius is right.
Print the table. Tape it above the bender. Scrap rate drops this week.
Minimum bend radius is the tightest curve an aluminium tube can be bent to without kinking, cracking, or excessive flattening — measured to the bend’s centerline (CLR) and expressed in multiples of tube outside diameter (OD). It depends on alloy, temper, and the tube’s diameter-to-wall ratio: softer tempers like 3003-O bend to ~1.5×OD, while hard 6061-T6 needs 3×OD or more.
The Chart: Minimum Bend Radius by Alloy & Temper
Radii are to centerline (CLR), for rotary-draw bending of typical wall tubes (D/t ≤ 20). Thin walls need more — see the wall-factor rule below the table.
| Alloy-Temper | Min Bend Radius (×OD) | Springback | Bending Notes |
|---|---|---|---|
| 3003-O | 1 – 1.5× | Low (~1–2°) | The tightest bender in aluminium — coils, HVAC circuits |
| 3003-H14 | 2× | Low–moderate | Still forgiving; slight radius penalty for the strength gain |
| 5052-O | 1.5× | Low | Best strength-to-bendability combination in the family |
| 5052-H32 | 2 – 2.5× | Moderate (~2–3°) | Fuel and refrigerant lines standard |
| 5083-O/H111 | 2 – 2.5× | Moderate | Marine circuits; watch higher forces vs 5052 |
| 6063-T5 | 2.5 – 3× | Moderate–high | Architectural bends; polish dies to protect finish |
| 6061-O | 2× | Low | Anneal-bend-then-age route when T6 radius won’t fit |
| 6061-T4 | 2.5 – 3× | Moderate | The smart middle path — bend in T4, artificially age to T6 after |
| 6061-T6 | 3 – 4× | High (3–5°) | Below 3×OD expect kinks; mandrel strongly advised |
| 6082-T6 | 3 – 4× | High | Treat exactly like 6061-T6, slightly stiffer |
| 2024-T3 / 7075-T6 | 4 – 5×+ | Very high | Aerospace grades resist bending — design around it or anneal |
Values are workshop-safe starting points consistent with Aluminum Association forming guidance and ASM Handbook forming data; your die set, lubrication, and wall factor shift the achievable limit. When a bend is critical, test one tube first — cheaper than scrapping ten.
How to Use This Bending Radius Chart (4 Steps)
The key steps to reading a minimum bend radius from the chart are:
- Identify alloy AND temper from the Mill Test Certificate — not from memory. “6061” tells you nothing until you know if it’s O, T4, or T6; the radius triples across those tempers.
- Multiply your tube OD by the chart factor. Example: 25mm OD in 6061-T6 → 3×25 = 75mm minimum centerline radius. Your bend die’s CLR must be 75mm or larger.
- Check the wall factor (D/t). Divide OD by wall thickness. Under 20: chart values hold. 20–30: add half a diameter to the radius or fit a mandrel. Over 30: mandrel and wiper die are mandatory at any radius.
- Add springback compensation. Overbend by the chart’s springback figure — a 90° bend in 6061-T6 is formed to roughly 93–95° so it relaxes back to 90°.
Why Temper Changes Everything: The Metallurgy in 60 Seconds
Bending is controlled stretching — the outer wall of the bend elongates while the inner wall compresses. Elongation capacity is what tempers trade away for strength.
Annealed (O) tempers stretch 25–30% before cracking, so they wrap tight radii happily. Work through cold-worked H tempers and the window narrows. Heat-treated T6 sits at the far end: roughly 8–12% elongation — strong precisely because its microstructure resists deformation, which is exactly what a tight bend demands. That’s why the main difference between bending 3003-O and 6061-T6 is a 2–3× larger radius requirement plus double the springback — the chart is metallurgy translated into die sizes.
The T4 Trick Experienced Shops Use
In practice, when a design needs T6 strength AND a radius T6 can’t survive, fabricators order 6061 in T4 temper, bend at the friendlier 2.5×OD limit, then artificially age the finished part to T6 properties (approximately 8 hours at 175°C). You get the tight bend and the final strength — a route we regularly arrange for OEM customers at Aluminium Tubes ordering drawn tubes for hydraulic assemblies.
The Anneal-and-Rebend Rescue
Already own T6 tube that must take a tight bend? Localised annealing (heat to ~350–400°C, cool) softens the bend zone — but the annealed zone stays soft unless the whole part is re-heat-treated. Acceptable on brackets; never on pressure lines.
Wall Thickness: The Factor the Alloy Chart Can’t See
Two 6061-T6 tubes, same 25mm OD, same 75mm die: the 3mm-wall tube bends clean while the 1mm-wall tube collapses. The difference is the D/t ratio — 8.3 versus 25.
Thin walls buckle inward before the material’s elongation limit is ever reached. The fixes, in escalating order: tighter die fit → internal mandrel (plug or ball type) → wiper die against wrinkles → for one-off jobs, the old packed-sand or low-melt-alloy fill trick. Our step-by-step bending guide covers each method with setup details — this chart tells you the radius; that guide shows you the hands.
5 Mistakes That Scrap Tubes Even at the Right Radius
- Reading OD radius as centerline radius. Die catalogues quote CLR; drawings sometimes dimension to the inside of the bend. A 75mm CLR is not a 75mm inside radius — confirm which one the drawing means before cutting anything.
- Trusting the alloy, ignoring the temper. The single biggest cause of Monday-morning kinks. Certificate first, chart second, bend third.
- No lubrication on draw bends. Dry dies gall aluminium, galled dies score tubes, scored tubes crack at the score. A film of bending lube is the cheapest insurance in the shop.
- Bending welded tube on the seam. If you must bend welded tube, rotate the seam to the neutral axis (side of the bend) — never the outer stretch zone.
- Springback guessing on multi-bend parts. Errors compound across bends; a 3° miss on bend one becomes a part that won’t fit at bend four. Test-bend, measure, program the compensation.
Frequently Asked Questions
What is the minimum bend radius for 6061-T6 aluminium tube?
Plan on 3× the tube’s outside diameter to centerline as the safe minimum, extending to 4×OD for thin walls (D/t over 20). A 25mm OD 6061-T6 tube therefore needs a 75–100mm CLR die. Tighter bends demand a mandrel, or switching to T4 temper and ageing after forming.
Which aluminium alloy bends the easiest?
3003 in O temper bends tightest — down to roughly 1–1.5× its diameter — which is why refrigeration coils and HVAC circuits use it. 5052-O follows closely at ~1.5×OD while offering nearly double the strength, making it the best all-round choice for formed tube work.
What is CLR in tube bending?
CLR means centerline radius — the radius measured from the bend’s center point to the middle of the tube, not to its inner or outer wall. Bend dies are specified by CLR, and every value in this chart is a CLR figure. Inside radius = CLR minus half the OD.
How much springback does aluminium tube have?
It scales with temper strength: roughly 1–2° for annealed tempers, 2–3° for H32-type work-hardened tempers, and 3–5° for 6061-T6/6082-T6 on a 90° bend. Compensate by overbending, and always verify on a test piece — die condition and wall thickness shift the exact figure.
Can you bend aluminium tube without a bender?
Small, soft tubes (3003/5052-O under ~12mm) can be hand-bent around a former, ideally packed with sand to resist kinking. Anything harder, larger, or thin-walled needs at least a spring bender, and T6 tempers realistically need a rotary-draw bender with the correct CLR die.
Is it better to bend aluminium hot or cold?
Cold, in the right temper, for almost all production work — heat above ~200°C permanently degrades T6 properties. The professional routes around a too-tight radius are ordering T4 and ageing after bending, or full local annealing followed by re-heat-treatment where the application allows.
Get Tube That’s Ordered to Bend
Half of bending success is purchased, not formed: the right temper for your radius, the right wall for your D/t, seamless where the bend is critical. Aluminium Tubes supplies seamless, drawn, and coiled tubes in every alloy and temper on this aluminium tube bending radius chart — including bend-friendly O and T4 tempers most stockists don’t hold — with EN 10204 3.1 certificates stating the temper you’ll actually be bending.
Send us your bend radius, OD, and wall — and we’ll confirm the temper that forms it right the first time.
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