Oval and elliptical
Stiffer about the major axis than a round tube of the same weight, with a softer visual line. Used for furniture, medical frames, handlebars and ladder rails. See oval aluminium tubing.
Custom tube guide
Custom Aluminium Tube: Special Shapes, Bends, Telescopic and Tapered Tube
A custom aluminium tube is any tube made to your own section, tolerance, length or shape rather than taken from a standard size list: special extruded sections, mandrel-bent tube, nesting telescopic sets, tapered poles and precision drawn tube. Getting it right depends on choosing the right production route for the shape, the right alloy and temper for the forming steps, and tolerances the process can actually hold. This guide walks through each option and how to specify it.
- Routes
- Extruded, drawn, bent, swaged, spun
- Common alloys
- 6061, 6063, 6082, 7075, 5052
- Sections
- Round, oval, D, multi-chamber, tapered
- Standards
- ASTM B221 · B210 · EN 755 · EN 754
When does a tube need to be custom?
Standard round, square and rectangular tubes cover most structural needs. A custom tube earns its cost when it removes parts, machining or assembly steps: an oval section that gives a stiffer frame in one direction, a tube with an integral mounting rail, a multi-chamber section that carries coolant and cables together, or a pre-bent tube that arrives ready to fit.
Aluminium is unusually well suited to this because extrusion dies are relatively inexpensive compared with tooling for steel roll-forming or casting. A new die for a modest hollow section is often a small part of the cost of a production run, and once it exists the same section can be reordered for years. Secondary operations such as bending, swaging, end forming, CNC machining and anodising can then turn the extrusion into a near-finished component.
Metline supplies custom tube in all common alloys, either as cut lengths of a special section or processed to drawing. We do not make finished assemblies or end products; our job is to deliver the aluminium tube, shaped and finished as your drawing requires, with the certification your project needs.
Choosing the production route for your shape
| Route | Best for | Typical limits | Notes |
|---|---|---|---|
| Porthole (bridge-die) extrusion | Shaped hollows: oval, D-shape, teardrop, multi-chamber, tubes with fins or rails | Section fits within the press circle; minimum wall usually about 1 mm and rising with size | Contains longitudinal weld seams that are sound for structural use; check suitability for high-pressure service |
| Seamless extrusion (piercing / mandrel) | Round tube for pressure, hydraulic and critical structural parts | Mainly round sections; thicker walls | No weld seams; specify where codes call for seamless tube |
| Cold drawing | Precision round and simple shapes, thin walls, smooth surface | Tighter OD and wall tolerances than extrusion | Work-hardens the tube; heat-treated after drawing for T6 tempers |
| Bending (rotary draw, roll, stretch) | Elbows, frames, handles, coils | CLR from about 1 × OD with mandrel; larger radii without | Temper and wall thickness decide the tightest radius |
| Swaging, spinning, tapered rolling | Tapered tubes, reduced ends, poles | Taper length and reduction depend on wall and alloy | Often followed by heat treatment |
| Machining and fabrication | Holes, slots, threads, end features, welded tees | To drawing | CNC or press tooling for volume |
The shape on the drawing usually decides the route. If the section is round and must be seamless, you need seamless extruded or drawn tube. If it is not round, or has internal webs, it is almost always a porthole extrusion. The quickest way to an economical design is to send the drawing early so the section can be adjusted for extrusion before the design is frozen. Our guide seamless vs porthole extruded tube explains the difference in more detail.
Special-shaped extruded tube sections
Streamline and teardrop
Aerofoil sections for struts and braces where drag matters, such as light aircraft, drones and sail rigging. Aerospace versions are drawn to dedicated specifications; see streamline tube.
D-section and semicircular
One flat face for mounting or a mating joint and one curved face for appearance. Common in enclosures, lighting and handrails.
Triangular, trapezoidal and sector
Polygonal hollows for truss chords, telescopic mechanisms and segments that assemble into a larger round shape.
Multi-chamber (multi-port)
Two or more hollows in one section, for separating fluids, adding stiffness, or carrying cables beside coolant. Microchannel tube is the extreme case.
Tube with integral features
Round or square tube with T-slots, fins, screw bosses, keyways or splines extruded in, which removes machining and fastening.
Inside-shaped round tube
Round outside with a hex, square, splined or grooved bore for anti-rotation or sliding fits, and the reverse: round bore, shaped outside.
Hex and square-round
Hexagonal tube for spanner flats and fittings; see aluminium hex tube.
Finned and cooling tube
External or internal fins that increase surface area for heat transfer, for heat exchangers and LED or electronics cooling.
Design tips for extruded hollows: keep wall thickness as uniform as possible, because thick and thin walls next to each other cool at different rates and distort; add generous radii (0.5 mm or more) at internal corners; avoid long, unsupported thin webs; and remember that symmetrical sections extrude straighter and faster than lopsided ones.
Bent and elbow aluminium tube
Bent tube is ordered for frames, handles, rails, ducting, fuel and coolant lines and coils. Three methods cover most work. Rotary-draw bending, with a mandrel inside the tube, produces tight, accurate bends with little ovality and is the norm for small to medium tubes. Roll bending produces large radii and arcs. Stretch bending pulls the tube over a form block and is used for long, gentle curves on profiles and large frames.
| Factor | Effect on bending | Practical guidance |
|---|---|---|
| Temper | Soft tempers (O, T4, H32) bend far more easily than T6 | Bend in O or T4 and age to T6 afterwards for tight radii in 6061 |
| Wall-to-diameter ratio | Thin walls wrinkle on the inside and thin on the outside | Use a mandrel and wiper die when the wall is under about 6 % of OD |
| Centreline radius (CLR) | Tighter radii raise strain and ovality | About 1 – 1.5 × OD with mandrel tooling; 2 – 3 × OD or more without |
| Alloy | 6063 and 5052 bend more easily than 6061-T6, 6082-T6 or 7075 | Choose the most formable alloy that meets strength needs |
| Springback | Aluminium springs back more than steel | Tooling is compensated; specify the finished angle, not the tool angle |
On the drawing, give bend angles, CLR, distances between bends (straight lengths of at least about 1.5 × OD between bends make tooling simpler), allowable ovality and wall thinning, and which ends are datum points. Read more in bent aluminium tubing and, for large-diameter fittings, aluminium elbows.
Telescopic (nesting) aluminium tube
Telescopic tube sets slide one inside another to give adjustable length: tripods, camera and survey poles, antenna and mast sections, tent poles, trekking poles, cleaning poles, medical stands and industrial supports. They can be round, square, rectangular or oval, and often include a groove or key to stop rotation.
The critical number is the clearance between the outside of the inner tube and the bore of the outer tube. Too tight and the tubes jam after anodising or in dust and cold; too loose and the assembly rattles and bends at each joint. Because extruded tube tolerances can be wider than the clearance you want, precision telescopic sets are often drawn tube, or extruded and then sized, with the anodic coating thickness (about 10 – 25 µm per surface) included in the fit calculation.
| Typical use | Common alloys and tempers | Why |
|---|---|---|
| Trekking, tent and outdoor poles | 7075-T6, 7001, 6061-T6 | High strength-to-weight for thin walls |
| Camera, survey and painting poles | 6061-T6, 6063-T5/T6 | Good balance of strength, cost and finish |
| Antenna and communication masts | 6061-T6, 6082-T6, 2024-T3/T4 | Stiffness and strength over long extensions |
| Medical and furniture stands | 6063-T5/T6, 6061-T6 | Excellent anodised appearance |
| Heavy industrial supports | 6082-T6, thick-wall 6061-T6 | Load capacity and weldability |
See telescopic tube, square telescopic tube and tent pole tube for size series.
Tapered aluminium tube and poles
A tapered tube is larger at one end than the other. The taper puts material where bending moments are highest, at the base of a pole, and reduces weight and wind area at the top. Lighting columns, flagpoles, sign posts, sailboat masts, antenna masts, sports equipment and robotic arms use it.
Tapers are produced by rotary swaging or spinning a straight tube over a tapered mandrel, by drawing, or for large poles by forming and welding tapered sheet. Short tapers and reduced ends are swaged; long, large-diameter poles are usually spun or fabricated. For 6xxx poles the tube is commonly formed in a softer temper and then solution treated and aged, so specify the final temper you need. The aluminium street light pole guide covers lighting columns in detail.
High-precision and special-purpose tube
Precision drawn tube
Cold-drawn round and square tube with close OD and wall tolerance, good concentricity and smooth bore, for pneumatic cylinders, optics, instruments and shafts. See precision drawn tube.
Heat-exchange tube
Round, flat-oval, inner-grooved and microchannel tube in 1xxx and 3xxx alloys for brazed heat exchangers. See heat exchanger tube.
Shell and housing tube
Thin- and thick-wall tube for motor housings, battery cans, torch bodies and sensor shells, often finished by CNC turning.
Pressure and gas tube
Seamless tube to ASTM B210 or B241 for hydraulic, pneumatic and gas service, tested by eddy current or hydrostatic pressure.
Large-diameter tube
Extruded or welded tube in large diameters for structures, rollers and vessels; see large-diameter tube and pipe.
Aerospace tube
Drawn 2024, 6061 and 7075 tube to AMS specifications, with full traceability and certification.
Alloys, tempers and achievable tolerances
| Alloy and temper | Typical tensile (MPa) | Strength in practice | Best suited to |
|---|---|---|---|
| 6063-T5 / T6 | 186 / 241 | Moderate | Complex thin-wall shapes, anodised appearance parts |
| 6061-T6 | 310 | Medium-high | Structural tube, bent frames (bent in O/T4), machined parts |
| 6082-T6 | about 310 – 340 | Medium-high | European structural tube, telescopic supports |
| 5052-H32 | 228 | Medium, non-heat-treatable | Bent tube, fuel lines, marine use |
| 2024-T3 | 483 | High | Aerospace struts and drawn tube |
| 7075-T6 | 572 | Very high | Poles, sports equipment, high-stress parts |
Typical values from Aluminum Association data; minimums depend on product form and standard and are reported on the mill certificate.
Tolerances come from the governing standard unless the drawing says otherwise. For extruded tube, ASTM B221 and EN 755-7 (seamless), EN 755-8 (porthole) and EN 755-9 (profiles) set the limits for diameter, wall, straightness and twist. Drawn tube to ASTM B210 or EN 754-7 holds closer diameter and wall tolerances. Any tolerance tighter than the standard must be shown on the drawing and agreed before order, because it may need drawing, sizing or machining. Over-specifying tolerances on surfaces that do not mate is one of the most common reasons custom tube costs more than it should.
Machining, finishing and quality checks
- Cutting and end work: precision cut-to-length, deburring, chamfering, flaring, beading, swaging and end forming
- Machining: drilling, slotting, threading, turning and milling of features to drawing
- Joining: TIG and MIG welding of tees, brackets and end caps where the design calls for it
- Surface finishes: anodising (clear, colour, hard), powder coating, electrophoretic coating, brushing and polishing
- Inspection: dimensional checks against the drawing, straightness and twist, surface inspection, and eddy-current or pressure testing where specified
- Documentation: EN 10204 3.1 mill test certificate, inspection report and first-article report on request
Order of operations matters: bending and forming usually come before final heat treatment and anodising, while precision machining often comes after heat treatment so that distortion is removed with the last cut.
How to order custom aluminium tube
- Send the drawingSection drawing (DWG, DXF, STEP or PDF), length, any bends or end features, quantity and expected annual volume.
- Material and standardAlloy and temper, governing standard (ASTM B221, B210, EN 755, AMS) and any testing.
- ReviewWe check manufacturability, suggest changes that lower cost or improve straightness, and confirm whether a new die or tooling is needed.
- Sample and approveWhere needed, first samples are produced and measured before the production run.
- DeliverTubes are protected, packed for export and shipped on EXW, FOB, CIF or DAP terms with mill certificates.
References and standards
- ASTM B221 – Aluminum and Aluminum-Alloy Extruded Bars, Rods, Wire, Profiles, and Tubes
- ASTM B210/B210M – Aluminum and Aluminum-Alloy Drawn Seamless Tubes
- EN 755-7, -8, -9 – Extruded rod/bar, tube and profiles: tolerances on dimensions and form
- EN 754-7 – Cold drawn rod/bar and tube: seamless tubes, tolerances
- The Aluminum Association – Aluminum Extrusion Manual and Aluminum Standards and Data
Custom aluminium (aluminum) tube: FAQ
Do I need a new extrusion die for a custom tube shape?
Usually yes, for any section that is not already available. Aluminium extrusion dies are relatively low cost compared with most metal-forming tooling, and the die can be reused for repeat orders. Sometimes an existing die is close enough after a small design change.
What is the tightest bend radius for aluminium tube?
With mandrel rotary-draw tooling and a formable alloy or soft temper, a centreline radius of about 1 to 1.5 times the outside diameter is achievable. 6061-T6 and 7075-T6 need larger radii or bending in a softer temper followed by heat treatment.
Is porthole-extruded tube strong enough for structural use?
Yes. Porthole tube has longitudinal weld seams formed under high pressure in the die and is used widely for structures, frames and vehicles. For high-pressure hydraulic or gas service, or where a code specifies it, order seamless tube instead.
Which alloy is best for telescopic poles?
7075-T6 gives the highest strength for thin, light poles; 6061-T6 is the economical all-rounder; 6063 is chosen for anodised appearance. The fit between tube stages matters as much as the alloy, so specify clearances after anodising.
How are tapered aluminium tubes made?
By rotary swaging or spinning a straight tube over a tapered mandrel, by drawing, or for large poles by forming and welding tapered sheet. Heat-treatable alloys are often formed soft and then heat-treated to T6.
What information do you need to quote a custom tube?
A drawing of the section and any bends or end features, alloy and temper, length, tolerances, surface finish, quantity, annual volume, governing standard and the destination for delivery.
Have a custom tube design?
Send your drawing and quantities. We will review manufacturability and quote the tube, processing and delivery.
