A round aluminium extrusion is any profile whose cross-section is built around a circle: solid rod, hollow tube, half and quarter rounds, and functional rounds with fins, ribs, slots or internal grooves. Most are pushed from 6063, 6061 or 6082 billet, and the right choice depends on whether the part is decorative, structural, thermal or a precision bore. This guide explains each family, which alloy and temper to order, and what to put on the drawing.
Extrusion forces a heated aluminium billet (typically 450 – 500 °C) through a steel die, producing a continuous length with a constant cross-section. A round die opening is the simplest shape to extrude, which is why round bar and round tube are the cheapest and most widely stocked aluminium sections in the world.
From that simple start, designers add features that a drawn or rolled tube cannot carry: radial fins for cooling, a T-slot for bolting accessories, a glazing groove in a handrail, internal teeth for heat transfer, or several internal channels for fluid or cable routing. Because the die cost is modest compared with machining or casting the same features, an extruded round often replaces an assembly of several parts.
For buying purposes it helps to group round extrusions into four families: solid (rod, half round), hollow (tube, half and quarter round tube), structural (thick-wall tube, cylinder barrels, multi-void rounds) and functional (finned, ribbed, grooved, slotted, perforated). Each family has different tolerance, alloy and finishing priorities.
Extruded rod from a few millimetres to several hundred millimetres in diameter. Used for shafts, pins, bushings and machined parts. Large diameters are extruded on heavy presses; small precise diameters are often cold-drawn after extrusion.
A solid D-shaped section (180° arc with a flat face). Light and economical for edge trims, furniture nosings, stair edge guards and handles where only one face is visible.
Seamless (porthole or mandrel) or structural hollow round. The most versatile section: railings, handrails, frames, tent poles, machinery columns and transport structures.
Hollow 180° or 90° arcs, often with a flange or flat for fixing. Used as corner protectors, cable covers, drainage channels, cabinet transitions and trim.
A round outer surface with two or more internal cavities separated by webs. Gives high torsional and bending stiffness and allows separate channels for fluids or wiring.
A round column with one or more T-slots, used in automation frames, display systems and lighting. Accepts standard slot nuts and connectors.
Outer surface with longitudinal ribs for grip, decoration or to stiffen thin walls. Commonly supplied in imperial sizes such as 1/2, 5/8, 3/4, 7/8 and 1 in OD.
Radial fins extruded integrally with the core, so there is no contact resistance between fin and tube. Straight or angled fins are extruded; pin fins are produced by cross-cutting.
Internal teeth for HVAC heat transfer, or a precision bore that is honed or skived for pneumatic and hydraulic cylinders.
6xxx alloys dominate because they extrude quickly, quench at the press and anodise well. Typical minimum properties below are for extruded products to ASTM B221 / EN 755-2; actual values for your lot appear on the mill certificate. Values for thick walls and large diameters may be lower, so check the thickness band in the standard.
| Alloy-temper | Min. tensile (MPa) | Min. yield (MPa) | Best suited to |
|---|---|---|---|
| 6063-T5 | 150 | 110 | Architectural rounds, handrails, trims, heat sinks (≤ 12.5 mm wall) |
| 6063-T6 | 205 | 170 | Railings, furniture tube, finned tube needing a little more strength |
| 6060-T66 (EN) | 195 – 215 | 150 – 160 | European architectural and thermal profiles |
| 6005A-T6 | 250 – 270 | 200 – 225 | Structural hollows with thin walls, transport frames |
| 6061-T6 / T6511 | 260 | 240 | Shafts, columns, cylinder barrels, machined parts |
| 6082-T6 | 290 – 310 | 250 – 260 | Heavy structural tube and bar (common in Europe, India) |
| 7075-T6 / T6511 | 540 – 560 (by diameter) | 480 – 500 (by diameter) | Small high-stress rods and tubes; not for welded parts |
7075 values vary with diameter; 6005A and 6082 values vary with wall thickness. Always design to the minimums in the governing standard.
Temper notes. T5 means cooled at the press and artificially aged; it is the economical temper for 6063. T6 adds a full solution treatment (or a severe press quench) for higher strength. T6511 and T6510 are stretched to relieve residual stress, so bar and tube stay straight when machined, which matters for shafts and bores. For tight bending, order O or T4 and age after forming.
| Standard | Covers | Notes |
|---|---|---|
| ASTM B221 / B221M | Extruded bar, rod, wire, profiles and tube | General engineering; not for pressure-carrying tube |
| ASTM B241 / B241M | Seamless pipe and seamless extruded tube | Use for pressure or fluid service |
| ASTM B429 | Extruded structural pipe and tube | Structural round and pipe sizes |
| ANSI H35.2 | Dimensional tolerances for wrought products | Referenced by ASTM product standards |
| EN 755-1/-2/-8/-9 | Extruded rod, bar, tube and profiles | Properties (part 2), tolerances (parts 8 and 9) |
| EN 12020-2 | Precision profiles in 6060 / 6063 | Tighter tolerances for architectural sections |
| SAE AMS-QQ-A-200 series | Aerospace extrusions | For aerospace and defence orders |
If a round extrusion carries fluid under pressure, specify B241 seamless tube rather than B221 structural tube; porthole-die tube contains longitudinal weld seams that are fine for structures but are not qualified for pressure service. For pipe sizes and schedules see our aluminium pipe size chart.
Round extrusions are toleranced on diameter (mean and at any point), wall thickness, concentricity or eccentricity for tubes, straightness, twist (for slotted or finned rounds) and cut length. Standard tolerances come from ANSI H35.2 or EN 755-8/-9 and get wider as the diameter grows and as the alloy gets harder to extrude.
For precision applications such as cylinder bores or bearing seats, it is usually cheaper to order standard extrusion tolerances and specify honing, skiving or cold drawing for the critical surface than to push the extrusion die beyond its natural capability.
A round top-rail with a single or double slot that grips glass, acrylic, polycarbonate or composite infill panels with a gasket. Usually 6063-T5 or 6061-T6, anodised or powder coated. Metline supplies the extruded profile; the fabricator cuts, bends and installs the railing.
Tube with round, slotted or square holes punched or laser-cut after extrusion. Used for silencers, filters, drainage and ventilation. Open area and hole pattern decide flow and remaining strength.
Radial fins around a solid or hollow core give 360° heat spreading for LED lamps, motor drives and power electronics. 6063 is preferred for its thermal conductivity (around 200 W/m·K in T5).
Finned round shells for EV, industrial and servo motors, inverters and compressors. The extrusion is cut to length and machined at the bore and ends; integral cooling channels can be extruded into the wall.
Fins extruded in one piece with the tube wall for heat exchangers, condensers and HVAC coils. No bonding interface, so heat transfer is efficient and fins cannot detach.
Round or square-outside tube with a honed or skived bore for pneumatic and hydraulic actuators. Typically 6061-T6 or 6063-T6, hard anodised in the bore for wear.
Round sections are bent on rotary-draw or roll benders. A practical guide for 6063-T5 tube is a centreline radius of at least 2 – 3 times the outside diameter with a mandrel; 6061-T6 needs more, or bending in T4 followed by ageing. Thin walls wrinkle on the inside of the bend, so give the bender the wall thickness and radius before ordering.
6061 and 6082 machine cleanly in T6; 6063 is softer and can be gummy, so sharp tools with high rake angles help. MIG and TIG welding with 4043 or 5356 filler is routine, but the heat-affected zone of a T6 extrusion drops close to T4 strength. Design welded handrails and frames accordingly, or place welds in low-stress areas.
| Finish | What it gives | Watch-outs |
|---|---|---|
| Mill finish | Lowest cost; natural oxide protection | Handling marks; die lines visible |
| Anodising (AA10 – AA25) | Hard, durable, colour-stable surface | Use anodising-quality 6063 for consistent colour |
| Hard anodising | Wear-resistant bore or shaft surface | Adds dimensional growth; allow for it |
| Powder coating | Any RAL colour, good outdoor durability | Coating thickness affects tight fits |
| Brushing / polishing | Decorative satin or bright finish | Usually followed by clear anodising |
Extruded tube is pushed hot through a die and has as-extruded tolerances and surface. Drawn tube is extruded first and then pulled cold through a smaller die over a mandrel, giving tighter diameter and wall tolerances, a smoother surface and higher strength in strain-hardened tempers.
6063-T5 or T6 is the usual choice: it bends well, anodises evenly and is strong enough for most railing designs. 6061-T6 is used where higher strength is needed and appearance is less critical.
Yes. Radial fins, T-slots, glazing grooves, ribs and internal channels can all be built into the die. A new die is needed for a custom section, which is why custom profiles are economical when the quantity justifies the tooling.
Only seamless tube made to ASTM B241 (or an equivalent pressure specification) should be used for pressure service. Porthole-die structural tube to ASTM B221 has internal weld seams and is meant for structures.
Mill lengths of about 5.8 – 6 m are common for shipping in containers, and the extrusion can be cut to any length you specify, with a length tolerance agreed on the order.
Yes. Metline ships round bar, tube and custom round profiles worldwide from Mumbai, with mill certificates and export packing.
Send the section, alloy, temper, finish and quantity. Our team will confirm tooling, tolerances and a delivered price.
