Hex outside, round bore
The most common type. The round bore can be drilled, reamed or tapped and suits threaded rod ends and bushings. Wall thickness varies between flats and corners, so specify the minimum wall the design needs.
Tube selection guide
Aluminium Hex Tube: Sizes, Alloys and Applications
Aluminium hex tube is an extruded hollow section with a hexagonal outside and either a round or hexagonal bore. It combines the spanner flats and anti-rotation of hex bar with much lower weight, and the bore can be threaded or used to pass cables and shafts. Most hex tube is 6061-T6/T6511 for strength or 6063-T5/T6 for appearance; this guide covers sizes, weights, section properties and how to specify it.
- Alloys
- 6061, 6063, 6082, 7075
- Bore
- Round or hexagonal
- Process
- Extruded, cut to length
- Standards
- ASTM B221 · EN 755
What aluminium hex tube is and why it is used
Hex tube is made by extruding a heated billet through a die with a mandrel or bridge that forms the bore. The result is a hollow bar with six flats outside, made in long lengths and cut to size. Because the shape comes from the die, almost any combination of across-flats size, wall thickness and bore shape can be produced.
Engineers choose it for three reasons. First, the flats: a hex tube part can be turned with a spanner, clamped flat in a fixture and prevented from rotating, which is why adjustable rod ends, tie rods and turnbuckles often use it. Second, the bore: a round bore can be tapped with left- and right-hand threads at opposite ends for length adjustment, and a hexagonal bore makes a sliding, torque-transmitting socket for a matching hex shaft. Third, weight: removing the core takes away material that contributes little to bending or torsional stiffness.
Hex tube is also used for its look. Hexagonal sections in anodised 6063 appear in furniture legs, lighting, shelving, display systems and architectural details, where they give a crisper appearance than round tube.
Round-bore and hex-bore hex tube
Hex outside, hex bore
Uniform wall all round. Used as a sliding sleeve or coupling over hex shafts and in telescoping assemblies where rotation must be locked.
Thin-wall hex tube
Walls of roughly 1–2 mm for frames, displays, lighting and furniture where loads are low and appearance and weight matter.
Thick-wall hex tube
Walls of about 4 mm and more for tie rods, linkages, tool bodies and machined fittings where threads or cross-holes need material around them.
Custom hex profiles
Hex sections with internal splines, screw ports, slots or multiple bores, made with a dedicated extrusion die.
Machined hex tube parts
Cut lengths, threaded ends, chamfers, cross-holes and slots added after extrusion to make finished components from tube stock.
Alloys and tempers for hex tube
| Alloy & temper | Typical tensile (MPa) | Typical yield (MPa) | Character | Typical uses |
|---|---|---|---|---|
| 6061-T6 / T6511 | 310 | 276 | Strong, weldable, very good machinability and corrosion resistance | Tie rods, linkages, drone and robot frames, fixtures |
| 6063-T5 | 186 | 145 | Excellent surface finish and anodising, easy to extrude thin walls | Furniture, lighting, displays, decorative trim |
| 6063-T6 | 241 | 214 | Better strength than T5 with the same finish | Architectural and light structural framing |
| 6082-T6 | 310 (EN min.) | 260 (EN min.) | European structural alloy, similar to 6061 | Structural parts to EN specifications |
| 7075-T6 / T6511 | 572 | 503 | Highest strength, not fusion-weldable, harder to extrude as hollow sections | Motorsport and aerospace links where weight is critical |
Typical values from the Aluminum Association and ASM; 6082 values are EN 755-2 specified minimums for extruded tube. Specified minimums for your size are stated on the mill certificate.
6061 and 6063 hollow sections are usually extruded through porthole dies, where the metal splits around the mandrel support and re-welds inside the die. This is normal and the welds are sound in these alloys. 7075 is harder to extrude as a porthole hollow, so 7075 hex tube is less common and is sometimes made from seamless round tube or machined from bar instead.
Hex tube sizes, weights and section properties
Hex tube is described by across-flats size (AF) and wall thickness, or by AF and bore diameter for round-bore tube. The table gives calculated values for hex-bore (uniform wall) tube in 6061 at 2.70 g/cm³. The second moment of area is the same about any axis through the centre of a regular hexagon, which is one practical advantage of the shape: stiffness does not depend on orientation.
| AF (mm) | Wall (mm) | Area (mm²) | Weight (kg/m) | Second moment I (cm⁴) |
|---|---|---|---|---|
| 12 | 1.5 | 55 | 0.147 | 0.09 |
| 16 | 2 | 97 | 0.262 | 0.27 |
| 19 | 2 | 118 | 0.318 | 0.48 |
| 22 | 2 | 139 | 0.374 | 0.78 |
| 25 | 2 | 159 | 0.430 | 1.18 |
| 25 | 3 | 229 | 0.617 | 1.57 |
| 30 | 2 | 194 | 0.524 | 2.12 |
| 30 | 3 | 281 | 0.758 | 2.88 |
| 32 | 3 | 301 | 0.814 | 3.56 |
| 38 | 3 | 364 | 0.982 | 6.23 |
| 40 | 4 | 499 | 1.347 | 9.09 |
| 50 | 3 | 488 | 1.319 | 15.05 |
| 50 | 5 | 779 | 2.104 | 22.19 |
| 60 | 5 | 953 | 2.572 | 40.35 |
| 75 | 6 | 1434 | 3.872 | 95.55 |
| 100 | 8 | 2550 | 6.884 | 301.98 |
Calculated from nominal geometry with sharp corners: area = 0.866 × (AF² − AFi²), I = 0.0601 × (AF⁴ − AFi⁴), where AFi = AF − 2 × wall. For round-bore tube, area = 0.866 × AF² − πd²/4.
Common imperial sizes run from about 3/8 in to 2 in across flats with 1/16 in to 1/4 in walls, and round-bore tubes are often sized so the bore takes a standard tap: for example a 7/8 in hex with a 0.562 in bore suits a 5/8 in thread, and a 1-1/8 in hex with a 0.687 in bore suits a 3/4 in thread. Check tap-drill size and minimum wall at the flats before fixing the bore.
Hex tube compared with round tube, square tube and hex bar
Is a hexagonal tube stiffer than a round or square tube? It depends on what is held equal. At the same outside width, a hex tube is stiffer than a round tube because it contains more material, and less stiff than a square tube of the same width for the same reason. At equal weight, the three shapes are close in bending, and round tube remains the most efficient in torsion. Choose hex for its flats and anti-rotation, not because it is inherently stronger.
| Shape (width W, solid) | Area | Second moment I | Main advantage |
|---|---|---|---|
| Round, diameter W | 0.785 W² | 0.049 W⁴ | Best torsional efficiency, easy to bend and turn |
| Hexagon, W across flats | 0.866 W² | 0.060 W⁴ | Spanner flats, anti-rotation, orientation-independent stiffness |
| Square, side W | 1.000 W² | 0.083 W⁴ | Highest bending stiffness at a given width, flat mounting faces |
Compared with solid hex bar, hex tube saves weight and leaves a bore for threads or cables, at the cost of lower load capacity in compression and lower thread engagement. If a part sees high axial load or needs deep threads in solid material, hex bar may be the better stock; see our aluminium hex bar guide.
Machining, welding and finishing hex tube
Cutting
Saw with carbide blades for square, burr-free ends. For decorative parts, specify cut length tolerance and end finish.
Threading
Tap round bores with sharp, polished taps and cutting fluid. In 6061-T6 thread engagement of about 1.5–2 × diameter is common for load-bearing joints; use thread inserts where parts are frequently adjusted.
Welding
6061 and 6063 weld readily by TIG or MIG with ER4043 or ER5356 filler. The heat-affected zone loses strength, so keep welds away from highly stressed threaded ends.
Anodising
6063 gives the most uniform decorative finish; 6061 anodises well in clear and black. Anodising adds a few microns to dimensions and coats threads, so mask or chase threads if needed.
Powder coating
Durable coloured finish for furniture, railings and displays; not used on precision fits or threads.
Bending
Hex tube can be bent with shaped tooling, but the flats tend to distort. Bend in O or T4 temper and age afterwards where tight bends are needed.
Where aluminium hex tube is used
- Motorsport and vehicles: adjustable tie rods, toe links and turnbuckles with left- and right-hand threaded ends, usually 6061-T6 anodised black
- Drones and UAV frames: lightweight arms and standoffs in 6061-T6 or 7075-T6
- Automation and fixtures: spacers, guide sleeves, clamp bodies and sliding couplings over hex shafts
- Robotics: link members, cable-carrying standoffs and anti-rotation sleeves
- Furniture and lighting: table and chair legs, lamp stems, shelving posts, mostly 6063-T5 anodised
- Architecture and display: balustrade elements, decorative grilles and exhibition frames
- Tools and hardware: tool handles, extension bars and connectors where flats help grip
How to specify aluminium hex tube
- SectionAcross-flats size, wall thickness (hex bore) or bore diameter (round bore), or a section drawing for custom shapes.
- Alloy and temper6061-T6/T6511 for structural and threaded parts, 6063-T5/T6 for decorative parts, 7075 only where strength justifies it.
- Standard and tolerancesASTM B221 with ANSI H35.2 tolerances, or EN 755-2 with EN 755-8/-9 tolerances. Note any tighter requirement.
- Length and processingMill lengths or cut lengths, plus threading, chamfering, cross-holes or slots if needed.
- Finish and documentsMill finish, anodised colour or powder coat; EN 10204 3.1 certificate; packing and Incoterms (EXW, FOB, CIF or DAP).
References and standards
- ASTM B221 – extruded bars, rods, wire, profiles and tubes
- ANSI H35.2 – Dimensional Tolerances for Aluminum Mill Products
- EN 755-2 – extruded rod, bar, tube and profiles: mechanical properties
- EN 755-9 – extruded profiles: tolerances on dimensions and form
- The Aluminum Association – alloy designations and typical properties
Aluminium (aluminum) hex tube: frequently asked questions
What alloy is aluminum hex tube made from?
Mostly 6061-T6 or T6511 for structural and threaded parts and 6063-T5 or T6 for decorative uses. 6082-T6 is common for EN-specified work, and 7075 is used occasionally where maximum strength is needed.
Can the bore of a hex tube be threaded at both ends?
Yes. Round-bore tube is often tapped with a right-hand thread at one end and a left-hand thread at the other, so a rod can be adjusted in length by turning the tube. Check that the wall at the flats is thick enough for the thread.
How do I calculate the weight of hex tube?
For uniform-wall tube, area = 0.866 × (AF² − (AF − 2t)²). Multiply area in mm² by 0.0027 to get kg/m for 6061. A 25 mm AF tube with a 2 mm wall weighs about 0.43 kg/m.
Is hex tube stronger than round tube?
At the same outside width a hex tube is stiffer because it contains more metal. At equal weight, hex and round tubes are similar in bending and round tube is better in torsion. Hex is chosen mainly for its flats.
What is the difference between hex tube and hex bar?
Hex bar is solid and suits high-load parts and deep threads. Hex tube is hollow, lighter, and leaves a bore for threads, shafts or cables.
Can you supply custom hex tube sections?
Yes. Custom across-flats sizes, walls and bore shapes are extruded from a dedicated die to your drawing, and tube can be cut, threaded or machined to order.
Looking for aluminium hex tube?
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