Anodising
Clear or coloured sulphuric anodising for corrosion resistance and identification; hard anodising for wear. Allow for coating build-up on thread fits.
Buyer guide · Threaded rod and studs
Aluminium Threaded Rod and Studs: Alloys, Sizes and Load Capacity
Aluminium threaded rod (all-thread) is a headless rod threaded along its full length, or at the ends only, used where a fastener must be light, non-magnetic, corrosion-resistant or galvanically compatible with aluminium structures. It is normally made from 6061-T6, 2024-T4 or 7075 bar to ASTM B211, threaded to ISO metric or Unified inch standards. This guide gives thread sizes, calculated tensile loads by alloy, and the practical rules for using aluminium threads without galling or corrosion.
- Alloys
- 6061-T6 · 2024-T4 · 7075-T6/T73
- Threads
- M3 – M30 · #10 – 1 in UNC/UNF
- Material standard
- ASTM B211 · ASTM F468
- Density
- About one third of steel
What is aluminium threaded rod?
Threaded rod comes in three basic forms: all-thread rod, threaded end to end and cut to length with nuts used at any point; double-end studs, threaded at both ends with a plain centre; and single-end or tap-end studs, threaded at one end for screwing into a tapped hole. Aluminium versions do the same jobs as steel rod but at about one third of the weight.
Aluminium rod is chosen not for raw strength, where steel and stainless steel are far ahead, but for what it adds to an assembly: low mass in aircraft, vehicles, drones and portable equipment; no magnetism for instruments, MRI rooms and electronics; good electrical and thermal conductivity for busbar clamps and grounding; and, most often, compatibility with aluminium structures, because an aluminium stud in an aluminium frame avoids the galvanic corrosion that steel or copper fasteners can cause in wet conditions.
The rod is made from extruded or cold-finished bar. Threads are either cut (by die-head, lathe or CNC) or rolled. Rolling displaces rather than removes metal, so the grain flows around the thread form, the root is smooth and work-hardened, and fatigue strength is noticeably better. Rolled threads are preferred for production quantities and fatigue-loaded joints; cut threads suit short runs, large diameters and special forms.
Alloys for aluminium threaded rod
Specified minimum properties below are for rolled or cold-finished rod to ASTM B211; typical values are higher. Fastener-grade aluminium is also covered by ASTM F468, which lists 2024-T4, 6061-T6 and 7075-T73 for bolts, screws and studs.
| Alloy & temper | Min. tensile strength | Min. yield strength | Characteristics | Typical use |
|---|---|---|---|---|
| 6061-T6 | 290 MPa (42 ksi) | 240 MPa (35 ksi) | Good strength, excellent corrosion resistance, anodises well, weldable | General purpose, marine, structural and electrical fixings |
| 2024-T4 | 425 MPa (62 ksi) | 275 MPa (40 ksi) | High strength and fatigue resistance; needs corrosion protection (anodise or chromate-free conversion coat) | Aerospace studs and high-load fixings |
| 7075-T6 | 530 MPa (77 ksi) | 455 MPa (66 ksi) | Highest strength; susceptible to stress corrosion in T6 | High-load studs in dry or protected environments |
| 7075-T73 | Lower than T6 | Lower than T6 | Over-aged for much better stress-corrosion resistance | Aerospace fasteners exposed to moisture |
| 6063-T6 | About 205 MPa (30 ksi) | About 170 MPa (25 ksi) | Lower strength, very good corrosion resistance and finish | Light-duty decorative and display fixings |
| 5052 / 5056 | Lower (strain-hardened) | — | Very good corrosion resistance, especially in seawater | Light marine fixings; 5056 is common for rivets |
Values are specified minimums for bar and rod and vary by diameter and temper designation (for example T651, T6511, T351). The mill certificate for the rod lot is the controlling document.
Metric aluminium threaded rod: sizes and tensile loads
ISO metric coarse threads to ISO 261/262 with tolerance class 6g are standard; fine pitches (for example M10 × 1.25, M12 × 1.5) are available for adjustment and vibration resistance. Threaded rod dimensions follow DIN 976-1, which has replaced DIN 975. Loads below are calculated as tensile stress area × specified minimum tensile strength; they are breaking loads, not working loads, so apply a suitable safety factor.
| Thread | Pitch (mm) | Stress area (mm²) | Min. breaking load 6061-T6 (kN) | 2024-T4 (kN) | 7075-T6 (kN) |
|---|---|---|---|---|---|
| M3 | 0.5 | 5.0 | 1.5 | 2.1 | 2.7 |
| M4 | 0.7 | 8.8 | 2.5 | 3.7 | 4.7 |
| M5 | 0.8 | 14.2 | 4.1 | 6.0 | 7.5 |
| M6 | 1 | 20.1 | 5.8 | 8.6 | 10.7 |
| M8 | 1.25 | 36.6 | 10.6 | 15.6 | 19.4 |
| M10 | 1.5 | 58.0 | 16.8 | 24.6 | 30.7 |
| M12 | 1.75 | 84.3 | 24.4 | 35.8 | 44.7 |
| M14 | 2 | 115.4 | 33.5 | 49.1 | 61.2 |
| M16 | 2 | 156.7 | 45.4 | 66.6 | 83.0 |
| M20 | 2.5 | 244.8 | 71.0 | 104.0 | 129.7 |
| M24 | 3 | 352.5 | 102.2 | 149.8 | 186.8 |
| M30 | 3.5 | 560.6 | 162.6 | 238.2 | 297.1 |
For comparison, an M10 rod in property class 4.8 steel (400 MPa minimum tensile) breaks at about 23 kN, so 6061-T6 rod carries roughly 70 % of the load of low-strength steel rod at about 35 % of the weight, while 7075-T6 rod exceeds it.
Inch (UNC / UNF) aluminium threaded rod
Unified inch threads to ASME B1.1 are standard in North America, usually class 2A for external threads (2B for nuts). Class 3A is specified for precision fits. Stress areas use the ASME B1.1 formula; loads are calculated with the same minimum strengths as above.
| Size | UNC TPI | UNF TPI | UNC stress area (in²) | Min. breaking load 6061-T6, UNC (lbf) | 7075-T6, UNC (lbf) |
|---|---|---|---|---|---|
| #10 | 24 | 32 | 0.0175 | 736 | 1,350 |
| 1/4 | 20 | 28 | 0.0318 | 1,336 | 2,450 |
| 5/16 | 18 | 24 | 0.0524 | 2,202 | 4,037 |
| 3/8 | 16 | 24 | 0.0775 | 3,255 | 5,967 |
| 7/16 | 14 | 20 | 0.1063 | 4,465 | 8,186 |
| 1/2 | 13 | 20 | 0.1419 | 5,960 | 10,926 |
| 5/8 | 11 | 18 | 0.2260 | 9,492 | 17,402 |
| 3/4 | 10 | 16 | 0.3345 | 14,047 | 25,753 |
| 7/8 | 9 | 14 | 0.4617 | 19,393 | 35,554 |
| 1 | 8 | 12 | 0.6057 | 25,441 | 46,642 |
Rounded-root forms (UNR and the aerospace UNJ series, with a controlled root radius) improve fatigue life and are specified for studs on aircraft and high-cycle equipment.
Design rules for aluminium threaded joints
- Galling: aluminium threads, especially aluminium on aluminium, can gall and seize under high torque. Use a thread lubricant or anti-seize free of copper and graphite (both promote galvanic corrosion of aluminium), or anodise one part.
- Thread engagement: when a stud screws into a tapped aluminium part, use a longer engagement than in steel, commonly 1.5 – 2 × diameter, or fit helical thread inserts for repeated assembly.
- Preload and torque: base tightening torque on the rod alloy and lubricant; aluminium needs lower torque than steel of the same size. Use washers to spread bearing load on soft parts.
- Galvanic corrosion: keep aluminium rod away from bare copper, brass and carbon steel in wet service. Stainless steel nuts on aluminium rod need isolating washers and sealant in marine conditions.
- Creep and temperature: 6xxx and 7xxx alloys lose strength with long exposure above about 100 – 150 °C, and preload relaxes. Choose steel or titanium for hot joints.
- Thermal expansion: aluminium expands about twice as much as steel; an aluminium stud clamping aluminium parts keeps preload steadier through temperature cycles than a steel one.
Finishes, inspection and documentation
Conversion coating
Chromate-free conversion coatings protect 2024 and 7075 and act as a paint base.
Thread inspection
GO/NO-GO ring and plug gauges for the specified class (6g/6H or 2A/2B); pitch and major diameter checks.
Mechanical testing
Tensile and hardness tests on the rod lot; proof-load testing of studs where required.
Material certification
Mill test certificate to EN 10204 3.1 with chemistry and properties of the bar.
Traceability
Lot marking and packing labels linking each bundle to its certificate.
Where aluminium threaded rod is used
| Industry | Typical alloy | Examples |
|---|---|---|
| Aerospace | 2024-T4, 7075-T73 | Studs, tie rods and fixings to AMS or customer specifications |
| Automotive and motorsport | 7075-T6, 6061-T6 | Lightweight studs, suspension adjusters and brackets |
| Marine | 6061-T6, 5052 | Fixings into aluminium hulls, superstructures and deck fittings |
| Electrical | 6061-T6 | Busbar clamps, grounding studs and terminal fixings |
| Building and solar | 6061-T6 | Fixings for aluminium cladding sub-frames and solar mounting rails |
| Automation and laboratory | 6061-T6, 7075-T6 | Non-magnetic frames, spacers and adjusters |
Common mistakes with aluminium threaded rod
Treating it like steel rod
Swapping a steel rod for the same size in aluminium without checking load can halve the capacity. Size up or choose 7075 where strength matters.
7075-T6 in wet service
T6 is prone to stress-corrosion cracking under sustained tension in moist environments. Specify 7075-T73 or 6061-T6 instead.
Copper-based anti-seize
Common copper or graphite anti-seize compounds accelerate corrosion of aluminium. Use a nickel, zinc or aluminium-compatible product.
Ignoring coating build-up
Anodising adds thickness to both flanks of the thread; specify whether the thread class applies before or after coating.
Over-torquing
Aluminium threads strip or gall at torques that are normal for steel. Use calibrated tools and published torque values for the alloy.
Unclear stud lengths
For double-end and tap-end studs, give overall length and each thread length on the drawing, not just "M12 × 100".
How to order aluminium threaded rod
- SpecifyThread size, pitch and class, rod type (all-thread, double-end or tap-end stud), length and thread lengths, alloy and temper.
- FinishMill, anodised or conversion coated; any special packaging for threads.
- QuoteWe confirm material, threading method (cut or rolled), certification and delivery terms (EXW, FOB, CIF or DAP).
- InspectThread gauging, dimensional check and EN 10204 3.1 certificate for the bar.
- ShipPacked with thread protection in cartons or crates for sea or air freight worldwide.
References and standards
- ASTM B211 – Aluminum and Aluminum-Alloy Rolled or Cold-Finished Bar, Rod, and Wire
- ASTM F468 – Nonferrous Bolts, Hex Cap Screws, Socket Head Cap Screws, and Studs for General Use
- ASME B1.1 – Unified Inch Screw Threads (UN, UNR and UNJ Thread Form)
- ISO 261 / ISO 965-1 – ISO general-purpose metric screw threads: general plan and tolerances
- DIN 976-1 – Stud bolts: metric thread
Aluminium (aluminum) threaded rod: frequently asked questions
How strong is aluminum threaded rod?
It depends on the alloy. Using specified minimum tensile strengths, an M10 rod breaks at about 17 kN in 6061-T6, 25 kN in 2024-T4 and 31 kN in 7075-T6. Apply a safety factor for working loads.
Which aluminium alloy is best for threaded rod?
6061-T6 for general and marine use thanks to its corrosion resistance; 2024-T4 or 7075-T73 for high-strength aerospace studs; 7075-T6 for maximum strength in dry, protected conditions.
How do I stop aluminium threads from galling?
Use a copper-free and graphite-free anti-seize or thread lubricant, avoid over-torquing, consider anodising one of the mating parts, and use helical inserts in tapped aluminium holes that are assembled repeatedly.
Can I use stainless steel nuts on aluminium rod?
Yes in dry conditions. In wet or marine service, isolate the metals with nylon or neoprene washers and sealant, or use aluminium nuts, to limit galvanic corrosion.
Are rolled threads better than cut threads?
For fatigue-loaded joints, yes: rolling work-hardens the root and keeps the grain continuous, which improves fatigue life. Cut threads are fine for static loads and short runs.
Do you supply studs to drawing?
Yes. Metline supplies aluminium threaded rod and studs to drawing, in metric and inch threads, with mill certificates for the bar.
Need aluminium threaded rod or studs?
Send thread, alloy, length and quantity. Our team will reply with availability, certification and a delivered price anywhere in the world.
