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6061 or 6082: which aluminium should the drawing call for?
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#6061 vs 6082#6082-T6#6061-T6#aluminium grade for CNC machining#material callout on drawing#decorative anodising

6061 or 6082: which aluminium should the drawing call for?

Uzair bin Haroon

For most machined parts it does not matter, so do not make the shop choose for you: write both. 6061 and 6082 are both heat-treatable aluminium-magnesium-silicon alloys, and in the T6 temper 6082 meets or beats 6061's minimum strength. A note that reads "6061-T6 or 6082-T6" lets the shop cut whichever bar or plate it can buy fastest. Name one grade only when the part gets a decorative anodise, when a customer, standard or certificate names it, or when your strength calculation used 6082's figures.

This follows the earlier guide on using aluminium instead of stainless for a machined part, which quotes 6082-T6. If your drawing says 6061, the answer below tells you whether to change it.

Why are they interchangeable on most parts?

Because they differ in a few minor alloying elements, not in kind. Both get their strength from magnesium and silicon and the same solution-treat-and-age process. 6082 adds manganese for toughness. 6061 carries a little copper and chromium instead. On the minimum properties a designer works to, the two sit close together:

6061-T66082-T6
Manganese0-0.15%0.40-1.00%
Copper0.15-0.40%0-0.10%
Minimum proof stress, extruded bar and profile (EN 755-2)240 MPa250-260 MPa
Minimum tensile strength, same260 MPa290-310 MPa

A part designed around 6061-T6's minimums is therefore safe in 6082-T6. UK stockist Aalco notes that 6082's higher strength "has seen it replace 6061 in many applications", which is why one shop's rack holds 6082 and the next one's holds 6061. Machining is not a reason to choose: Aalco says 6082 in T6 "machines well", and Hydro gives it the top mark for machinability among its extrusion alloys.

The temper matters far more than the grade. Hydro's datasheet gives 6082 in T4 a minimum proof stress of 110 MPa, less than half the 250 MPa of T6. A note that says "6082" with no temper lets the shop supply something much weaker.

When should the drawing name only one?

In four cases. Outside them, the second grade costs you nothing.

  • A decorative anodise. Hydro states that manganese makes 6082 "less suitable for decorative anodising", and rates it 2 out of 5 against 5 for 6060 and 6063. If the part is anodised for looks, or several parts must match in colour, name 6061 and ask for a colour sample. A hard anodise for wear does not need this.
  • A customer or industry specification names the grade. Copy it exactly, including the standard. Substituting it is the customer's decision, not the shop's.
  • You need traceable material. The 3.1 certificate will name one alloy and one heat. That is fine with an either-or note, but if your quality plan lists one grade, the drawing has to match it.
  • Your calculation used 6082's numbers. 6061's minimum tensile strength is up to 50 MPa lower. If the part was sized to 6082's 290-310 MPa with little margin, either check it against 6061's figures or name 6082 alone.

How should the note be written?

Name both grades and the temper, then the product form and any certificate. For a part machined from plate or thick bar, T651 is the version to ask for: it is stretched to relieve internal stress after heat treatment, so it moves less when you cut deep pockets. A complete note reads:

MATERIAL: ALUMINIUM 6061-T6/T651 OR EN AW-6082-T6/T651. MATERIAL CERTIFICATE EN 10204 3.1 TO BE SUPPLIED.

Avoid "6061 or equivalent". It leaves the shop to decide what counts as equivalent, and a quote can come back on an alloy you did not mean. Name the alternative yourself. Note too that the 6061 figures in the table are for extrusions up to 200 mm across and the 6082 plate figures in Aalco's datasheet fall to 240 MPa above 12.5 mm thick, so check the minimums for the stock size your part is cut from.

What does the second grade gain you?

Mainly time and more quotes. A shop that already has one grade in the right size can start straight away, and does not have to buy a full bar of the other for your part. More shops can quote the same drawing, so the prices you compare are real. The quote study behind the stainless-versus-aluminium post showed how much the material note decides who bids.

Send your drawing to Vesprr Workshop with "6061-T6 or 6082-T6" on the note, and ask for the quote to state which grade and certificate will be supplied.

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