CNC machined Aluminum Alloys in 6061, 6082 and 7075
Aluminum is the only material on this site where the lightweight is not the interesting part. The interesting part is that the three grades most drawings call out — 6061, 6082 and 7075 — have almost identical stiffness, and differ mainly in what they cost you in welding, anodizing and distortion. XS Precision machines all three into Automation components, Structural parts and Electronic housings, and tells you when the grade on the drawing is the wrong one.
Every part below was quoted against the alloy, the temper and the finish together, because those three decide the price together.
Stiffness is the same in all three. Everything else is not.
Elastic modulus for 6061, 6082 and 7075 sits between 69 and 71.7 GPa — inside the scatter of the test method. If your part is deflection-limited rather than strength-limited, paying three times the bar price for 7075 buys you nothing but a lighter wallet. These six numbers are the ones that actually move a design.
6061, 6082 and 7075 are not three grades of the same aluminum
Aluminum Alloys sort into families before they sort into grades. Two of these three sit in the same family and differ by one element. The third is a different metallurgy entirely — a zinc-bearing alloy that behaves more like a mild steel in the machine and much worse in a weld. Reading the table below in the wrong order is how specifications go wrong before anyone cuts metal.
Stock form decides what you can actually buy. 6061 is stocked almost everywhere in plate, round bar, hex, tube and a long catalogue of extrusion profiles, which is why it wins on lead time without anyone deciding it should. 6082 is thinner on the ground outside Europe — plate and extruded bar are easy to find, thin sheet and small-diameter round are not. 7075 plate is routinely available in T6 and T651, while T7351 and T73 round bar are a mill-order item in most markets. Establish which forms the grade actually comes in before the drawing calls for it.
6082 is the manganese alloy. 6061 is the copper alloy.
Every downstream difference between the two — strength, anodizing color, corrosion behavior, price — traces back to those two lines of the chemistry table. ASTM B221 allows 6061 up to 0.40% copper and no more than 0.15% manganese. EN 573-3 allows 6082 up to 1.00% manganese and no more than 0.10% copper. That is the whole story.
Neither of them is a marine alloy. Both 6061 and 6082 are routinely described as corrosion resistant, and in atmospheric and fresh-water service they are. But for continuous seawater immersion or salt spray, the grade that belongs on the drawing is 5083 or 5251 from the 5xxx family, which cannot be heat treated and so cannot lose that strength in a weld. When a customer asks us for “6061 for a boat part”, we say so before quoting.
7075 gives you 570 MPa. Which temper gives it is the real question.
Alloy and temper are not the same material specification. 7075-T6 and 7075-T73 share a chemistry number and almost nothing else that matters. Moving from T6 to T73 costs roughly 12–15% of tensile strength and buys about an order of magnitude of stress-corrosion resistance, plus fracture toughness that rises from around 20–24 to 28–33 MPa·√m. On a part that sees sustained load in humid or coastal air, that is not a compromise — it is the only correct answer.
Aluminum machines 5 to 10 times faster than steel. That is exactly why the mistakes are expensive.
Good machinability is the property buyers quote first and define least. Because it cuts so easily, aluminum forgives a bad program right up to the point where it does not. Two failures account for nearly every scrap part in our aluminum cell: heat welded into a thin wall that moves after unclamping, and a built-up edge from a dull or wrongly coated tool that drags the surface instead of shearing it.
Three rules decide whether aluminum comes off the machine looking like a part or like a mistake:
All speeds in m/min, feed in mm per revolution or mm per tooth, on uncoated polished carbide with high-pressure coolant. Treat these as shop-floor starting points and tune them to your spindle, your tool length and your fixturing — a long, thin cutter in a soft setup cannot take the same parameters as a short one in a solid vice.
Lightweight is not an advantage if the part has to be scrapped at final inspection
Anodizing a whole heat sink is fine. Anodizing the contact face is an engineering error.
Aluminum oxide conducts heat at 15–30 W/m·K, roughly one tenth of the aluminum beneath it, which sounds disqualifying and is not. The layer is only microns thick. A 25 µm Type II coating on 6061-T6 adds about 1.25 × 10⁻⁶ m²·K/W of thermal resistance — under 0.1% of a typical heat sink assembly, and it raises surface emissivity from about 0.05 to 0.85–0.9, which improves radiation cooling far more than the film costs. The problem is location, not thickness.
One caveat worth printing: ASTM B209 and B221 do not specify thermal conductivity at all. They specify chemistry, temper and mechanical properties. Any conductivity number you see is a handbook or test value, typically 165–180 W/m·K for 6061-T6 at 25 °C, and it moves with temper. Do not put it on a purchase order as an acceptance criterion — put the temper there instead, because that is what a certificate can actually verify.
Automation components, Structural parts and Electronic housings each break a different rule
The grade that suits one of these three is often the wrong grade for the next, and the constraint that decides it is rarely the one printed on the purchase order. These are the three questions we end up asking.
Lightweight is a specification. High strength-to-weight ratio is a bill.
LME aluminum closed August 2026 at roughly $3,280 per tonne, up about 29% year on year, after touching $3,651 in May — the highest since 2022. China’s 45-million-tonne capacity cap is now fully utilized at around 45 Mt of a 73.8 Mt global total, so the supplier that absorbed every previous demand increase has no room left. US Midwest premiums sit at $485–620 per tonne on top under Section 232, and the EU CBAM took effect in January 2026. Every layer below is a negotiation, not a given.
Certificates and incoming verification for aluminum stock
Aluminum has one substitution problem that outranks all others: a bar of 6061-T6 and a bar of 6061-T4 look identical from the outside and behave nothing alike. The temper is what you are buying, and the only way to know you got it is the paperwork plus a hardness check. XS Precision issues both as standard.
The substitution you should test for. A T6-temper bar sold as T4, or a 6061 bar sold as 6082, will pass a visual inspection and dimension check every time. The two checks that catch it are a hardness test on the incoming lot and a mill certificate at 3.1 level. XS Precision runs a hardness check on every aluminum delivery, and where the customer’s end use is safety-related we will send the cut-off to a third-party laboratory for full spectrographic confirmation against the heat number before the job is released.
All three of these reach the machine shop before anyone notices
All three are caught for free at quotation stage and cost money once the material is on the floor. XS Precision reviews every incoming aluminum drawing for temper, standard and grade fit before releasing a price — say the word and we will flag anything that looks wrong before you commit.
The six questions we field most often about Aluminum Alloys
These arrive on nearly every aluminum enquiry, usually in this order. The answers below are the ones we would give on the phone, including the ones that lose us the job. XS Precision machines all three grades in the same cell, so the comparison is from our own cycle times rather than a datasheet.
6061 or 6082 — which should be on the drawing?
If your customer’s drawings are American, or you want the widest choice of stock sizes and tempers, 6061. If they are European, or the part is a structural member in thick section, 6082 — it carries 8–12% more strength there and resists coastal corrosion better because it has essentially no copper. For a simple bracket that never sees salt, the two are interchangeable in practice and you should buy whichever is cheaper in the size you need.
Can I use 7075 instead of steel to save weight?
Often yes, and it is the most satisfying substitution on this page: 7075-T6 at 570 MPa tensile is approaching many structural steels at one third of the density. Two conditions. First, the design must actually be strength-limited — if it is deflection-limited, 7075 has the same modulus as 6061 and buys you nothing. Second, nothing may be welded, and the part must either be dry or specified in T73/T7351 for chloride service.
Why did my anodized parts come back out of tolerance?
Because anodizing adds material. A Type II coating of 20 µm grows the surface by 20 µm on every face, so a shaft gets 40 µm larger in diameter and a bore gets 40 µm smaller. Type III hard anodize can be 115 µm. For anything with a fit, either machine to allow for the coating and state the allowance on the drawing, or mask the critical surfaces. We ask which fits are functional before we send parts to the anodizer.
Do we need to worry about galvanic corrosion?
Yes, and it is usually caused by the fastener rather than the aluminum. Aluminum is anodic to stainless steel and to most plated fasteners, so in a wet or salty environment the aluminum becomes the sacrificial anode around every screw hole. Use zinc-plated or aluminum-compatible fasteners, apply a sealant or a nylon washer at the joint, and keep the anodized finish intact around the hole. Anodizing is an electrical insulator, which helps here — and hurts when you needed the joint to be conductive for grounding.
What tolerance can you hold on a thin aluminum wall?
For a wall over 2 mm on a part we can support properly, ±0.02 mm on a linear dimension and ±0.05 mm on flatness is routine. Below 1 mm the material starts behaving like a spring: cutting force deflects it away from the cutter, the tool rubs, heat builds, and the wall moves again when the clamps come off. If a thin wall is unavoidable we reduce radial engagement, use a high-helix cutter, add sacrificial supports and accept a longer cycle time.
What do you need from me to quote aluminum accurately?
A STEP file; the alloy, temper and product standard written together — for example “6061-T651 per ASTM B209”; the surface finish and whether it is functional or cosmetic; which fits are critical and whether any of them will be anodized; and the quantity with its repeat pattern. The temper and the finish are the two answers that change a quote most, and they are the two most often left off the drawing.
Related capability and material pages to read next
Send the drawing. We will tell you whether the alloy and the temper match the job.
Tell us the alloy and temper as your customer wrote them, what the part has to do, whether anything is welded, whether anything is anodized, and how much mass actually matters. If 6061-T6 is enough we will say so even when the drawing asks for 7075 — and if the drawing asks for 7075 in a temper that will crack in service, we will say that too.