Oct 10, 2026CNC Machining Tips
Aluminum 6061-T6 vs 7075-T6: Which Alloy for CNC Machined Parts?
6061-T6 or 7075-T6? Compare machinability, strength, corrosion resistance and cost to choose the right aluminum alloy for your CNC machined parts.
"Aluminum" is not a specification. The two grades that dominate CNC machined parts — 6061-T6 and 7075-T6 — look similar on a shelf and behave very differently in service. Pick the wrong one and it shows up as parts that bend under load, threads that strip, anodizing that looks patchy, or a part that costs twice what it should. This guide gives you the practical differences and a selection rule you can apply in five minutes.
6061-T6: the general-purpose workhorse
6061 is an aluminum-magnesium-silicon alloy, most commonly supplied in the T6 temper — solution heat-treated and artificially aged. It offers good strength (roughly 310 MPa tensile, 275 MPa yield), excellent corrosion resistance, good machinability, easy welding and, for cosmetic parts, the most uniform anodizing of any common aluminum grade. It is also the cheaper of the two and available everywhere in plate, bar and extrusion, which keeps lead times short.
Typical applications: brackets, housings, enclosures, baseplates, panels, automation fixtures and general mechanical components — the large majority of custom machined parts.
7075-T6: the high-strength option
7075 is a zinc-based alloy, often described as comparable in strength to some steels. In the T6 temper it reaches roughly 500 MPa yield — about eighty percent higher than 6061. Those numbers matter when a part carries real load: structural brackets, high-stress fittings, robotic arms, drone components and aerospace-style applications where strength-to-weight ratio drives the whole design.
The trade-offs are real. 7075 costs more — both the material and, often, machining time. It anodizes to a darker, slightly less uniform finish. It is not recommended for welding. And its corrosion resistance is lower than 6061's, with a known concern about stress-corrosion cracking in the T6 temper for critical long-service applications.
Tempers, briefly
T6 means solution heat-treated and artificially aged — the standard high-strength condition. T651 is T6 with a controlled stretch to relieve internal stresses, used for plate that will be machined heavily; it prevents the part from distorting as material is removed. T73 is an overaging treatment that trades roughly ten percent of strength for dramatically better stress-corrosion resistance — the right choice for parts facing corrosive environments under sustained load.
Head-to-head comparison
Strength: 7075-T6 wins clearly — around 500 MPa yield against 275 MPa for 6061-T6. 7075 is slightly denser (2.81 vs 2.70 g/cm3), but its strength-to-weight ratio is still about seventy percent better. For most brackets, housings and enclosures, 6061 already has more margin than the application will ever use.
Machinability: both machine well, but 6061 is slightly easier and more forgiving. 7075's higher hardness demands more attention to tool wear and surface finish on long runs.
Anodizing and appearance: 6061 takes clear and colored anodizing beautifully and uniformly, making it the safer choice for visible parts. 7075 anodizes darker with more color variation, so it is better reserved for function-first parts.
Corrosion and environment: 6061 is more corrosion-resistant overall. For marine or long-service stress-critical parts that must use 7075, choose T73 rather than T6.
Cost and availability: 6061 is cheaper as material and usually as a finished part, and it is stocked in more sizes. Budget the 7075 route only when the strength is genuinely needed.
A five-minute selection rule
Choose 6061-T6 for brackets, housings, covers, panels, fixtures, cosmetic and anodized parts, and general mechanical components — it covers the large majority of custom parts. Choose 7075-T6 (T651 when machined from plate) for high-load structural parts where strength-to-weight ratio drives the design: robotic links, stressed fittings, loaded fixtures and aerospace-style components. If the part faces corrosive environments and must use 7075, discuss the T73 temper with your supplier. And if you are on the fence, start with 6061 and optimize the geometry — reinforcing ribs, fillets and sensible wall thickness often beat a material upgrade on both cost and stiffness.
What matters more than the alloy
In most projects the alloy is not the first variable to optimize. Wall-thickness continuity, generous internal fillets, sensible tolerances and the right surface treatment usually decide whether a part performs well and prices well. Our engineers review every drawing before quoting and will tell you when a geometry change is worth more than a material change — at no cost, before you commit to production.
Get a material recommendation with your quote
Send your drawing with the load conditions and environment — or simply a note that you are unsure — to info@prolathe.com or through the contact form. We will recommend a grade, flag anything risky in the design, and quote your CNC machined parts within 24 working hours.
Tolerances and machining notes by alloy
Both grades machine to the same tolerances — the difference is how much effort it takes. 6061-T6 holds ±0.05 mm comfortably on standard CNC turning and milling, with good surface finish straight off the tool. 7075-T6 also holds tight tolerances, but its higher hardness accelerates tool wear, so long production runs need more frequent tool changes to protect surface finish and dimensional consistency. When we quote a 7075 part, that tooling attention is part of the price difference — it is not just the material cost.
One practical note for thin walls: 7075's higher strength lets you machine thinner walls without losing load capacity, but it also distorts more readily if internal stresses are not relieved. For plate parts machined down substantially, specify 7075-T651 and discuss the machining sequence with your supplier. For 6061, walls under one millimeter are best avoided regardless of grade — stiffness, not strength, becomes the limiting factor.
Prototype or production: does the alloy choice change?
For functional prototypes, the pragmatic default is to machine in 6061-T6 even if production will run in 7075 — unless the prototype's job is specifically to validate strength or weight. A 6061 prototype arrives faster and cheaper, and it validates fit and function just as well. Move to the production alloy once geometry is locked, and re-quote, because the price difference between the two is material enough to matter at volume. The exception is cosmetic validation: if the final part will be anodized in a specific color, prototype in the production alloy and finish, since 6061 and 7075 anodize visibly differently.
Material certificates and traceability
Both grades are available with mill certificates (material test reports) that document the heat number, chemical composition and mechanical properties. If your industry requires traceability — medical, aerospace, automotive or any regulated supply chain — request certificates with the RFQ rather than after delivery. It costs nothing at quoting and avoids a paperwork scramble later. We provide certificates on request for all common aluminum, stainless and engineering-plastic materials.
