Aluminum selection
6061-T6 and 7075-T6 are the two aluminum grades most CNC parts are specified in. The short answer: 6061 for most machined parts, 7075 when strength or weight matters more than corrosion resistance and finish.
The short answer
| 6061-T6 | 7075-T6 | |
|---|---|---|
| Tensile strength | ~310 MPa | ~570 MPa |
| Machinability | Excellent | Good, but gummier and more prone to distortion |
| Corrosion resistance | Very good | Fair; needs anodising or coating |
| Anodising | Clear, black and colours; uniform | Anodises, but colour can be less uniform |
| Weldability | Good | Poor |
| Relative material cost | Lower | Higher |
| Typical use | Housings, brackets, plates, fixtures | Aerospace brackets, high-load parts, knife liners |
Typical values for T6/T651 temper. Always design to the mill certificate and the drawing, not to a generic table.
Where 6061 wins
6061-T6 is the default for a reason. It machines cleanly, holds a thread, anodises evenly, welds, and is available in plate, bar and extrusion. For enclosures, base plates, brackets, heat sinks and fixtures, 6061 is usually the lowest-risk choice. If your part is cosmetic and anodised, 6061 also gives the most predictable colour.
The exception is a part that is mostly a flat plate with large pockets: 6061 plate can move when you remove a lot of material. That is a geometry problem, not a grade problem, and it is solved with a stress-relieved plate or a different cut sequence.
Where 7075 wins
7075-T6 is roughly 1.8× the tensile strength of 6061. It is the right choice when the part is load-bearing and weight matters — aerospace brackets, racing components, high-stress knife liners, and fixtures that cannot deflect. It machines well if the cutter is sharp and the coolant is directed at the cut, but it is less forgiving: thin sections distort more, and the surface can tear if the tool rubs.
7075 is not the grade for a part that lives outdoors without a coating. Its copper content lowers corrosion resistance, especially at cut edges. If the part will see salt water or a wet environment, specify 6061, 5083 or 6082, or plan for anodising and a sealed edge.
Anodising and finish
Both grades anodise, but the result differs. 6061 takes clear, black and colour anodising evenly. 7075 can show a darker, less uniform finish because of its alloying elements, and the difference is more visible on large flat faces. If the part is cosmetic, send a sample or a finish reference before the run; we will return a coupon for approval.
Cost
7075 usually costs more per kilogram and machines slower, so the part price is higher for two reasons. On a small bracket the difference may be a few dollars; on a 5 kg plate it can be significant. If the strength is not needed, 6061 is the cheaper route — and often the better one.
What we would choose
- Enclosure, bracket, plate, fixture: 6061-T6.
- High-load aerospace or racing part: 7075-T6, with a coating plan.
- Marine or wet environment: 5083 or 6061, not 7075.
- Cosmetic anodised part: 6061-T6, with a finish coupon.
- Thin wall, large pocket: stress-relieved 6061 plate, or a design change; the grade alone will not fix it.
If you are between grades, send the drawing and the load case. We will tell you which one we would machine and where the risk is. Aluminum CNC machining services · aluminum material data · custom CNC parts.
Written by the engineering team at GY Machining, Dongguan. We machine prototypes and production parts in aluminum, stainless, titanium, brass and engineering plastics.