Guides / Materials

6061 Against 6063: Which Alloy Your Case Should Use

September 21, 2026

Nearly every aluminium keyboard case on the market is one of two alloys. Both are 6000 series, both contain magnesium and silicon, and the difference between them decides how your colour comes out. It is worth ten minutes.

The composition difference, and why it matters

6061 contains roughly 0.4 to 0.8 percent silicon and up to 0.4 percent copper. 6063 contains roughly 0.2 to 0.6 percent silicon and almost no copper.

That is the whole story, and it propagates into everything else. Silicon and copper do not convert into clear aluminium oxide during anodising. They stay in the layer as particles, scattering light and putting a grey haze over whatever dye you use.

Colour

6063 is the anodising alloy. The oxide comes out clearer and more even, colours are brighter, and the film is typically 10 to 15 percent thicker for the same process. Pastels, saturated blues and reds, and anything where the customer will compare two cases side by side all favour 6063.

6061 anodises perfectly well, it just anodises slightly cooler and duller. On a black or a dark grey nobody will ever notice. On a mint green or a coral it is the difference between the colour in your render and a colour you will be explaining in a Discord thread for six months.

Stiffness

This is where 6061 wins, and the margin is real. 6061-T6 yields around 276 MPa. 6063-T5 yields around 214 MPa, roughly 40 percent lower.

For most keyboard cases that gap does not matter. A closed box 4 mm thick in either alloy is far stiffer than anything a typist will apply to it. It starts to matter when you are designing a deliberately thin shell, a long unsupported top frame on a full size board, or a leaf spring arm that has to flex a known amount and return.

If your design has flexure features, model them for the alloy you are actually buying. A leaf spring tuned in CAD for 6061 will behave differently in 6063.

Machining behaviour

6061 is harder and tends to produce long, stringy chips that wrap around the tool and the part. Shops manage this with chip breakers and coolant strategy, but it is a nuisance on a long pocketing operation and it occasionally leaves a witness mark on a cosmetic face.

6063 is softer and more plastic. Chips break shorter and cleaner. Against that, softer metal marks more easily during handling between operations, so a shop that is careless with fixtures and trays will scratch 6063 more often than it scratches 6061.

Neither of these is a reason to pick an alloy on its own. They are a reason to ask a shop which one it prefers to run and why, because the answer tells you something about how much keyboard work it has actually done.

Availability

6061 is everywhere, in every thickness, from every stockist, in every country. 6063 is common but it is an extrusion alloy first, so plate and thick billet stock can take longer to source in some markets and some sizes.

If your schedule is tight and your shop tells you 6063 plate is four weeks out, that is not an excuse, it is a real constraint. Ask early, because material lead time is part of your schedule whether you planned for it or not.

The rule

Use 6063 when colour is the selling point of the board and the geometry is conventional.

Use 6061 when the design has thin walls, long spans or flexure features, when you want a dark or neutral colour where the difference will not show, or when availability decides it.

Use one of them for every part that has to match. That rule outranks both of the others.

What to write on the drawing

State the alloy and the temper, not just the number. “6063” alone tells a shop nothing about whether you want T5 or T6, and those behave differently. Write “6063-T5” or “6061-T6” and put the same designation on every drawing in the package.

Then add a note that the alloy may not be substituted without written approval. Substitution is not usually anyone trying to cheat you. It is a purchasing clerk finding the right thickness in the wrong alloy on a Tuesday and solving a problem nobody told them was a colour problem.

The alloy is one decision in our guide to keyboard case materials.

When the alloy is settled and the rest of the CAD package is ready, send it for quotes.

Frequently asked questions

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