6061 vs 6063 Aluminum: Machining vs Extrusion
Strength, machinability, extrudability, anodizing, and the selection rules — why these two 6xxx alloys almost never compete for the same part.
IsoCNC Engineering Team
CNC Machining & DFM Engineers · Updated · 6 min read
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The 30-Second Answer
Both are 6xxx-series Al-Mg-Si heat-treatable alloys, but they were bred for different processes. 6061 is the structural and machining alloy — stronger (310 vs ~210–260 MPa tensile in T6), the default for CNC parts and load-bearing anything. 6063 is the extrusion alloy — weaker but flows through complex thin-wall dies at speed and anodizes to a brighter cosmetic finish, which is why architectural profiles are made of it. Machined part? 6061. Extruded profile? 6063. The exceptions follow below.
The Numbers, Side by Side
| Property | 6061-T6 | 6063-T6 | 6063-T5 |
|---|---|---|---|
| Tensile strength | ~310 MPa | ~210–260 MPa | ~145 MPa |
| Yield strength | ~276 MPa | ~170 MPa | ~110 MPa |
| Machinability | Excellent | Good | Good |
| Extrudability | Good | Excellent — the benchmark | Excellent |
| Cosmetic anodizing | Good | Excellent — brighter, more uniform | Excellent |
| Typical form | Plate, bar, forgings | Extrusions | Extrusions |
| Typical use | Machined structural parts | Structural extrusions | Architectural/cosmetic profiles |
The strength gap — roughly a third — is the headline. Everything else is process fit.
Machining: 6061's Home Turf
6061-T6 is the reference machining aluminum: hard enough to cut cleanly, chips that break, tolerances that hold. 6063 machines acceptably — it is soft, slightly gummier, and needs sharp tools — but nothing about it rewards the machinist. Its strengths (die flow, surface brightness) are invisible on a milled part, and its weakness (a third less strength) is not. When a drawing calls 6063 for a fully machined part, it usually inherited the callout from an extrusion ancestor or an architectural habit — expect your supplier to ask.
Where 6063 legitimately meets the machine shop: secondary machining of extrusions. Drill the holes, mill the slots, tap the ends of a 6063 profile — that is normal, efficient, and exactly how extruded enclosures and frames get finished.
Extrusion and Anodizing: 6063's Home Turf
Extrusion rewards flow, and 6063 flows: its leaner chemistry pushes through complex, thin-walled dies faster, with less die wear and a better as-extruded surface than 6061. That is why the entire architectural aluminum industry — window frames, trim, channels, heatsinks with fine fins — runs on 6063 and its near cousins.
The same chemistry makes it the cosmetic anodizing champion: brighter, more uniform, more consistent color than 6061. For visible anodized profiles, 6063 is the professional default. For machined cosmetic parts the calculus flips back — 6061 anodizes well enough that its machining and strength advantages win, as covered in our anodizing guide. And for the higher-strength aluminum decision, see 6061 vs 7075.
Selection Rules We Apply on RFQs
CNC machined part from plate or bar? 6061-T6. Strength, machinability, availability.
Extruded profile, especially thin-wall or cosmetic? 6063-T5/T6. The extrusion industry's default for a reason.
Extrusion that carries real structural load? 6061 extrusion — slower to produce, stronger in service.
Show-surface anodized profile? 6063. Brighter and more uniform.
Fully machined part with a 6063 callout? Expect a question — that combination almost always deserves 6061. Send the drawing and we will quote both when it is close.
FAQ
Can you CNC machine 6063 aluminum?
Yes — it machines fine. The question is rarely “can” but “why”: 6063's advantages (extrudability, cosmetic anodizing) do not help a machined part, and its lower strength (roughly 210–260 MPa tensile in T6) gives up a third of 6061-T6's capability for no machining benefit. If the part is milled or turned from solid, 6061 is almost always the right call. If the part is an extrusion that gets secondary machining, 6063 makes sense.
Which is stronger, 6061 or 6063?
6061 by a wide margin. 6061-T6 runs about 310 MPa tensile and 276 MPa yield; 6063-T6 manages roughly 210–260 MPa tensile and around 170 MPa yield, and the common T5 temper is lower still (about 145 MPa tensile). For any load-bearing machined part, that gap settles the choice before any other property is discussed. And if you are ordering 6061 plate, the T6 vs T651 temper choice affects how flat the part stays after machining.
Why is 6063 used for extrusions instead of 6061?
Because it flows. 6063's leaner chemistry extrudes at higher speeds, through more complex and thinner-walled dies, with a better as-extruded surface — and it anodizes to a brighter, more uniform cosmetic finish. That is why window frames, architectural trim, and cosmetic profiles are 6063 territory. 6061 extrudes too, but slower, with more die wear, and is chosen when the extrusion must carry structural load.
Which anodizes better, 6061 or 6063?
6063 for cosmetics. It produces a brighter, more uniform anodized finish, which is why visible architectural and consumer profiles default to it. 6061 anodizes well — better than most alloys — but for a show-surface part, 6063 is the safer canvas. For machined cosmetic parts, the usual answer is still 6061: its machining and strength advantages outweigh 6063's modest anodizing edge.
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Send the Drawing, We Will Confirm the Alloy
Engineer review on every quote: if the alloy on your drawing fights the process your part needs, we will say so — with alternatives priced. Typically within 1–2 business days.