Aluminum CNC Machining: Complete 2026 Guide (Alloys, Cost, Finishes)
Engineer's guide to CNC machining aluminium: 6061 vs 7075 vs 2024, machinability, anodising, cost ranges, lead times and design tips. Written by a working CNC shop.
15 min read
Aluminium is the workhorse of CNC — about 70% of JLYPT's industrial work runs on some grade of aluminium. This guide is the deep dive: which alloy for which job, what tolerances are realistic, what finishes work, and what it actually costs.
Why aluminium dominates CNC
Aluminium hits a sweet spot of properties no other commodity material matches:
- Light — about 1/3 the density of steel (2.7 g/cm³ vs 7.85). Critical for aerospace, drones, robotics.
- Strong enough — 6061-T6 yields at 276 MPa, comparable to many mild steels.
- Cuts fast — soft enough to remove material at 3–5× the rate of stainless or titanium.
- Anodises beautifully — every colour, hard surface, integral to the part.
- Conducts heat — ideal for heat sinks, electronics enclosures, LED housings.
- Corrosion-resistant by default — the natural oxide layer protects without coating.
- Recyclable — chips and offcuts have real scrap value, lowering net cost.
Alloy comparison — which one and why
| Alloy | Yield (MPa) | Machinability | Anodise | Best for | Cost |
|---|---|---|---|---|---|
| 6061-T6 | 276 | Excellent (3-rated) | Yes — perfect | Default for 70% of work | 1.0× |
| 6063-T5 | 215 | Excellent | Yes — best cosmetic | Extruded profiles, decorative | 1.05× |
| 7075-T6 | 503 | Good (4-rated) | Acceptable, mottled | Aerospace, motorsport, structural | 1.4× |
| 7075-T651 | 503 | Good | Acceptable | Stress-relieved 7075 for stable parts | 1.5× |
| 2024-T351 | 345 | Good | Poor (clad recommended) | Aerospace skins, fatigue parts | 1.3× |
| 5052-H32 | 193 | Excellent | Yes | Marine, sheet-metal-style folded | 1.0× |
| 5083 | 215 | Good | Yes | Marine welded structures | 1.2× |
| MIC-6 / Cast tool | 170 | Excellent | Yes (cosmetic mediocre) | Vacuum chucks, optical bases, jigs | 1.6× |
| A380 die-cast | 160 | Tricky (porosity) | Difficult | Cast housings (cnc finishing only) | 0.9× |
When 6061 is the right choice
- General-purpose brackets, housings, plates.
- Anything that needs cosmetic anodising.
- Cost-sensitive work where strength is moderate.
- Welded assemblies (6061 welds well).
When 7075 is worth the upgrade
- Structural aerospace components (wing ribs, frames).
- High-stress brackets that fail in 6061 testing.
- Motorsport (fewer parts means weight matters more).
- Where 80%+ more strength justifies the 40% cost.
Machinability and cycle times
Aluminium machines fast — but how fast depends on alloy choice and tooling. Indicative cycle times for a representative 50×50×25 mm bracket with moderate complexity:
| Alloy | Roughing speed | Finishing speed | Tool life | Total cycle (typical) |
|---|---|---|---|---|
| 6061-T6 | Very fast | Very fast | Long | 8 min |
| 7075-T6 | Fast | Fast | Medium | 11 min |
| 2024 | Fast | Fast | Medium | 12 min |
| MIC-6 (cast tool plate) | Fast | Excellent | Long | 9 min |
| Stainless 316L (compare) | Slow | Slow | Short | 38 min |
Achievable tolerances on aluminium
| Feature | Standard CNC | Precision CNC | High-end (with care) |
|---|---|---|---|
| External dimensions | ±0.10 mm | ±0.025 mm | ±0.005 mm |
| Hole diameter (drilled) | ±0.05 mm | ±0.013 mm | ±0.005 mm |
| Hole diameter (reamed) | ±0.013 mm | ±0.005 mm | ±0.0025 mm |
| Surface finish (Ra) | 3.2 µm | 0.8 µm | 0.4 µm |
| Flatness (over 100 mm) | 0.05 mm | 0.013 mm | 0.005 mm |
| Concentricity / true position | 0.05 mm | 0.025 mm | 0.013 mm |
Aluminium's thermal expansion (~23 ppm/°C) is roughly twice that of steel — so for ±0.005 mm tolerances on parts longer than 100 mm, JLYPT machines in a temperature-controlled cell. See our tolerances and GD&T guide for more.
Finishes that work on aluminium
Common — fast, cheap
- As-machined + deburr — bare metal, lowest cost.
- Bead blast — uniform matte texture, hides tool marks.
- Type II anodise (decorative) — clear, black, blue, red, gold etc.
- Brush finish — directional grain like appliance steel.
Premium — performance
- Type III hard anodise — 60 HRC surface, wear resistance.
- Chromate conversion (Alodine) — corrosion + paint primer.
- Powder coat — thick, durable, any colour.
- Electroless nickel plate — wear + uniform thickness.
Industry applications
- Consumer electronics — laptop chassis, phone frames, camera bodies. 6061 + Type II anodise dominates.
- UAV and drones — frames, motor mounts, gimbals. 7075 for structural, 6061 for non-critical. See UAV parts.
- Aerospace — brackets, instrumentation housings, ground support. 7075 + 2024 dominate. See aerospace manufacturing.
- Robotics — joint housings, drive arms, gripper bodies. 6061 + hard anodise common. See robotic parts.
- Heat sinks & LED housings — 6061 or 6063 for thermal conductivity, anodised black for emissivity.
- Optical & imaging — MIC-6 cast tool plate for dimensional stability over time.
- Automotive prototypes — 7075 for race-car components, 6061 for OEM-grade prototypes.
Real cost ranges
Indicative pricing for a typical 50×50×25 mm aluminium bracket, anodised type II, batch quantities:
| Quantity | 6061 unit cost | 7075 unit cost | Per-unit drop |
|---|---|---|---|
| 1 (prototype) | $95 | $130 | — |
| 10 | $28 | $42 | −71% |
| 100 | $11 | $18 | −61% |
| 1000 | $6.20 | $10 | −43% |
Want to lower your aluminium part cost without redesigning? See our cost reduction guide — typical savings: 20–40% by relaxing tolerances, switching from 7075 to 6061 where possible, and consolidating setups.
Design tips that save money on aluminium
- Internal corner radii ≥ 1 mm — lets us use larger, faster end mills.
- Wall thickness ≥ 0.8 mm — thinner walls deflect during cutting.
- Use 6061 unless you have a strength reason to upgrade — saves 30–40% on material + machining.
- Specify Type II anodise unless hardness is required — Type III roughly doubles finish cost.
- Don't demand mirror polish on cosmetic surfaces — bead blasting before anodising looks great and costs less.
- Tolerance only critical features — use ISO 2768-mK default for non-mating dimensions.
- Add 0.3 mm chamfers to all external edges — eliminates manual deburring labour.
- Avoid pockets deeper than 4× tool diameter — deep pockets need slow finishing passes.
Frequently Asked Questions
- 6061-T6 by a wide margin — about 70% of CNC aluminium work uses it. It machines fast, anodises beautifully, has good strength (276 MPa yield), and bar stock is inexpensive. Switch to 7075 only when strength testing demands it.
- Yes, but cosmetic results are noticeably worse — slightly mottled or non-uniform colour, especially on dark colours. For structural 7075 parts where appearance matters, consider chromate conversion (Alodine) instead, or accept the cosmetic trade-off.
- ±0.005 mm is achievable on production-grade equipment with care. Standard work holds ±0.025 mm easily. Aluminium is actually easier to hold tight tolerances on than steel because it doesn't spring back during cutting.
- Yes — even bare aluminium forms a self-healing oxide layer that resists most outdoor environments. For aggressive environments (marine, industrial), Type II or Type III anodising adds significant protection. 5052 is the marine-grade choice.
- 6061 and 5052 weld well (TIG). 7075 is essentially un-weldable — it loses 50%+ strength at the weld. If you need a welded assembly, design for 6061 from the start.
- Material: 7075 bar stock is roughly 40% more expensive than 6061. Machining: 7075 cuts ~25% slower, adding labour. Net total cost: 7075 finished parts run ~50% more than the 6061 equivalent.
- Yes — we stock MIC-6 in common thicknesses (12 mm, 25 mm, 50 mm). It's our default for vacuum chucks, optical bases, and jigs requiring dimensional stability. See our CNC services.
- Aluminium wins for strength (200+ MPa vs 50–100 for engineering plastics), thermal conductivity, and durability. Plastics win for weight (~half the density), insulation, and lower cost. For load-bearing parts, aluminium almost always — see our material selection guide.
What is the most common aluminium alloy for CNC machining?
Can I anodise 7075 like 6061?
How tight a tolerance can you hold on aluminium?
Is aluminium good for outdoor use?
Can you weld machined aluminium parts?
What's the cost difference between 6061 and 7075?
Can JLYPT source MIC-6 cast tool plate?
How does aluminium compare to plastic CNC parts?
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About the author
JLYPT Engineering Team
Senior CNC Application Engineers
Our application engineering team brings 15+ years of combined experience producing precision components for aerospace, medical, robotics and industrial automation customers.
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