Aluminum CNC Machining: Properties, Alloys and Best Practices
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Introduction
Aluminum is the most commonly machined metal — and for good reason. It's lightweight, corrosion-resistant, machines beautifully, and costs a fraction of steel or titanium. But not all aluminum is the same. Choosing the wrong alloy or finish can compromise your part's performance.
This guide covers everything you need to know about aluminum CNC machining.
1. Why Aluminum for CNC Machining?
| Advantage | Why It Matters |
|---|---|
| **Excellent machinability** | High cutting speeds, low tool wear, lower cost |
| **Lightweight** | 2.7 g/cm³ vs 7.85 for steel — 65% lighter |
| **Corrosion resistant** | Natural oxide layer protects without coatings |
| **High strength-to-weight** | 7075-T6 rivals mild steel strength |
| **Thermal conductivity** | Excellent for heat sinks and cooling |
| **Cost-effective** | Raw material is affordable and widely available |
| **Anodizable** | Decorative + protective surface treatment |
| **Recyclable** | Environmentally friendly choice |
2. Common Aluminum Alloys for CNC Machining
6061-T6: The All-Purpose Workhorse
The most popular aluminum alloy for machining.
| Property | Value |
|---|---|
| **Tensile Strength** | 310 MPa (45 ksi) |
| **Yield Strength** | 276 MPa (40 ksi) |
| **Hardness** | 95 HB |
| **Machinability** | Good |
| **Weldability** | Excellent |
| **Corrosion Resistance** | Very Good |
| **Anodizing** | Excellent |
Best For: General engineering, frames, brackets, automotive parts, consumer products, electronic enclosures
Not Ideal For: High-stress aerospace structures, high-wear applications
7075-T6: The Aerospace Standard
Significantly stronger than 6061, comparable to mild steel.
| Property | Value |
|---|---|
| **Tensile Strength** | 572 MPa (83 ksi) |
| **Yield Strength** | 503 MPa (73 ksi) |
| **Hardness** | 150 HB |
| **Machinability** | Fair (more abrasive on tools) |
| **Weldability** | Poor |
| **Corrosion Resistance** | Fair (higher copper content) |
| **Anodizing** | Good (but less uniform than 6061) |
Best For: Aircraft structures, high-stress components, competition bicycles, rock climbing equipment, molds
Not Ideal For: Welded assemblies, applications needing high corrosion resistance, decorative anodizing
2024-T3: High Strength, High Fatigue
Popular in aerospace for its excellent fatigue resistance.
| Property | Value |
|---|---|
| **Tensile Strength** | 470 MPa (68 ksi) |
| **Yield Strength** | 325 MPa (47 ksi) |
| **Machinability** | Good |
| **Corrosion Resistance** | Poor (often Alclad coated) |
| **Fatigue Resistance** | Excellent |
Best For: Aircraft fuselage, wing skins, structural components under cyclic loading
5052-H32: Marine Grade
Excellent corrosion resistance, especially in saltwater.
| Property | Value |
|---|---|
| **Tensile Strength** | 228 MPa (33 ksi) |
| **Formability** | Excellent |
| **Corrosion Resistance** | Excellent (marine) |
| **Machinability** | Fair (gummy) |
Best For: Marine components, fuel tanks, sheet metal enclosures, chemical equipment
6063-T6: Architectural Grade
Better surface finish and anodizing response than 6061.
| Property | Value |
|---|---|
| **Tensile Strength** | 241 MPa (35 ksi) |
| **Surface Finish** | Excellent |
| **Anodizing** | Excellent (best cosmetic response) |
| **Strength** | Lower than 6061 |
Best For: Architectural extrusions, decorative parts, furniture, consumer products
Alloy Selection Quick Guide
| If You Need… | Choose |
|---|---|
| General purpose, good all-around | 6061-T6 |
| Maximum strength | 7075-T6 |
| Fatigue resistance | 2024-T3 |
| Marine/corrosion environment | 5052-H32 |
| Best cosmetic anodizing | 6063-T6 |
| Lowest cost | 6061-T6 |
| High-temperature | 6061 (up to ~200°C) |
3. Aluminum Temper Designations
Aluminum alloys have temper designations that indicate heat treatment and work hardening:
| Temper | Meaning | Effect |
|---|---|---|
| **-F** | As-fabricated | No special treatment |
| **-O** | Annealed | Softest condition |
| **-T3** | Solution treated, cold worked, naturally aged | High strength |
| **-T4** | Solution treated, naturally aged | Moderate strength |
| **-T6** | Solution treated, artificially aged | Highest strength (most common) |
| **-T651** | T6 + stress-relieved by stretching | Reduced warping during machining |
4. Aluminum Anodizing Guide
Anodizing is an electrochemical process that thickens aluminum's natural oxide layer, improving durability and enabling color.
Type II vs Type III Anodizing
| Feature | Type II (Decorative) | Type III (Hardcoat) |
|---|---|---|
| **Thickness** | 5-25 μm (0.0002-0.001") | 25-150 μm (0.001-0.006") |
| **Hardness** | 200-400 HV | 400-600 HV |
| **Wear Resistance** | Moderate | Excellent |
| **Color Options** | Full range (clear, black, red, blue, gold…) | Limited (dark gray, black, olive) |
| **Dimensional Change** | ~50% of thickness added | ~50% of thickness added |
| **Cost** | $ (affordable) | (2-3× Type II) |
| **Applications** | Consumer products, enclosures | Aerospace, military, wear surfaces |
Anodizing Design Tips
- **Threaded features**: Account for coating buildup (may need post-anodize chasing)
- **Sharp corners**: Anodize builds up thinner on sharp edges
- **Masking**: Conductive surfaces (grounding points) can be masked
- **Weld zones**: Weld areas anodize differently — visible if cosmetic
5. Aluminum Machining DFM Tips
Wall Thickness
- **Minimum**: 0.5mm for small features, 1mm recommended
- **Optimal**: 2-5mm for structural walls
Tool Radii
- Design internal corners with radii ≥ 3mm when possible
- Match to standard end mill diameters
Threads
- Use coarse threads in aluminum (fine threads can strip)
- Helicoil inserts recommended for frequently disassembled threads
- Minimum thread engagement: 2× diameter for aluminum
Thin Features
- Thin ribs and tall, thin walls will vibrate during machining
- Height-to-thickness ratio should not exceed 8:1 without special fixturing
6. Cost Factors for Aluminum Machining
| Factor | Impact on Cost |
|---|---|
| **Alloy choice** | 6061 is cheapest; 7075 costs 20-30% more |
| **Part complexity** | More setups = higher cost |
| **Tolerances** | Tight tolerances slow machining speed |
| **Anodizing** | Type II adds ~15%; Type III adds ~30%+ |
| **Quantity** | 10+ parts — significant per-part savings |
| **Stock size** | Near-net-shape stock reduces machining time |
Get Your Aluminum Parts Machined
At Leland CNC, aluminum is what we machine most. We stock 6061-T6, 7075-T6, and other alloys for rapid turnaround. Send your CAD file and get a quote in 24 hours.
Published: July 2026 | Leland CNC — Precision Manufacturing Since 2009