Aluminum is the most commonly machined metal in CNC manufacturing — and for good reason. It cuts quickly, holds tight tolerances, costs less than steel or titanium, and can be anodized for corrosion resistance and aesthetics. However, “aluminum” is not one material — it is a family of alloys with dramatically different properties. Choosing the wrong alloy or machining it with the wrong parameters can mean the difference between a profitable part and expensive scrap. This guide covers the aluminum alloys you will encounter in CNC machining services and how to machine each one correctly.
Why Aluminum Machines So Well
Aluminum’s exceptional machinability comes from its physical properties, allowing for high-speed production while maintaining strict CNC machining tolerances:
- Low cutting forces: Aluminum requires roughly one-third the cutting force of steel — meaning less tool deflection and faster feeds.
- High thermal conductivity: Heat is carried away by the chip rather than the tool tip, allowing for extreme cutting speeds.
- No work hardening: Unlike stainless steel, aluminum does not harden during the cut.
- Non-abrasive: Reduced tool wear compared to cast iron or stainless steel.
The Most Important Aluminum Alloys for CNC Machining
6061-T6 / 6061-T651
The universal workhorse. 6061-T6 is the standard for general-purpose structural components. It offers excellent machinability and responds well to CNC milling services for complex geometries.
- Machinability: Excellent. Surface finish Ra 0.8 µm is readily achievable.
- Anodizing: Takes Type II and Type III (hardcoat) anodizing well.
- Typical applications: Brackets, enclosures, manifolds, and prototype parts.
7075-T6 / 7075-T651
The aerospace aluminum. Strength approaching mild steel at one-third the weight. It is a preferred choice for high-stress applications, including precision machining for optics where structural stability is key.
- Yield strength: 503 MPa (73 ksi) — nearly double 6061.
- Machinability: Very good. Produces small, discontinuous chips.
- Typical applications: Aircraft structural components, drone parts, and high-stress mechanical parts.
2024-T3 / 2024-T351
High fatigue strength. Valued for its fatigue resistance, often used in aircraft skins. For cylindrical components, this alloy is frequently used in CNC turning services.
- Yield strength: 345 MPa (50 ksi).
- Corrosion resistance: Poor — typically requires cladding or coating.
- Typical applications: Fuselage skins and high-fatigue mechanical components.
5083
Marine-grade aluminum. Exceptional corrosion resistance in seawater with good weldability. Ideal for marine hardware and cryogenic tanks.
MIC-6 (Cast Aluminum Tooling Plate)
For flatness-critical parts. Cast and stress-relieved, MIC-6 stays flat during and after machining. It is commonly used for vacuum chambers and precision bases.
Common Aluminum Machining Problems and Solutions
- Built-up edge (BUE): Aluminum welds to the tool. Solution: Increase cutting speed and use polished carbide.
- Chip packing: Long chips fill flutes. Solution: Use 2- or 3-flute tools for better evacuation.
- Burr formation: Ductility causes burrs. Solution: Use sharp tools and programmed chamfer passes.
Tik Precision machines all standard aluminum alloys on our CNC mills and lathes. Whether you need 6061 prototypes or 7075 production parts, contact us for a fast, competitive quote.
