The Most Common Aluminum Alloys for Precision Turning & Milling in Contract Manufacturing
Choosing the right aluminum alloy can make or break a machined part’s cost, lead time, and in-field performance. In contract manufacturing—where volumes, designs, and end uses vary widely—the “best” aluminum depends on what you’re optimizing for: machinability, strength-to-weight, corrosion resistance, cosmetics, weldability, or regulatory compliance.
Below is a practical guide to the aluminum alloys we see most often in precision CNC turning and milling, with tips to help engineers write clearer prints and make smarter tradeoffs.
A quick orientation: series & temper matter
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Series (2xxx, 5xxx, 6xxx, 7xxx, etc.) tells you the primary alloying element and general behavior (strength, corrosion, weldability).
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Temper (e.g., T6, T651, T3, H32) tells you the heat treatment or work hardening state. It directly affects strength, stability, and machinability.
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Call out both on your print. “6061” is incomplete; “6061-T6” or “6061-T651 plate” avoids surprises in strength and flatness.
The alloys you’ll pick 80% of the time
6061-T6 / T651 — The all-around workhorse
Why choose it: Excellent balance of machinability, strength, corrosion resistance, and cost. Readily available in bar, plate, and extrusion.
Best for: General-purpose housings, brackets, fixtures, manifolds, and anodized parts.
Notes for machining: Stable and predictable; T651 (stress-relieved plate) resists movement after heavy material removal. Takes attractive clear or black anodize.
7075-T6 / T651 — High strength, aerospace favorite
Why choose it: Very high strength-to-weight and good fatigue resistance.
Best for: Structural components, high-load parts, thin but stiff sections.
Notes for machining: Machines crisply with short chips and excellent surface finish. Corrosion resistance is lower than 6xxx; not great for welding. Clear anodize tends to gray/bronze; manage cosmetic expectations or specify dye.
2024-T3 / T351 — Fatigue strength & toughness
Why choose it: Strong with excellent fatigue properties; common in aerospace.
Best for: Moving/rotating parts, load-bearing structures.
Notes for machining: Machines well but is copper-rich, so corrosion resistance is modest; usually alodined/primed/painted rather than decorative anodized. Poor weldability.
5052-H32 — Formability & corrosion resistance (sheet-centric)
Why choose it: Great for sheet parts that need bending and excellent corrosion resistance (marine, outdoor).
Best for: Enclosures, panels, formed brackets, marine hardware (when cut from sheet/plate).
Notes for machining: Softer; gummy in milling/turning compared with 6xxx/7xxx. Anodizes nicely. Excellent weldability.
5083 (various H tempers) — Marine & cryogenic toughness
Why choose it: Top-tier corrosion resistance and toughness, especially in saltwater.
Best for: Marine, pressure vessels, cryogenic components.
Notes for machining: Similar to 5052 (softer feel at the spindle); great weldability. Often specified where 6xxx won’t survive the environment.
6082-T6 — A strong, 6061-like alternative (common in EU)
Why choose it: Slightly higher strength than 6061, widely available internationally.
Best for: General machining where 6082 is the regional standard.
Notes for machining: Behaves much like 6061; good anodize response.
For speed at the lathe: free-machining aluminums
2011 (and 2007 in EU) — The automatic-screw favorite
Why choose it: Outstanding machinability, short chips, high throughput on Swiss/CNC lathes.
Best for: High-volume turned parts with threads, small diameters, tight cycle times.
Notes & compliance: Contains lead for machinability—often not RoHS compliant. Typically poor for welding/anodize cosmetics. Confirm regulatory requirements early.
6020 (lead-free alternative)
Why choose it: Free-machining behavior without lead.
Best for: Turned parts where RoHS/REACH compliance matters.
Notes for machining: Very good chip control and tool life. Better finishing and compliance story than 2011.
(You may also encounter 6262 or 6012; many variants rely on Pb/Bi for machinability. If you need RoHS compliance, specify it explicitly and consider 6020.)
Special mention: cast tooling plate (MIC-6®, ATP-5®)
Why choose it: Exceptional flatness and stability out of the box.
Best for: Vacuum plates, bases, fixtures, precision plates, and covers where flatness trumps ultimate strength.
Notes for machining: Machines easily but is cast—don’t use for structural, high-load parts. Specify flatness on datum faces; avoid heavy asymmetric stock removal that could induce movement.
Alloy selection cheat-sheet
| Alloy & Temper | Machinability | Strength | Corrosion | Weldability | Anodize Cosmetics | Common Uses |
|---|---|---|---|---|---|---|
| 6061-T6/T651 | ★★★★ | ★★★ | ★★★★ | ★★★ | ★★★★ | General milled/turned parts, fixtures |
| 7075-T6/T651 | ★★★★★ | ★★★★★ | ★★ | ★ | ★★ (dye recommended) | High-load, thin sections, aerospace |
| 2024-T3/T351 | ★★★★ | ★★★★ | ★★ | ★ | ★ (usually coated) | Rotating parts, structures |
| 5052-H32 | ★★ | ★★ | ★★★★★ | ★★★★★ | ★★★★ | Formed enclosures, marine |
| 5083 (H tempers) | ★★ | ★★★ | ★★★★★ | ★★★★★ | ★★★ | Marine, cryogenic |
| 6082-T6 | ★★★★ | ★★★★ | ★★★★ | ★★★ | ★★★★ | 6061-like applications |
| 2011 (free-machining) | ★★★★★ | ★★★ | ★★ | ★ | ★ | High-volume turned parts |
| 6020 (lead-free FM) | ★★★★½ | ★★★ | ★★★ | ★★ | ★★–★★★ | RoHS-compliant turned parts |
| MIC-6/ATP-5 (cast plate) | ★★★★ | ★★ | ★★★★ | ★★★ | ★★★★ | Precision plates, fixtures |
(Stars are relative within aluminum alloys.)
DFM notes that save time and money
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Specify temper and product form. Example: “6061-T651, plate” or “6061-T6, extruded bar.” Plate vs. bar impacts stability and flatness.
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Call out finish realistically. If you need premium cosmetics:
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Prefer 6061 or 6082 for clear/black anodize.
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Expect 7075 to tint gray/bronze under clear; black dye helps uniformity.
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Avoid decorative anodize on 2024 and free-machining grades.
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Tolerance stackup > material choice. For tight GD&T (true position, flatness, profile), consider T651 stress-relieved plate or design in stock for post-machining stress relief.
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Thin walls & small threads. High-strength alloys (7075/2024) help stiffness in thin sections, but plan for corrosion protection. For tiny threaded features on turned parts, free-machining grades (2011/6020) shorten cycle time and reduce burrs.
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Welding? Say so early. If the part will be welded, favor 5xxx or 6xxx. Avoid 2xxx/7xxx for weldments.
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Regulatory compliance. If your product must be RoHS/REACH compliant, avoid leaded free-machining grades (e.g., 2011) or explicitly allow a compliant alternative like 6020.
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Anodize color matching. For assemblies with multiple parts, specify the same alloy/temper and consolidate finishing at one shop to minimize shade variance.
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Threads & inserts. For high-cycle assembly in softer alloys (5xxx/6xxx), consider helicoils or key-locking inserts to protect threads.
Quick picks by design goal
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Best all-around: 6061-T6/T651
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Highest strength: 7075-T6/T651 (treat for corrosion; manage cosmetics)
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Best for turning throughput: 2011 (non-RoHS) or 6020 (RoHS)
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Best for formed sheet + CNC ops: 5052-H32
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Marine exposure: 5083 (then 5052), or 6061 with robust coating
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Flattest plates & fixtures: MIC-6® / ATP-5®
Learn more about Stainless Steel
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