Aluminum 6061 vs Brass C360 for CNC Machining (2026)

Choosing between Aluminum 6061-T6 and Brass C360 (free-cutting) for CNC parts isn’t about naming a single “best” material. It’s about understanding how each behaves on the machine and in service—then matching those traits to your part’s requirements. Think of it like selecting the right bit from your toolbox: both are excellent, but they shine in different jobs.

Key takeaways

• Weight and strength: 6061-T6 offers high specific strength at roughly one-third the density of brass—ideal for weight-sensitive parts.

• Machinability: C360 is the benchmark for machinability (rated ~100% among brasses), enabling tight tolerances and near-mirror as‑machined finishes with low tool wear.

• Surface finish and tolerances: 6061 usually hits Ra ≤1.6 μm with good setups; C360 commonly delivers Ra as low as 0.4–1.6 μm and tight turned tolerances.

• Corrosion and environments: 6061 has good general resistance and anodizes well; C360 is fine in benign environments but avoid chloride/marine exposure without choosing specialized brasses.

• Thermal/electrical: Both conduct heat and electricity well enough for many designs; 6061 tends to have higher thermal conductivity, while C360 provides adequate conductivity for lots of connectors.

• Regulatory: Standard C360 contains ~3% lead, restricting use in potable-water and some RoHS/REACH contexts—consider low‑lead/DZR brasses or 6061 where applicable.

  
  

Aluminum 6061 vs Brass C360: Quick Comparison

Composition and core properties

Aluminum 6061-T6 — definition and properties

6061 is a heat‑treatable Al‑Mg‑Si alloy. The T6 temper (solution heat‑treated and artificially aged) delivers a strong balance of strength, corrosion resistance, and machinability. Typical ranges used by engineers: ultimate tensile ≈290–310 MPa (≈42–45 ksi), yield ≈240–276 MPa (≈35–40 ksi), elongation ≈8–12%, density ≈2.70 g/cm³. Industry overviews note 6061’s suitability for structural components and anodizing response, consistent with common handbook values.

Brass C360 (UNS C36000) — definition and properties

C360 is a free‑cutting brass with Cu ~60–63%, Zn ~34–37%, and Pb ~2.5–3.7% to promote chip break and machinability (the benchmark “100%” machinability reference among brasses). Typical property bands: ultimate tensile ≈350–500 MPa, yield ≈200–345 MPa, elongation ≈25–50%, density ≈8.4–8.6 g/cm³, electrical conductivity ≈26–29% IACS, thermal conductivity ≈120–125 W/m·K. These align with Copper Development Association (CDA) summaries and standard materials databases.

Density and weight implications

6061 parts weigh about one‑third as much as brass for the same volume. If you’re designing a drone bracket, handheld housing, or any part where mass matters, aluminum’s low density is a major advantage. Brass’s higher density can be desirable when heft and perceived quality are a feature (e.g., premium knobs and decorative hardware) and can improve damping in some assemblies due to higher stiffness and mass.

Machinability and tool behavior

6061‑T6 machines readily but can develop built‑up edge (BUE) without the right cutter geometry and coolant strategy. High‑helix, polished carbide tools (often with aluminum‑friendly coatings like ZrN or DLC) and consistent chip evacuation reduce BUE and improve finish.

C360 is famous for short, well‑broken chips, stable cutting forces, and very low tool wear, enabling aggressive feeds/speeds and excellent surface quality—ideal for high‑volume turned components and fine features.

• Starting points (validate on your machine):

• 6061 milling (carbide): ≈250–600 SFM with chip load ≈0.002–0.006 in/tooth depending on tool diameter and operation. Use toolmaker calculators to dial in exact parameters.

• C360 turning (carbide): ≈400–800 SFM; feeds ≈0.004–0.010 in/rev for roughing and ≈0.001–0.004 in/rev for finishing. Insert‑specific calculators provide precise guidance.

Tolerances and surface finish

Global manufacturing networks publish baseline tolerances for CNC metals, then review tighter requests. Hubs notes standard CNC tolerance ≈±0.125 mm (±0.005 in) with default as‑machined finish around Ra 3.2 μm (125 μin), with tighter options available.

Practical expectations on shop‑controlled setups:

• 6061: Routine ±0.01–0.05 mm is common for milled features; ≈±0.01–0.02 mm is achievable on critical features with thermal control, stable fixturing, and fine finishing passes. Ra ≤1.6 μm is straightforward; Ra ≤0.8 μm is achievable with optimized finishing.

• C360: Routine ±0.02 mm is common on turned features; ≤±0.01 mm is feasible for short features on rigid lathes. Ra ≈0.4–1.6 μm is typical with finishing passes; near‑mirror “as‑machined” is a realistic target on many geometries.

Corrosion resistance and environments

6061 offers good general corrosion resistance in atmospheric and freshwater settings and is suitable for outdoor use. In chloride‑rich marine environments, consider protective finishes—Type II or Type III anodizing per MIL‑A‑8625/MIL‑PRF‑8625—to improve durability. Industry explainers summarize thickness bands and benefits.

C360 has good general resistance but is susceptible to dezincification in chloride‑bearing waters and is not recommended for prolonged seawater/brackish service. For potable or marine exposure, designers typically choose dezincification‑resistant (DZR) or naval brasses.

Thermal and electrical conductivity

If your part needs to move heat, 6061’s thermal conductivity (≈167–170 W/m·K) is helpful for housings and heat‑spreading components. Brass C360’s thermal conductivity (≈120–125 W/m·K) and electrical conductivity (≈26–29% IACS) are often sufficient for connectors, inserts, and contact hardware, though copper‑rich alloys excel when conductivity is paramount.

Finishing options and dimensional effects

6061 anodizing

• Type II (sulfuric) and Type III (hardcoat) are common. Typical thickness bands: Type II ≈0.0001–0.0010 in; Type III ≈0.0005–0.0045 in. Dimensional change rule of thumb: about half the coating thickness builds up above the surface and half penetrates—so across a diameter, expect ≈2× the buildup per side.

For RFQs and finishing choices on aluminum, see Kaierwo’s resources: Aluminum material selection guide and CNC Machining Services.

C360 polishing and plating

• Polishing can achieve a mirror‑like finish (single‑digit μin Ra on buffed areas) but removes a small amount of material—plan fits accordingly.

• Nickel/chrome plating on brass is common for decorative and wear resistance. Typical nickel thickness ≈0.0005–0.0010 in; chrome topcoat is very thin (≈0.5–1 μm). Diameter increase is roughly twice the coating thickness—account for this in toleranced features.

Regulatory considerations: lead in C360

Standard C360 contains ~3% lead for free‑cutting performance. In the U.S., potable‑water products must meet the Safe Drinking Water Act “lead‑free” rule—a weighted average ≤0.25% lead across wetted surfaces. EPA resources explain the definition and enforcement postur. For EU RoHS/REACH contexts, specify low‑lead/lead‑free or DZR brasses—or pivot to aluminum options—based on certification needs.

Typical CNC applications

• 6061-T6: Structural brackets, frames, housings, heat sinks, drone/robotics parts, consumer enclosures, fixtures, and general‑purpose prototypes—especially where weight and corrosion resistance (with anodizing) matter.

• C360 brass: High‑volume turned parts, precision threads, inserts, bushings, valves/fittings for non‑potable service, electrical hardware and connectors, and decorative components where near‑mirror as‑machined finish is valued.

How to choose for your part

Ask yourself: What matters most—mass, finish, tolerance, environment, or compliance?

• Weight‑sensitive structural parts or heat‑spreading housings: Favor 6061‑T6; consider Type II/III anodize for durability.

• Cosmetic precision and tight threads, especially in high‑volume turning: Favor C360; expect fast cycles and superb as‑machined surfaces.

• Chloride/marine exposure or potable‑water contact: Avoid standard C360; specify DZR/naval brasses or use anodized aluminum if appropriate.

• RFQ and manufacturing strategy: Tight tolerances on thin‑wall aluminum benefit from stable fixturing and thermal control; complex geometry can justify 5‑axis machining. Explore services like CNC Machining and 5‑Axis machining to match capability to features.

Aluminum 6061 vs Brass C360 is not a winner‑takes‑all choice. Align material behavior with part goals—weight, finish, tolerance, environment, and compliance—and validate your machining parameters on the shop floor with toolmaker calculators. Then you’ll get the right part, the first time.