Copper 260 vs. 360 Choosing the Right Brass
Both are brass. One machines significantly faster (100% vs. 30% machinability). The other plates better and is RoHS compliant. Here is the full comparison.
The Lead Addition Changes Everything
C260 and C360 share the same base copper-zinc system. The 3% lead addition in C360 is not a trace impurity — it fundamentally transforms the alloy from a structural and forming material into the most machinable metal in commercial use. Understanding why lead does this, and what it costs you in other properties, is the foundation for every brass alloy decision.
Alloy Chemistry and Microstructure
The composition difference between C260 and C360 is small in numbers but large in consequence.
C26000 — Cartridge Brass (70/30)
Nominal composition: 68.5–71.5% Cu, balance Zn, lead max 0.07%. The 70/30 Cu/Zn ratio places the alloy solidly in the alpha-phase field of the Cu-Zn binary diagram. Alpha-phase brass has an FCC crystal structure that enables excellent cold formability — the alloy can be cold-worked to 65% reduction in area before annealing is required.
The result: C260 deep-draws, bends, stamps, and spins well. Chips from machining are long and stringy because the ductile alpha phase does not encourage chip fracture. Machinability rating: 30%.
C36000 — Free-Cutting Brass (61.5/35.5/3Pb)
Nominal composition: 60.0–63.0% Cu, 35.5% Zn, 2.5–3.7% Pb. The higher zinc content (35.5%) causes a small amount of beta phase to appear alongside the alpha matrix. More importantly, the 3% lead is insoluble in the brass matrix at room temperature and precipitates as fine globules (1–5 µm diameter) at grain boundaries and within the alpha grains.
These lead globules act as internal lubricant and stress concentrators. Under cutting, they promote chip fracture, reduce tool-face adhesion, and enable significantly faster cycle times (100% vs. 30% machinability rating). Machinability rating: 100% — C36000 is the reference standard for copper alloys.
Why Lead Makes Brass More Machinable
Lead is insoluble in copper and brass. It precipitates as discrete globules that act as internal chip-breakers. As the cutting tool shears the workpiece, lead inclusions at the chip shear plane concentrate stress and initiate fracture, producing short chips. Lead also melts at 327°C — well below the cutting zone temperature (~200–400°C) — providing liquid lubrication at the tool-chip interface. This combination of chip-breaking and lubrication is what gives C360 its 100% machinability rating.
Mechanical Properties Comparison
Properties for the most common stock temper for each alloy. Half-Hard (H02) for rod/bar used in CNC machining.
| Property | C26000 (Cartridge) | C36000 (Free-Cut) | Winner |
|---|---|---|---|
| Cu content | 70% | 61.5% | C260 (higher Cu = better conductivity) |
| Electrical conductivity | 28% IACS | 26% IACS | C260 (marginally) |
| Thermal conductivity | 121 W/m·K | 115 W/m·K | C260 (marginally) |
| UTS (H02) | 375 MPa (54 ksi) | 385 MPa (56 ksi) | C360 slightly higher |
| Yield strength (H02) | 310 MPa (45 ksi) | 130 MPa (19 ksi) | C260 — significantly higher |
| Elongation (H02) | 23% | 18% | C260 — advantage for forming |
| Hardness (H02) | HRB 70 | HRB 78 | C360 slightly harder |
| Machinability | 30% | 100% | C360 — significantly faster (100% vs 30%) |
| Density | 8.53 g/cm³ | 8.50 g/cm³ | Equal |
| Lead content | <0.07% | 2.5–3.7% | C260 — RoHS compliant |
| Stress corrosion resistance | Good | Moderate | C260 (less zinc, no lead phases) |
| Dezincification resistance | Moderate — better than C360 but not immune | Higher risk | C260 |
Machine C260 or C360 at MakerStage
Both alloys are available for CNC machining. Upload your CAD file and get a DFM-reviewed quote — we will confirm material availability and flag any RoHS or plating considerations before production.
Get a Brass CNC Quote with Free DFM ReviewCorrosion Resistance and Plating Adhesion
Two properties that significantly favor C260 when the part will be plated or used in an aggressive environment.
Corrosion Behavior
Dezincification
Stress Corrosion Cracking
Atmospheric
Hot chloride water
Plating Adhesion
C260 is the preferred alloy for electroplated parts. Its homogeneous alpha-phase microstructure provides a uniform substrate for the plating electrolyte. Electroless nickel (ENi), silver, tin, and decorative chrome all adhere consistently to C260.
C360 can be plated but requires additional preparation. The lead-rich grain boundary phases do not plate uniformly — lead is poorly wetted by most plating solutions. Bright nickel and electroless nickel over C360 can show adhesion defects at the lead sites unless the surface is pre-treated with a bright dip in nitric/sulfuric acid to remove surface lead, followed by a copper strike before the final plate.
If your part requires electroless nickel (ENi) plating and is made from C360, specify this explicitly on the drawing and communicate to the plating shop. The lead pre-treatment adds cost and must be performed before ENi application. Without it, plating delamination at lead sites is a known quality escape.
Lead Regulatory Compliance — C360
C360 contains 2.5–3.7% lead. Before specifying C360, verify compliance with: RoHS (EU Directive 2011/65/EU — leaded brass may qualify under Exemption 6(c) for machining alloys); REACH (lead is an SVHC — articles containing >0.1% Pb require supply chain notification); California Proposition 65 (lead requires a Prop 65 warning for products sold in California); and the US Safe Drinking Water Act (prohibits >0.25% lead in wetted surfaces of potable water fittings — C360 is illegal for drinking water contact). Always confirm regulatory applicability with your compliance team before specifying C360 for consumer or regulated applications.
Cost Comparison
Material cost is similar between the two alloys. The machining cost difference is substantial.
~Equal
Raw Material Cost
C360 is typically 5–10% less expensive per pound than C260, primarily because it has lower copper content (61.5% vs. 70%). The difference is small compared to machining cost.
C360 saves 40–60%
Machining Cost
C360's 100% machinability vs. C260's 30% means significantly shorter cycle times for equivalent geometry. On a $25 machined part, this can be a $6–10 savings per part in machine time alone.
C260 saves
Plating Cost (if applicable)
C360 requires lead pre-treatment before plating (bright dip + copper strike), adding $1–4 per part. C260 goes directly to the plating tank without pre-treatment.
Decision Matrix and Drawing Callouts
| Application | Recommended | Why |
|---|---|---|
| High-volume turned fittings, connectors, valves | C360 | 100% machinability = typically lowest part cost and typically shortest lead time. |
| RoHS-compliant product (electronics, medical) | C260 | C360's 3% Pb fails RoHS. C260 is lead-free. |
| Electroplated parts (ENi, silver, tin) | C260 | Uniform adhesion without lead pre-treatment. |
| Deep-drawn or cold-formed parts | C260 | 23% elongation (H02) vs. 18% for C360 — superior forming ductility. |
| Structural brass in corrosive environment | C260 | Lower zinc content and no lead phases improve dezincification resistance. |
| Decorative brass with bright finish (polished) | C260 | Uniform microstructure polishes without lead phase pitting. |
| General machined fittings, non-plated, non-RoHS | C360 | Lowest cost-per-part for machined brass with no other constraints. |
Drawing Callout Format
C26000 — Cartridge Brass
Brass, UNS C26000, ASTM B36 (sheet) or ASTM B21 (rod/bar), Half-Hard (H02)For RoHS applications, add: "Lead-free brass required — C36000 not acceptable." ASTM B21 covers naval brass and general brass rod — do not use B16, which is specific to C360 free-cutting brass. For formed or drawn parts, specify the final required temper after forming, not the as-machined temper.
C36000 — Free-Cutting Brass
Brass, UNS C36000, ASTM B16, Half-HardHalf-Hard is standard rod stock. If plating follows machining, add: "Electroless nickel plating per ASTM B733, Class SC-2, 0.0010 in min thickness. Lead pre-treatment required per plating shop procedure prior to ENi application."
Frequently Asked Questions
What is the difference between brass 260 and brass 360?
Which brass is better for CNC machining — 260 or 360?
Is copper 360 RoHS compliant?
Does C360 brass corrode?
Can brass 260 and brass 360 be plated?
How do I specify brass on an engineering drawing?
What is the difference between bronze and brass?
What is brass made out of?
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