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Ask any machinist which metal they would rather cut all day, and the answer is almost always the same: C360 brass. Known as free-machining brass or free-cutting brass, C360 carries a machinability rating of 100% — the baseline against which every other metal is measured. But what exactly makes this copper-zinc alloy the default choice for brass CNC machining, and when should you consider a different grade? This guide breaks down the metallurgy, the economics, and the practical considerations behind C360.
C360 (UNS C36000) is a leaded brass alloy made primarily of copper and zinc, with a small but critical addition of lead. Its typical chemical composition is:
That 2.5–3.7% of lead is the whole story. Lead does not dissolve into the copper-zinc matrix; instead, it disperses throughout the alloy as microscopic particles. During cutting, these particles act as built-in chip breakers and an internal lubricant, which is why C360 behaves so differently from other brass grades at the spindle.
| Property | Typical Value |
|---|---|
| Machinability rating | 100% (industry baseline) |
| Tensile strength | 340–470 MPa |
| Yield strength | 140–310 MPa |
| Elongation | 15–53% |
| Hardness | 78–90 HRB |
| Density | 8.49 g/cm³ |
| Electrical conductivity | ~26% IACS |
| Melting range | 885–900 °C |
The dispersed lead particles fracture the chip as it forms, producing small, broken chips that evacuate easily from the cutting zone. Compare that with C260 cartridge brass or stainless steel, which generate long, stringy chips that wrap around tools, scratch finished surfaces, and force operators to stop the machine to clear them. Short chips mean unattended, lights-out running is genuinely practical.
C360 can typically be turned and milled at cutting speeds three to five times higher than stainless steel, with tool life five to ten times longer than when cutting steel. Because the alloy generates low cutting forces and does not work-harden, lighter setups and smaller tooling are possible. On high-volume turned parts, the cycle-time reduction alone frequently cuts per-part cost by 30–50% compared with a stainless steel equivalent — often enough to offset brass's higher raw material price entirely.
Free-machining brass comes off the lathe with a smooth, bright finish — Ra 0.8 µm is achievable straight from the tool without secondary grinding or polishing. For fittings, connectors, and decorative hardware, that means fewer finishing operations and faster delivery.
Because cutting forces are low and the material is dimensionally stable under the tool, C360 holds tight tolerances reliably. Standard ±0.02 mm on turned diameters is routine, and precision work can reach ±0.005 mm or tighter with the right equipment. At ANOK, our CNC turning department holds tolerances down to ±0.002 mm, which makes even the most demanding brass connector and guide-pin geometries repeatable across long production runs.
Beyond machinability, C360 offers respectable corrosion resistance in plumbing, pneumatic, and general industrial environments, plus roughly 26% IACS electrical conductivity — one reason it is the standard material for terminals, connectors, and RF components.
| Alloy | Machinability | Lead Content | Best For |
|---|---|---|---|
| C360 (free-machining brass) | 100% | 2.5–3.7% | High-volume turned and milled parts |
| C260 (cartridge brass) | ~30% | ≤0.07% | Stamped, drawn, and cold-formed parts |
| C464 (naval brass) | ~30% | ≤0.20% | Marine hardware, corrosion-critical parts |
| C230 (red brass) | ~30% | ≤0.05% | Plumbing lines in corrosive environments |
The pattern is clear: if the part will be cut rather than formed, C360 wins on speed, tool life, and total cost. Grades like C260 — which we also machine regularly — make more sense when the part requires significant cold forming, or when lead content is restricted.
C360's combination of machinability, conductivity, and corrosion resistance makes it the workhorse alloy across several industries:
No material is universal, and an honest assessment matters when you select an alloy:
C360 accepts a wide range of finishes: as-machined bright finishes, mirror polishing for decorative hardware, nickel or chrome plating for corrosion and wear resistance, tin plating for solderability, and clear lacquering to prevent tarnishing while preserving the natural brass color. Having these treatments available under one roof shortens lead time and keeps accountability for the final finish with a single supplier.
A few practical steps will squeeze the full cost advantage out of free-machining brass:
As an ISO 9001:2015 certified factory, ANOK machines C260 and C360 brass daily across CNC milling, 4-axis and 5-axis machining centers, and nearly 15 CNC turning machines running 20 hours a day — handling part diameters up to 520 mm and lengths up to 3600 mm. Our in-house coating and surface treatment line covers plating, passivation, and polishing, so brass parts ship finished and ready for assembly. If you are sourcing precision brass CNC machining services for fittings, connectors, or high-volume turned components, send us your drawing for a fast, detailed quotation.
C360 earns its "preferred grade" status through simple metallurgy: roughly 3% lead that breaks chips, lubricates the cut, and lets machines run faster and longer. The result is shorter cycle times, longer tool life, excellent as-machined finishes, and reliable tight tolerances — a combination that no other common brass grade matches for cut-to-shape parts. Where lead content, welding, or high-temperature service rules it out, alternatives like C260 or C464 step in. But for the vast majority of machined brass components, C360 remains the benchmark — and the most economical path from drawing to finished part.