What Is C36000 Copper?
C36000, commonly called 360 brass or free-cutting brass, is a leaded copper-zinc alloy in which lead is added specifically to improve machinability. It is the reference material for machinability in the copper industry, rated at 100 on the machinability scale, meaning almost every other copper alloy is compared against it. Because the lead particles act as an internal chip breaker and lubricant, C36000 machines quickly, produces clean chips, and gives excellent tool life, which makes it the default choice for high-volume precision components.
Chemical Composition
Per ASTM B16/B16M, the specified composition of C36000 is: copper 60.0%–63.0%, lead 2.5%–3.7%, iron 0.35% maximum, with the balance zinc. Trace elements such as nickel and tin are normally kept at low levels to avoid hard spots that could damage cutting tools or degrade machined surface quality.
| Element | Specified Range (%) | Role |
|---|---|---|
| Copper | 60.0–63.0 | Base element; strength and conductivity |
| Lead | 2.5–3.7 | Free-cutting additive; chip breaking and lubrication |
| Iron | 0.35 max | Controlled to avoid hard spots |
| Zinc | Balance | Matrix element; strength and cost |
Hardness and Temper States
The hardness of C36000 depends on its temper. In the annealed (soft) state, typical hardness is 60–80 HB (50–65 HRB, 65–90 HV), with excellent ductility for bending and drawing. Cold work raises the hardness: the half-hard state runs about 90–110 HB (70–80 HRB), and the full-hard state about 110–130 HB (80–90 HRB), at the cost of ductility. For parts that must resist wear or hold tight tolerances, a cold-worked temper is commonly specified.
Typical Applications and Standards
C36000 is the standard material for screw-machine products: fittings, fasteners, gears, valve stems, plumbing components, terminals, and electrical connectors, as well as precision instrument parts. It is covered by ASTM B16/B16M for rod, bar, and shapes for screw machine work and by ASTM B124/B124M for forging rod, bar, and shapes. Because the alloy works so easily, it allows high spindle speeds, long tool life, and excellent surface finish in automated machining lines.
Compliance and Selection Notes
Because C36000 contains 2.5%–3.7% lead, it is not suitable for potable water contact in many jurisdictions and is restricted or exempted under regulations such as the EU RoHS Directive and local plumbing laws. Where lead content is unacceptable, lead-free machinable brasses such as C69300 or bismuth-bearing grades should be considered, accepting some reduction in machinability. When selecting C36000, verify the required temper, tolerance class, and any surface finish requirements against the applicable ASTM specification.
FAQ
What is C36000 brass?
C36000, or 360 brass, is a free-cutting leaded brass with 60%–63% copper, 2.5%–3.7% lead, and the balance zinc, rated 100 on the machinability scale.
Why is lead added to C36000?
Lead particles act as a chip breaker and lubricant, which speeds machining, improves surface finish, and extends tool life.
What is C36000 used for?
It is used for precision screw-machine parts such as fittings, fasteners, gears, valve components, plumbing fixtures, and electrical connectors.
Which standards cover C36000?
ASTM B16/B16M covers rod, bar, and shapes for screw machine work, and ASTM B124/B124M covers forging stock.
Is C36000 allowed for drinking water applications?
Generally no. Its lead content makes it unsuitable for potable water contact under most plumbing regulations; lead-free alternatives such as C69300 should be used.
How hard is C36000 brass?
Typical hardness ranges from 60–80 HB annealed to 110–130 HB in the full-hard condition, depending on temper.
