Free-cutting brass (CuZn39Pb3)
Also called: CW614N, C38500, CZ121, IS 319, leaded brass, brass rod
Free-cutting brass (CuZn39Pb3) is a copper-zinc alloy with about 3% lead, which makes it the easiest metal to machine. It is used for large numbers of turned parts such as fittings, valve parts, inserts and electrical terminals.
Quick facts
- Type
- Leaded alpha-beta brass
- Composition
- About 58% copper, 3% lead, rest zinc
- Machinability
- Excellent: the reference grade (100%)
- Tensile strength
- About 360–500 MPa depending on temper
- Density
- About 8.4–8.5 g/cm³
- Corrosion
- Good in air and water; see dezincification
Equivalent grades
| Standard | Closest grade |
|---|---|
| EN 12164 | CuZn39Pb3 (CW614N) |
| UNS / ASTM | C38500 |
| BS (old) | CZ121 |
| IS 319 (India) | Free-cutting brass rods |
Free-cutting brass or forging brass?
| Free-cutting (CuZn39Pb3) | Forging (CuZn40Pb2) | |
|---|---|---|
| Designation | CW614N, CZ121 | CW617N, CZ122 |
| Best for | Machining from bar | Hot forging, then machining |
| Lead | About 2.5–3.5% | About 1.6–2.5% |
Points to know
- In hot water and some waters, ordinary brass can lose zinc (dezincification): use DZR brass for plumbing fittings
- For drinking water, regulations in many countries limit lead: ask for lead-free or low-lead brass where needed
- It can be plated with nickel or chrome, or used bare
Typical uses
- Plumbing and gas fittings
- Valve bodies and stems
- Electrical terminals, pins and inserts
- Threaded inserts for plastics
- Precision turned parts made in large numbers
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Questions
- Why is CuZn39Pb3 called free-cutting brass?
- Its lead breaks chips into small pieces and lubricates the cut, so it machines faster and cleaner than any other common metal.
- What is the difference between CZ121 and CZ122?
- CZ121 (CuZn39Pb3) is made for machining from bar; CZ122 (CuZn40Pb2) is made for hot forging.
- Is brass safe for drinking water parts?
- Ordinary leaded brass may not meet drinking-water rules on lead. Use a lead-free or certified low-lead, dezincification-resistant brass for those parts.
The figures on this page are typical values for guidance, written by Diemeco from standard engineering practice. They are not a specification: confirm grades and properties with the relevant standard or the supplier's mill test certificate, and tolerances with your workshop. Last checked 8 October 2026.