Guides / Materials
Which Brass Alloy to Specify for a Machined Part
September 21, 2026
Most machined brass parts are made from one alloy: C360. It is the benchmark, it is the cheapest to cut and it is held in stock everywhere. The useful question is not which brass is best, but what would push you off C360.
There are four things that do it: lead limits, corrosion, the starting shape and strength.
C360 free-cutting brass, the default
CuZn36Pb3 in European terms, CW603N. About 61.5 percent copper, 35.5 percent zinc, 3 percent lead. Machinability 100 by definition.
If the part is turned from bar, is not wetted by drinking water and does not live in seawater, this is the answer. Short chips, clean threads, a bright surface straight off the tool and tolerances of ±0.01 mm routinely held on turned features.
C385 architectural bronze, for profiles and visible parts
CuZn39Pb3, CW614N. More zinc, slightly less copper, still around 3 percent lead. Rated near 90.
Despite the name it is a brass, not a bronze. It is supplied mainly as extruded shapes rather than round bar, so it is the usual starting point for hinges, handles, trim, window and door hardware, and anything that begins life as a profile. It polishes brightly, which is why it dominates where the part is seen.
C377 forging brass, for high volume chunky parts
CuZn39Pb2, CW612N. Rated near 80.
The point of C377 is not machining, it is what happens before machining. The part is hot forged to a near net shape, then machined only where a sealing face or a thread requires it. Above roughly 5,000 pieces of a bulky fitting, the material saved usually pays for the forging die several times over. Below that, turning from bar is cheaper.
Ask about it when your part is heavy relative to its finished size and the annual volume is real.
C464 naval brass, for seawater and hot water
CuZn39Sn1. About 1 percent tin, which suppresses dezincification, the failure mode where zinc leaches out of brass and leaves a porous copper sponge behind. Rated 30.
That rating is the cost. Naval brass produces long chips and slow cycles, so it should be specified because the environment demands it, not because it sounds like a stronger material. Marine hardware, heat exchanger parts and hot water fittings are the usual homes. In Europe the same problem is often solved with a DZR grade such as CW602N instead.
C260 cartridge brass, rarely the right answer for machining
70 percent copper, 30 percent zinc, no deliberate lead. Rated 30.
C260 exists for deep drawing and cold forming. It is ductile, it work hardens and it produces long stringy chips when cut. When it turns up on a machining drawing it is usually inherited from a stamped design that changed process without changing material. Ask whether C360 would do, because it usually would.
The lead-free grades
Covered in full in leaded and lead-free brass compared. Short version: silicon brass in the C69300 family is the usual answer for potable water, roughly twice as strong as C360 and dezincification resistant, rated near 80. Bismuth brasses in the C49300 family are the closer drop-in replacement for an existing C360 program, also near 80, with thinner stock availability.
Side by side
| Grade | Lead, nominal % | Machinability | Picked because |
|---|---|---|---|
| C360 free-cutting | 2.5 to 3.7 | 100 | Default for turned bar parts |
| C385 architectural | 2.5 to 3.5 | 90 | Extruded profiles and visible parts |
| C377 forging | 1.5 to 2.5 | 80 | High volume near net shapes |
| C69300 silicon | under 0.09 | 80 | Potable water, strength, dezincification |
| Bismuth brass | under 0.25 | 80 | Lead-free drop-in for a C360 program |
| C464 naval | under 0.20 | 30 | Seawater and hot water |
| C260 cartridge | trace | 30 | Deep drawing, not machining |
Published typical values for the alloy. They describe the material, not a promise from any shop.
How to decide in one pass
- Is the part wetted by drinking water, food or a medical fluid? If yes, go lead-free and stop here.
- Does it see seawater, hot water or ammonia? If yes, naval brass or a DZR grade.
- Does it start as an extruded profile, or does the finish have to look good? C385.
- Is it bulky and made in real volume? Ask about C377 and forging.
- Otherwise, C360.
Then write the reason on the drawing next to the alloy. A shop that knows why the grade was chosen can offer a cheaper one that still meets it. A shop that only sees a name cannot.
Frequently asked questions
What is the difference between C360 and C385?
C360 is free-cutting bar stock at roughly 61.5 percent copper, machinability 100. C385 is architectural bronze, closer to 57 percent copper with more zinc, supplied mainly as extruded shapes and rated near 90. C360 is the default for turned parts from bar. C385 is the default where the part starts as a profile or where a bright polished surface matters.
When do I need naval brass instead of ordinary brass?
When the part sees seawater, hot water above roughly 60 degrees Celsius, or another environment that strips zinc out of ordinary yellow brass. C464 adds about 1 percent tin for that reason. It is rated 30 for machinability, so it costs more to cut. Specify it for the environment, never because it sounds stronger.
Can I machine C260 cartridge brass?
You can, but it was designed for deep drawing and cold forming, not for cutting. It is rated 30 and produces long stringy chips. If a machined part arrives specified on C260 it is usually a leftover from a stamped or drawn design, and switching to C360 often cuts the price without changing anything that matters.
Is brass or bronze better for a machined part?
They answer different questions. Brass is copper and zinc, cheaper and far easier to machine. Bronze is copper and tin or aluminum, better in bearings and under load in seawater. For fittings, valves and connectors brass is almost always the right family, and the choice is which brass.
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