Brass 360 (C360) CNC Machining

The 100% on the scale

Every machinability rating you have ever read is expressed relative to something. In steel, the reference is a plain free-cutting steel. In copper alloys, the reference is C36000 — free-cutting brass. When a data sheet says a material machines at “60%”, it means 60% of what brass 360 does.

That is worth pausing on, because it explains the grade’s whole commercial position. Brass 360 is not merely a free-machining material. It is the benchmark that the rest of the industry is measured against, and no steel we run comes close to it.

The reason is the lead. Copper and zinc form a solid solution; lead does not dissolve in it at all. So the lead sits in the metal as a dispersion of discrete particles, and those particles do two jobs at the cutting edge:

• They break the chip. The chip fractures into short pieces instead of forming a long ribbon, because the lead particles act as stress raisers inside it.
• They lubricate the cut. Lead smears across the tool-chip interface as a solid film, cutting friction and temperature right where the work happens.

The visible result is a part that comes off the machine bright, accurate and finished, generally without a second operation. On small parts in volume, that is the difference between a competitive price and an uncompetitive one.

Where brass 360 sits against the other copper alloys

	Brass 360	Brass 260	Bronze	Copper 110
Machinability	100% — the reference	Poor — a forming grade	Varies by family	Poor — gummy
Lead	~2.5–3.7%	None	Often present in bearing grades	None
Conductivity	~28% IACS	~28% IACS	Low	~101% IACS
Best for	Turned and milled parts	Deep drawn parts	Bearings and wear	Electrical conductors

The pattern across the copper family is the same one that runs through steels: the grade that machines best is the grade with an addition you may have to declare, and the grades that are purest are the hardest to cut. Brass 360 and copper 110 sit at opposite ends of that trade. Our brass vs bronze vs copper article sets out the wider comparison.

The lead question — read this before specifying

The lead in brass 360 is the first thing to settle, and there are two separate restrictions that get confused with each other.

Electrical and electronic equipment. Lead is restricted, and the framework carries an exemption for copper alloy containing up to 4% lead by weight. Brass 360’s lead content, roughly 2.5–3.7%, falls inside that range. The exemption exists precisely so that free-cutting copper alloys remain usable — but it is an exemption, not an absence, and any declaration has to state the lead content accurately rather than describing the part as lead-free.

Potable water contact. This is the one that catches people out. Many markets restrict lead in components that contact drinking water, and the limits there are far stricter than the electronics exemption. A leaded brass fitting is generally not acceptable for wetted potable-water service, regardless of what the electronics framework allows. The two rules are not interchangeable, and an electronics exemption does not make a plumbing part acceptable.

So the honest position is:

• Brass 360 is a legitimate, widely used engineering material, and its lead content sits within the range covered by the copper-alloy exemption.
• Whether that matters depends on the application and the market, not on the material alone.
• Where a lead-free brass is required, name the designation on your drawing. We will confirm availability and quote to it rather than substituting something else and hoping.

Tell us the destination market and what the part touches at the enquiry, and the question gets settled before it becomes an expensive one.

Machining brass 360

This is the material where the usual austere advice genuinely does not apply — 360 is designed to be run hard.

• Run it fast. C360 tolerates cutting speeds that would destroy tooling in any steel. Feeding it conservatively throws away the reason for the grade.
• Chip control is trivial. Chips break short, so deep roughing passes are comfortable and there is no tangle to manage.
• The finish comes up bright without effort — often to a standard that would need a finishing operation in steel.
• Tool life is long, because the material is soft and the lead keeps friction down.
• Coolant is optional on many operations. Brass conducts heat well and the cut runs cool; on simple turning, dry machining is common. On heavier milling or deep drilling, coolant or air blast is still worth having for chip evacuation.

Two cautions worth naming.

Brass is soft, and small features deform. Very fine threads, thin walls and slender sections can be damaged by the tooling or by the clamping pressure even though they cut cleanly. Where a part has a fine thread or a thin wall, saying so at the enquiry lets the setup be planned around it.

Brass is abrasive on tooling over long runs — not because it is hard, but because brass swarf is abrasive when it gets recirculated. Keeping the machine clean and the coolant filtered pays back over a production run.

Precision features are held to ±0.01 mm with ISO 2768-m as the general tolerance block — see tolerances we hold. Brass is a good material for tight tolerances because it is dimensionally stable and cuts without distorting.

Corrosion behaviour, and the two failure modes to know

Brass 360 performs well in most indoor and mild service, and that is where most of it is used. Two specific failure modes are worth knowing because both are environment-driven rather than alloy-driven.

Dezincification. In some waters — particularly stagnant, warm or aggressive ones — the zinc is selectively leached out of the alloy, leaving a porous copper-rich residue that has neither the strength nor the corrosion resistance of the original metal. The part looks intact and fails structurally. Where a brass part sits in prolonged contact with water, the application and the water chemistry both matter, and they are worth stating at the enquiry.

Stress-corrosion cracking in ammonia. Brasses are susceptible to cracking under sustained tensile stress in the presence of ammonia and amines. This is why brass fittings are stress-relieved after cold working where they are destined for that kind of service, and why a part that will see ammonia should be flagged rather than quoted silently.

Neither of these makes brass 360 a bad material. Both are reasons to say what the part touches.

Where brass 360 is the right choice

• Fittings, valve bodies and stems in general service
• Small turned fasteners — nuts, screws, threaded inserts, nipples
• Bushings, bearings and wear parts in light-duty applications
• Gears and worm wheels running against steel
• Electrical terminals, connectors and contacts where 28% IACS is sufficient
• Instrument and gauge parts that need to be non-magnetic and dimensionally stable
• Decorative and architectural hardware, where brass is often plated or polished anyway
• Any small part produced in volume where cycle time and finish decide the price

Where brass 360 is the wrong choice

Potable water contact. The lead content rules it out in most markets that regulate wetted plumbing. Name the lead-free designation you need and we will quote to it.

Anything welded or brazed. The lead volatilises into toxic fume and the joint quality is poor. Brass assemblies should be designed around mechanical joints, or built in a lead-free grade.

High-conductivity electrical duty. At around 28% IACS, brass is roughly a quarter as conductive as pure copper. Where the current path is long or the cross-section is limited, the grade is copper 110 or copper 101.

Heavy wear or load-bearing service. Brass is a light-duty bearing material. Where a bushing carries real load, bronze is the family — the bearing bronzes exist precisely for that duty.

Deep-drawn or severely formed parts. Brass 260 is the forming grade; 360 carries lead for cutting and is not chosen for its formability.

Prolonged immersion in aggressive water, or ammonia service. Both are environments where brass 360 has specific weaknesses. Say so and the alloy, the stress relief and the design can be reviewed together.

Finishing brass 360

Brass machines to a good finish, so the finishing operation is usually about appearance, protection or contact resistance rather than about correcting the surface.

• Nickel plating — a hard, bright barrier, common on hardware and electrical parts. Nickel also acts as a diffusion barrier under gold on connector contacts
• Chrome plating — a hard, decorative finish for visible hardware, usually over a nickel layer
• Polishing and brushing — brass polishes to a deep reflective finish, and takes a directional grain well
• Tumbling and deburring — the standard route for small turned parts, and often the only finishing operation needed

One practical point: bare brass tarnishes. It darkens over time in air, and the rate depends on humidity and sulphur compounds in the atmosphere. Where a part has to stay bright, it needs a lacquer, a plating or a passivation, and that has to be specified rather than expected. Where a decorative brass finish is wanted with a protective layer, saying so at the enquiry is enough for the right route to be chosen.

All finishing runs through our vetted partner network, managed under one quality process. The grades we run across every process are listed on the materials page.

What to put on the drawing

Instead of	Write
Brass	Brass 360 (C360), if the part is turned or milled
Brass 360, potable water contact	Not acceptable — name the lead-free designation you require
Brass 360, electrical or electronic	Fine under the copper-alloy exemption — say the market so the declaration is right
Brass 360, will be welded	Not weldable — the lead gives off toxic fume
Brass 360, high-current conductor	Wrong grade at ~28% IACS — use copper 110 or 101
Brass 360, heavy-load bearing	Wrong grade — use a bearing bronze
Brass 360, will sit in water	Flag it — dezincification depends on the water and the duty
Brass 360, must stay bright	State the finish — bare brass tarnishes

The three lines that decide most brass 360 specifications are what the part touches, which market it is sold into, and whether it is cut or formed. The first two settle the lead question before it becomes a compliance problem; the third settles whether 360 or 260 is the grade at all.

Material is bought against your drawing for your job, and every batch ships with a material certificate (MTR) tracing the grade to its mill heat plus pre-shipment photos of the actual parts. Orders start at 50 pieces per style and material, samples from a single piece in 5–10 days, and production runs in 25–35 days after sample approval. Send the drawing through the request a quote form and the reply comes back within 24 hours with DFM feedback — including a note on the lead declaration and the finish where either applies.