🟡 BRASS
CNC Machining Brass: C360 Free-Machining, C260 Cartridge and Naval Brass
If aluminum is the benchmark for fast machining, free-machining brass is the gold standard. C360 sets the 100 on the machinability rating scale that every other metal is measured against, and it earns it: brass cuts at blistering speeds, breaks chips perfectly, and leaves a bright finish with almost no tool wear. The complications are not at the spindle but in the metallurgy, lead content and dezincification, that decide which brass a buyer can actually use.
ISO 9001ISO 13485
C360: the material that defines machinability 100
C360 free-machining brass is the reference point for the entire machinability rating system, defined at 100 against which steel sits around 50-70 and aluminum somewhat above. The reason is its roughly 3 percent lead content, which forms microscopic inclusions that break chips into tiny pieces and lubricate the cut. The result is extraordinary: high spindle speeds, light cutting forces, near-perfect chip control, minimal tool wear, and a bright as-machined finish that often needs no secondary work.
For screw-machine and Swiss-turned parts, C360 is the dream material. Fittings, valve bodies, fasteners, gears, instrument components and plumbing hardware are produced at high volume and low cost precisely because brass cuts so freely. Cycle times and tool consumption are the lowest of any common metal, which is why high-volume turned parts gravitated to brass for over a century.
The one caveat at the machine is that brass is soft, so thin walls deflect and burrs, though minimal, do occur. But by every measure that drives cost, speed, tool life, finish, brass is the easiest metal to machine, and that is its core value proposition for buyers chasing low piece-price on detailed turned parts.
C260, naval brass and the lead-free question
C260 cartridge brass has higher zinc and no significant lead, giving it excellent cold formability (it is the classic ammunition-case and deep-draw alloy) but noticeably worse machinability than C360, since there is no lead to break chips. You choose C260 when forming or drawing matters, not when machining dominates. Naval brass (C464) adds about 1 percent tin to fight dezincification in seawater, making it the marine grade for fittings, fasteners and hardware exposed to salt; it machines reasonably but again lacks C360's free-cutting magic.
The defining modern issue is lead. Traditional C360's lead content runs afoul of drinking-water regulations (US Safe Drinking Water Act 'lead-free' limits) and RoHS-type restrictions for some applications. For potable-water plumbing, medical, and many consumer parts, buyers must specify low-lead or lead-free brasses such as C69300 (EnviroBrass) or C87850 and similar bismuth-bearing alloys. These machine well, though typically not quite at C360's level, and cost a bit more.
The practical guidance: if the brass part touches drinking water or falls under lead restrictions, do not default to C360. Confirm the regulatory requirement and specify a compliant low-lead grade up front, because retrofitting compliance after tooling is set is expensive.
Finishing, tolerances and cost reality
Brass holds tight tolerances readily, +/-0.005 in routine and +/-0.001 in or better on Swiss-turned features, helped by its free-cutting behavior and good dimensional stability. Its low cutting forces mean less part deflection than soft aluminum or copper in many cases, and threads cut cleanly, which is why brass dominates precision fittings and instrument parts.
As-machined brass already looks good, a bright gold finish, so many parts ship unfinished. Where appearance or corrosion matters, options include polishing to a mirror, nickel or chrome plating, and clear lacquer or anti-tarnish treatment to preserve the bright color, since bare brass tarnishes over time. For electrical contacts, tin, nickel or gold plating is applied.
On cost, brass stock is more expensive per pound than steel or aluminum because of its copper and zinc content, and commodity prices move it. But the machining savings often offset the material premium for detailed, high-feature parts: a complex fitting that would be slow and tool-hungry in stainless is fast and cheap in C360. For high-volume turned parts, brass frequently delivers the lowest total piece price despite costing more per pound of raw material.
Frequently Asked Questions
Free-machining brass C360 is literally the benchmark that defines the machinability rating scale at 100, with steel around 50-70 and most other metals rated relative to it. Its roughly 3 percent lead content forms tiny inclusions that break chips into small pieces and lubricate the cut, producing a combination no other common metal matches: very high spindle speeds, light cutting forces, excellent chip control with no stringy chips, minimal tool wear so inserts last a long time, and a bright finish straight off the tool that often needs no secondary operation. For screw-machine, Swiss-turned and high-volume detailed parts like fittings, valves, fasteners and instrument components, this translates to the shortest cycle times and lowest tooling cost of any metal. The main limits are that brass is soft, so thin walls can deflect, and that lead content creates regulatory issues for potable-water and restricted applications. But purely on machining ease, speed, tool life and finish, brass is unmatched, which is why it has been the go-to for precision turned parts for over a century.
Traditional free-machining C360 contains about 3 percent lead, which makes it non-compliant with modern potable-water regulations such as the US Safe Drinking Water Act 'lead-free' definition and various RoHS-type restrictions. For any part contacting drinking water, or for medical and consumer applications under lead limits, you must specify a low-lead or lead-free brass rather than defaulting to C360. Common compliant grades include C69300 (often sold as EnviroBrass), C87850 and other bismuth-bearing or selenium-bearing alloys that replace lead's chip-breaking role with alternative inclusions. These machine well, though usually not quite at C360's free-cutting level, and cost somewhat more. The critical buyer action is to confirm the regulatory requirement before tooling and quoting, because switching alloys after a process is set up is expensive and can require requalification. If your brass part is a plumbing fitting, faucet component, water valve, or anything contacting potable water or food, treat lead-free specification as mandatory and call it out explicitly on the drawing along with the applicable standard, such as NSF/ANSI 61 or the relevant lead-content limit.
Choose based on what the part must do beyond being machined. C360 is the right default when machining dominates, because nothing cuts faster or cleaner. C260 cartridge brass has higher zinc and essentially no lead, which gives it excellent cold formability and deep-draw behavior (it is the classic ammunition-case alloy) but noticeably poorer machinability since there is no lead to break chips. Pick C260 when the part is formed, drawn or bent rather than heavily machined. Naval brass, C464, adds about 1 percent tin specifically to resist dezincification, the selective leaching of zinc that destroys ordinary brass in seawater, so it is the marine grade for fittings, fasteners, valve components and hardware exposed to salt water. It machines acceptably but lacks C360's free-cutting speed. So the decision tree is: heavy machining and no special environment, use C360 (or a lead-free equivalent if regulated); significant forming or drawing, use C260; saltwater or dezincification-prone service, use naval brass. Matching the alloy to the dominant requirement avoids both performance failures and unnecessary machining cost.
Many brass parts ship as-machined because the bright gold as-cut surface already looks good and brass resists corrosion reasonably well in normal environments. Whether you need a finish depends on appearance and service conditions. Bare brass tarnishes over time, dulling and darkening, so if a consistent bright appearance must be maintained, a clear lacquer or anti-tarnish treatment is applied. For a mirror look, brass polishes beautifully. Where corrosion protection or a different appearance is wanted, nickel or chrome plating is common, giving a durable bright-silver or chrome finish over the brass. For electrical contacts and connectors, tin, nickel or gold plating is specified to control contact resistance and solderability. Marine parts may use naval brass plus appropriate treatment. Plating and lacquering are batched outside processes adding typically a few days to lead time, so factor them into schedule and call out masked areas. For many fittings, fasteners and industrial components, though, the practical answer is that as-machined brass is perfectly serviceable and shipping unfinished saves both cost and time.
Per pound of raw material, yes, brass costs more than aluminum or carbon steel because it is a copper-zinc alloy and copper is a relatively expensive, commodity-priced metal, so quotes on larger or heavier parts move with metal markets. But raw material price is only part of the total part cost, and brass's extraordinary machinability often flips the comparison on detailed, high-feature parts. Because C360 cuts at very high speeds with minimal tool wear and excellent chip control, cycle times and tooling costs are the lowest of any metal, so a complex turned fitting that would be slow and tool-hungry in stainless can be fast and cheap in brass. For high-volume Swiss-turned and screw-machine parts with many features, brass frequently yields the lowest total piece price despite the higher material cost, which is exactly why the precision turned-parts industry standardized on it. The honest rule: for simple, low-feature parts, aluminum or steel may be cheaper overall; for detailed, high-volume turned parts where machining time dominates, brass often wins on delivered cost even though the stock is pricier.
Last updated: July 2026
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