Brass — the most machinable common metal
Brass is a copper-zinc alloy family with a machinability rating (using C360 as the baseline of 100%) higher than any other common engineering metal. For comparison: 6061 aluminum is rated 90%, 12L14 free-machining steel 85%, 304 stainless 45%, 316 stainless 35%. This isn't a small difference: a part that takes 10 minutes in 316 often takes 2 minutes in C360. For high-volume production of small fittings and connectors, that cycle-time difference is the economic reason brass dominates plumbing, valve, and electrical connector manufacturing worldwide.
Our typical brass customer is building plumbing fittings (valve bodies, compression fittings, ferrules), electrical connectors (pin terminals, RF connector bodies, grounding hardware), musical instrument components, marine hardware, or decorative architectural hardware. Order sizes range from 10-piece prototypes to 10,000+ piece production runs, with bar-fed Swiss turn for anything rotationally symmetric.
Choosing the right brass alloy
The alloy choice drives both machinability and downstream behavior. Our defaults:
- C360 / UNS C36000 (free-cutting brass, 61.5% Cu / 35.5% Zn / 3% Pb): the baseline machinability champion. Use for 90% of machined brass parts where lead content is acceptable (non-drinking-water applications). JIS equivalent: C3604.
- C385 (architectural bronze, 57% Cu / 40% Zn / 3% Pb): readily extrudable into complex profiles; we machine from extruded stock when the base profile nearly matches finished geometry.
- C260 (cartridge brass, 70/30): excellent cold-form capability. Used for deep-drawn parts that need downstream machining. Lower machinability (75% of C360) but better ductility.
- C464 (naval brass, 60% Cu / 39.2% Zn / 0.8% Sn): tin addition improves saltwater corrosion resistance. Default for marine hardware and offshore fittings.
- C693 / C6932 / EnviroBrass: lead-free alternatives meeting NSF/ANSI 61 and California AB 1953 / Vermont Act 193 for drinking-water applications. Cost ~25% more, ~70% the machinability of C360.
When in doubt between C360 and lead-free: ask where the part ends up. If it contacts drinking water anywhere downstream, specify lead-free. If it's an industrial fitting, electrical connector, decorative hardware, or musical instrument, C360 is correct and cheaper.
Machining parameters — fast, clean, tool-friendly
C360 machines easier than almost anything. Our roughing parameters: 180–250 m/min surface speed, 0.10–0.20 mm feed per tooth, 2–5 mm axial depth of cut. Finishing 250–350 m/min with sharp-edge carbide. Uncoated carbide is fine — coated tooling doesn't extend life meaningfully on brass because the lead particles clean the cutting edge continuously. For high-volume production Swiss we've run HSS tooling for tens of thousands of parts without tool changes. Mist coolant or minimal flood — brass chips don't weld to the tool and don't need heavy cooling. Chip management is easy because lead breaks chips short.
Lead-free brass (C693, C6932) runs at roughly 70% of C360 speeds. C260 and C385 run at 80–85%. Naval brass (C464) runs at 75% and needs slightly more generous tooling radius to prevent edge chipping from the tin content. For detailed Swiss-turn parameter development on high-volume jobs we hold sample parts aside during first-piece setup to dial in surface speed and feed — small adjustments produce large cycle-time gains on 5,000+ piece runs.
Finishes — bright dip, plating, PVD, and lacquer
Brass oxidizes over time, developing the classic brown patina that some customers love and others reject. Finish options we provide:
- Bright dip: acid dip + passivate for shiny gold finish. Standard starting point for decorative brass. Adds ~2 hours, cost ~3% of finished-part price.
- Nickel plate: silvery, corrosion-resistant, standard for electrical connectors and hardware. Typical 5–10 µm bright nickel or 15–25 µm electroless nickel for wear applications. +3 days lead time.
- Chrome plate: classic plumbing fixture finish — bright chrome over nickel underlayment. +5 days.
- PVD coating: gold, rose gold, brushed gold, black, gunmetal, satin bronze — durable decorative finish popular for high-end architectural hardware and watches. +7–10 days, premium cost.
- Polish + lacquer: hand-polished high gloss sealed with clear acrylic lacquer. Prevents tarnishing indefinitely. Standard for musical instruments and premium decorative work.
- Brushed / satin: directional grain for architectural hardware, often combined with lacquer.
Swiss turn vs mill — picking the right machine
For rotationally symmetric brass parts (ferrules, connector bodies, valve stems, fittings up to 42 mm diameter), Swiss turn is almost always correct. Our Swiss machines run bar stock with live tooling and back-working, completing full complex geometry in one operation — no second-op setup, no transfer losses. Typical cycle time for a 25 mm diameter brass fitting: 25–45 seconds per part.
For prismatic brass parts — valve bodies with multiple port orientations, complex decorative hardware, larger architectural fittings — 4-axis or 5-axis mill is correct. We route decisions based on geometry, not preference: if Swiss can do it in one op, Swiss wins on cost. If the part needs features on 3+ non-coaxial faces, mill wins.
What to send for a brass quote
Required: STEP file, PDF drawing with tolerances, alloy callout (C360 is our default unless otherwise specified; confirm if NSF lead-free required), finish specification, target quantity, target delivery. Helpful: application context (helps us suggest alloy or DFM improvements), plating specification with thickness, packaging requirements (individually bagged vs bulk). For high-volume repeat production, we keep bar stock on-hand in common sizes for same-week restart on repeat orders. See the quality process page for inspection and documentation scope.