Brass CNC Processing Service for Precision Turned and Milled Parts

The copper-zinc family covers a wide range of compositions, and the difference between them shows up on the shop floor within the first few parts. C36000, the free-cutting grade, machines faster than anything else in the family. It runs at high surface speeds, breaks chips cleanly, and leaves a decent finish straight off the tool. The trade-off is lead content, roughly 3 percent, which rules it out for potable water contact and for some medical and food-path parts.

C27400 and C28000 carry no deliberate lead addition and hold up better under stress. They are the grades to pick when the part will be soldered, brazed, or formed after machining, or when the application calls for higher tensile strength. Both cut reasonably well, though you should expect shorter tool life and more attention to chip evacuation than with C36000.

C110 and C101 are technically coppers rather than brasses, but they show up in the same conversations because they machine on the same equipment. Conductivity drives the choice here. Bus bars, RF shields, and electrical contacts usually land on C110. If the part needs to carry current and also take a thread, that is worth flagging early, because the soft grades deform under clamping pressure more than a free-cutting brass will.

Beryllium copper is the outlier. It machines to high strength and keeps good conductivity after heat treatment, which is why it appears in springs, connectors, and non-sparking tooling. Beryllium dust is a health hazard, so the shop needs dust control and the drawing needs to say so. We run it, but we quote it separately and schedule it away from open machining cells.

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  C36000Fastest to cut, best surface finish, contains lead.
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  C27400 / C28000Lead-free, good for brazing and higher load.
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  C110 / C101High conductivity, soft, easy to mark when clamped.
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  Beryllium copperHigh strength plus conductivity, needs dust control.

Most copper-zinc work is turned, not milled. Fittings, bushings, valve bodies, and connector shells are all bodies of revolution, and a lathe with a bar feeder produces them faster and cheaper than any other route. We run these on mill-turn centers so a cross-drilled hole or milled flat comes off the same setup. That matters on parts with true position callouts, because one setup removes the stack-up you get from moving the part between machines.

Milled features are common on housings, manifolds, and instrument frames. The metal cuts freely, so cycle times are short and tool wear is low compared with stainless or titanium. The problems that do appear are usually thermal or mechanical rather than metallurgical. Thin walls deflect under cutting force. Long slender parts bow. Both are manageable with light passes, sharp tooling, and support, but the drawing has to allow for it.

On tolerance, ±0.005 mm is achievable on critical diameters and bores when the feature is short, rigid, and measured on the machine or in a temperature-controlled room. It is not a blanket number for every dimension on the print. A 300 mm long shaft held at both ends will move more than that during the cut. As-machined finish sits around Ra 1.6–3.2 μm; fine turning and burnishing reach Ra 0.8–1.6 μm, and lapping pushes into Ra 0.2–0.8 μm when the geometry allows.

Wall thickness is the other number worth checking before you send a file. Below roughly 0.5 mm on a free-cutting grade, chatter and distortion start to dominate, and you are better off redesigning the feature or switching material than asking the shop to hold a spec the geometry will not support.

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  One setup winsCross holes and flats on the same machine avoid stack-up.
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  Thin wallsUnder 0.5 mm, expect chatter and rework.
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  Long partsSupport them or split the tolerance across the print.

Copper-zinc parts take plating and coating well, and the finish is often what the customer sees first. Electroless nickel gives a hard, uniform layer that resists tarnish and holds up in wear contact. Silver and gold plating are standard for electrical contacts where contact resistance matters. Zinc plating is the economical choice for general corrosion protection on hardware.

Mechanical finishes are just as common. Bead blasting produces a matte, uniform surface that hides tool marks. Tumbling and brushing soften edges and remove burrs from high-volume runs. Polishing gets you to a reflective surface for decorative hardware. If the part carries laser marking, note that the minimum character height we can hold is 1.5 mm, and contrast is better on a blasted or plated surface than on a mirror polish.

Inspection follows the drawing, not a default script. We check incoming stock, monitor dimensions during the run, and inspect 100 percent of parts before shipment on features the print calls out. Reports are available on request. For plated parts, the plating thickness and adhesion check happen at the coater and the certificate travels with the lot.

One practical note on leaded grades. If your part will be plated and the application is sensitive to lead leaching, tell us at quoting. Switching from C36000 to a lead-free grade after the first article is a re-quote, not a tweak.

Copper-zinc is the right answer when the part needs good electrical or thermal conductivity, easy machining, corrosion resistance in mild environments, and a clean cosmetic surface. Instrument fittings, valve bodies, connector shells, RF housings, and decorative hardware all fit that profile. Prototype quantities and full production runs both make sense, and there is no minimum order quantity here, so a single piece is as welcome as a 10,000-part release.

It is the wrong answer in a few situations. Parts exposed to ammonia or amine compounds will stress-crack, and the failure is sudden rather than gradual. Seawater service calls for a different alloy family; copper-zinc alloys dezincify in salt water unless the grade is specifically stabilized for marine use. High-temperature service above roughly 200 °C is also a poor fit, because strength drops and creep becomes a design concern.

Leaded grades are another boundary. C36000 machines beautifully, but it is not acceptable for potable water contact in many jurisdictions, and some medical and food-path applications rule it out. If the part touches drinking water or a patient, start with a lead-free grade and accept the slower cutting.

Weight is the last consideration. Copper-zinc is denser than aluminum, roughly three times heavier for the same volume. On a handheld device or a drone frame, that difference usually pushes the design toward aluminum regardless of how well the part would machine.

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  Good fitFittings, connectors, RF housings, cosmetic hardware.
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  AvoidAmmonia exposure, seawater, service above 200 °C.
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  Lead-free firstPotable water, medical, and food-path parts.