CNC Machined Brass Parts

Which brass alloy should the part be?

C360, also written C36000, is free-cutting brass: about 61.5% copper, 35.5% zinc and 3% lead (source 2). Lead is added to brass to make it machine more easily (source 1), and C360’s machinability rating of 100 is the benchmark other copper alloys are rated against (source 2). ASTM B16 is the specification for C36000 rod, bar, wire and shapes made for screw machines (source 4), so C360 is a bar-stock alloy: round parts are CNC turned from it, and small screw-machine parts are quoted under Swiss screw machining. It comes as round, square, hex and flat bar (source 3), so a fitting can start from hex bar.

Not every brass cuts like C360, and the table compares it with three brasses a print may name instead. C260 is a cold-forming brass (sources 1 and 6) that machines far less freely than C360, so question it on a part that is machined rather than formed. C69300 is a silicon brass with no lead added (source 8). Other alloys and plastics quoted on request. Name the grade on the print.

What are brass parts good for?

Brass and bronze are often chosen for bearings, bushings and other sliding parts because they resist galling (source 9); sleeve bearings and other bushings are covered on custom bushings. Brass is also used where corrosion resistance and low friction are both needed, in valves, hose couplings and electrical plugs and sockets, and as a non-sparking metal for fittings and tools used near flammable or explosive materials (source 1). A threaded adapter or hose barb in brass is quoted like any custom fitting, and a brass shaft or pin like the parts on shafts and pins.

For electrical hardware, C360 conducts at 26% IACS (source 3), about a quarter of the standard value for commercial copper (source 10), and C260 is a little higher at 28% (source 6). Brass terminals, contacts and connector bodies give up that conductivity for C360’s machinability. Decorative and instrument parts use brass for the look of the metal: turned and knurled custom knobs and billet bezels are both quoted in it. A brass thumb screw or an odd thread comes under custom fasteners.

Two limits are worth weighing before you pick it. Brass runs 8.4-8.73 g/cm³ (source 1) against 2.70 g/cm³ for 6061 aluminum (source 11), so the same part weighs a little over three times as much in brass; when conductivity, friction and looks don’t matter, 6061 is the lighter choice. And C360 is joined by soldering or brazing, not arc welding (sources 2 and 3), which matters if the part is meant to go into a weldment.

How does brass hold up in service?

In the presence of oxygen and moisture, brass with more than 15% zinc can lose zinc, the selective leaching called dezincification. Chlorine-containing water is one setting where it occurs, and stagnant or slow-moving water makes it worse (source 12). Dezincification-resistant (DZR) brasses are used where that risk is large (source 1).

Brass is also prone to stress corrosion cracking from ammonia or anything that gives it off, the failure known as season cracking (source 1). C69300’s mill lists it as resistant to both dezincification and stress corrosion cracking (source 8), so it is one to consider where either is a risk.

Parts come back finished and inspected. If a surface has to stay bare, mark it on the print; the surface finishes page covers how to call a finish out.

What should the print say for a brass part?

Name the alloy and temper together, such as C36000 per ASTM B16, H02 (half hard), rather than just brass. For reference, typical H02 values up to 1 in diameter are 58 ksi tensile and 45 ksi yield (source 5). No C of C or material certifications ship with parts by default. If your PO needs them, say so before the quote. Inspection reports on critical dimensions aren’t included by default. If you need one, ask when you place the order.

Mark the critical dimensions with their tolerances. A STEP file with no drawing is quoted to a ±0.005 in general tolerance, or the one your notes name; what file to send covers that rule. A fit between brass and steel changes with temperature, because brass grows about 19 millionths of its length per °C against 11-13 for steel (source 13), so give the operating temperature when an assembly runs hot or cold.

Ask for more than one quantity, such as 1, 25 and 100, and the quote shows each. Rush 1-2 weeks applies to machined parts with no secondary operations. Heat treat, grinding, EDM and finishing add time, and the quote gives the real date. Lead time starts at order approval. Put your need date in the part description and the quote answers it.

Sources

All accessed 27 September 2026. Where a figure here differs from your print, the print governs.

1. Wikipedia, “Brass”: en.wikipedia.org (copper and zinc, bronze with tin instead; lead added for machinability; low-friction and corrosion-resistant uses; non-sparking fittings and tools; DZR brasses; stress corrosion cracking from ammonia, season cracking; density 8.4-8.73 g/cm³; copper sulfide tarnish and green-blue patina).

2. AZoM, “Free Cutting Brass UNS C36000”, 12 November 2012: azom.com/article.aspx?ArticleID=6391 (61.5% copper, 3% lead, 35.5% zinc; machinability with C36000 = 100 as the reference; brazing and soldering suitable, arc welding methods not recommended).

3. Farmers Copper, “C36000 Free-Machining Brass”: farmerscopper.com/free-machining-brass-c36000.html (composition per ASTM B16; 26% IACS; not recommended for welding; round rod, square, hex and rectangle bar).

4. Farmers Copper, “ASTM B16 Standards”: farmerscopper.com/astm-b16.html (ASTM B16, Standard Specification for Free-Cutting Brass Rod, Bar and Shapes for Use in Screw Machines, covering C36000 rod, bar, wire and shapes).

5. Sequoia Brass & Copper, “C36000 Brass”: sequoia-brass-copper.com/brass-supplier/360-brass/ (typical 58,000 psi tensile and 45,000 psi yield up to 1 in diameter in H02, half-hard, temper).

6. Farmers Copper, “260 Brass, C26000 Cartridge Brass”: farmerscopper.com/cartridge-brass-260-c260-c26000.html (machinability 30; 68.5-71.5% copper, 0.07% lead max; 28% IACS; excellent cold forming; plate, sheet, strip, bus bar and round bar).

7. Farmers Copper, “C46400 Naval Brass”: farmerscopper.com/naval-brass-464-c464-c46400.html (machinability 30; nominal 0.7% tin, 0.20% lead max; resistance to seawater, for salt and fresh water immersion).

8. Wieland Chase, “ECO BRASS Lead Free Alloys”: wieland-chase.com/eco-brass/ (C69300 silicon brass, no lead added; dezincification and stress corrosion cracking resistant; excellent machinability; valves and fittings).

9. Wikipedia, “Galling”: en.wikipedia.org (brass and bronze chosen for bearings, bushings and sliding applications for their resistance to galling).

10. Wikipedia, “International Annealed Copper Standard”: en.wikipedia.org (IACS as the standard value for the conductivity of commercially available copper).

11. Wikipedia, “6061 aluminium alloy”: en.wikipedia.org (density 2.70 g/cm³).

12. Wikipedia, “Selective leaching”, section “Leaching of zinc”: en.wikipedia.org (dezincification of brass over 15% zinc with oxygen and moisture; chlorine-containing water; stagnant or low-velocity water).

13. Wikipedia, “Thermal expansion”: en.wikipedia.org (linear coefficients at 20 °C, in millionths per kelvin: brass 19, steel 11.0-13.0).

14. Miles Free, “Adjusting to Unleaded”, Production Machining, 21 May 2009: productionmachining.com (an 80 percent machinability rating for no-lead C69300).