COPPER, BRASS & BRONZE MACHINING SERVICES
Copper alloys cover the widest machinability range of any family we run. C360 free-cutting brass is the fastest-machining metal in the shop chips break into dust and the material is the benchmark against which every other copper alloy is rated. C110 copper is at the other end: gummy, burr-prone, and often more work to deburr than to cut. Same family, entirely different jobs.
Steelcrest runs copper, brass and bronze across 28 CNC lathes, four Swiss lathes with 12-foot bar capacity, dual-spindle and live-tool turning platforms, and a full milling department. Turning holds ±0.0005" as standard and ±0.0002" in precision turning.
| Alloy | Machinability | Character | Typical use |
|---|---|---|---|
| C110 / C101 copper | 20 | Extremely gummy and ductile. C101 is the oxygen-free grade. | Electrical terminals, bus components, heat exchangers, vacuum and semiconductor parts. |
| C360 brass | 100 — the baseline | The easiest metal in the shop. Chips break into dust. | Fittings, valve bodies, small turned parts at volume. |
| C464 naval brass | 30 | Much tougher than C360; machines more like a bronze. | Marine hardware and fittings. |
| C932 bearing bronze | 70 | Leaded tin bronze. The standard bushing material. | Bushings, sleeves and bearings, honed to size. |
| C954 aluminum bronze | 60 | Strong, tough, galling-resistant — but work-hardens and is abrasive. | Wear plates, dies, bushings and high-load bearing details. |
These figures are on the Copper Development Association scale, where C36000 free-cutting brass is 100. This is a different baseline from the AISI percentages used for steel, and the two are not comparable C360 sits above 300 percent on the steel scale.
| Process | Tolerance | Surface finish |
|---|---|---|
| CNC turning, standard | ±0.0005" | Up to 8 Ra |
| Precision turning | ±0.0002" | Up to 8 Ra, polishing available |
| CNC milling, 3- and 4-axis | ±0.001" (excluding true-position callouts) | 32 Ra side / 63 Ra face |
| 5-axis milling | ±0.001" linear · ±0.002–0.003" rotational · ±0.003" tilted-hole | 32 Ra |
| INTEGREX / Hyper Quadrex mill-turn | ±0.0005" | 32 Ra |
| OD, surface and Blanchard grinding | ±0.0005" to ±0.0002" | Up to 8 Ra |
| Wire EDM | ±0.0005" to ±0.0002" | 16–32 Ra, fine to 8 Ra |
NOTE*: On C110 copper, ±0.0002" precision turning is marginal ductility, smearing and burr formation limit it more than the machine does. Deburring on copper is a real operation with real cost, and we quote it as one rather than absorbing it and discovering it later.
C360 brass and free-machining copper alloys are what bar-fed turning was designed for, and it is the capability that separates a machine shop from a marketplace on this material. We run four Swiss lathes handling bar up to Ø1.5" with 12-foot bar capacity, two dual-spindle lathes at Ø10" × 8" for two-operation parts complete in one cycle, three live-tool lathes for cross-drilling and milling without a second setup, and three Y-axis lathes with six inches of Y travel for off-centre features.
For a fitting, valve body or turned detail in C360 at production volume, that combination produces a finished part off the machine turned, cross-drilled, milled, parted and dropped with no secondary operation. That is where the cost comes out of the part.
Larger work runs on 28 conventional CNC lathes to Ø26" × 160", with 36 vertical machining centers, eight horizontals and five 5-axis verticals for prismatic and wear-plate work, and honing to Ø8" for finished bushing bores.
Four grades, four completely different personalities in the cut, and knowing which one your part needs is most of the battle.
C110 and C101 are extremely gummy and ductile long stringy chips, heavy burrs and smearing. Razor-sharp, high-positive-rake polished tools with rake angles between 20 and 40 degrees, light depths of cut and lubricating coolant. The single biggest lever is temper: half-hard H02 copper machines far better than annealed O60 material. Never buy annealed copper for machining, and if your supplier sends it, tell us before we start.
C360's machinability comes from its lead content, and that lead content is increasingly restricted RoHS, drinking-water statutes and NSF/ANSI 61 all push toward substitution. The low-lead replacements such as C69300 and C87850 machine noticeably worse, somewhere in the 60 to 80 range on the copper scale, which changes cycle time and therefore price. If your part is heading into a potable-water or regulated application, raise it at RFQ and we will quote the substitute rather than quoting C360 and surprising you later.
Aluminum bronze is strong, tough and galling-resistant which is exactly why it is specified for wear plates and dies — but it work-hardens and its aluminium-oxide skin is abrasive. Carbide tooling, rigid setups and positive rake are required, and tool wear rather than machine capability drives dimensional drift within a run.
C932 bearing bronze bushings are normally sized or burnished after press-fit rather than machined to final bore beforehand, because the press-fit closes the bore. If your drawing calls out a finished bore dimension on a bushing that will be pressed in, tell us the installed requirement instead and we will work to that.
Steelcrest Precision machines copper, brass, and bronze components for consumer products, food and beverage equipment, automotive, and material handling systems, where conductivity, corrosion resistance, and low friction earn these alloys their place.
We also machine copper alloys for electrical, plumbing and marine customers who reach us directly.
Send the drawing and the quantity. We will come back with a real number, a real lead time, and if there is a better material or condition for what the part has to do — we will tell you that too.
Yes four Swiss lathes handling bar to Ø1.5" with 12-foot bar capacity, plus dual-spindle, live-tool and Y-axis turning platforms. For C360 brass fittings and turned details at volume, that combination produces a complete part off the machine with no secondary operation.
Yes. If the part is going into a potable-water or regulated application, tell us at RFQ and we will quote the appropriate low-lead grade. Be aware that they machine noticeably worse than C360 somewhere in the 60 to 80 range against C360 at 100 — which affects cycle time and price.
C110 copper sits at 20 on the copper scale against C360 brass at 100. It is gummy and ductile, producing long stringy chips, heavy burrs and smearing, and the deburring is frequently more work than the cutting. It is a real cost, and we quote it as a separate operation rather than hiding it.
Half-hard, H02 temper. Annealed O60 copper machines significantly worse and there is rarely a good reason to buy it for a machined part.
Usually the better approach is to size or burnish after press-fit, since the press-fit closes the bore. Tell us the installed requirement rather than a pre-fit bore dimension and we will work to that.
Through qualified partners — nickel, tin, silver and gold plating for electrical parts, and bright dip, passivation or clear lacquer on brass to prevent tarnish.
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