CNC Machining Copper
Copper is specified for one reason: it conducts. Electrically and thermally it beats everything else we machine, which is why bus bars, heat sinks, electrodes and RF components are made from it. It is also, for a soft metal, genuinely awkward to cut well — it smears rather than chips, and a good surface finish takes deliberate effort.
Grades we machine
C110 is the standard choice where conductivity is the point. The alloyed grades trade some conductivity for strength or machinability.
| Grade | Best for | Notes |
|---|---|---|
| C110 ETP copper | Bus bars, heat sinks, electrical terminals, EDM electrodes | The standard high-conductivity copper. Soft and gummy to machine |
| C101 oxygen-free copper | High-vacuum, RF and cryogenic components | Very high purity and conductivity; used where oxygen content matters |
| C145 tellurium copper | Parts that need conductivity and must be machined in quantity | Far better machinability than C110 at a small cost in conductivity — usually the right compromise |
| Beryllium copper | Springs, contacts, non-sparking tools | High strength and good conductivity; requires careful handling and heat treatment |
Soft does not mean easy
Copper is ductile and does not want to break into chips. It forms long stringy swarf that wraps around the tool, and it smears under a dull edge instead of shearing cleanly, which leaves a torn surface rather than a machined one. The fixes are sharp uncoated tooling with high positive rake, real chip loads rather than light passes, and plenty of coolant.
If your part needs conductivity and quantity, tellurium copper (C145) is worth knowing about: it machines several times more easily than C110 for a small loss in conductivity. On a production run that trade is usually worth making, and it is the kind of change we would raise at quotation.
Copper also oxidises quickly. A bright machined surface will dull within days in normal air, so parts that must arrive bright need lacquering, plating or sealed packing.
| At a glance | |
|---|---|
| Typical tolerance | ±0.01 mm (±0.0004 in), harder to hold on thin sections because the material is soft |
| Machinability | Poor for C110, good for C145 tellurium copper |
| Conductivity | The highest of any material here, electrically and thermally |
| Standard finishes | Nickel or tin plating, clear lacquer, tumbling |
| Certificates | EN 10204 3.1 on request |
Three notes on copper parts
Consider tellurium copper for volume
If the drawing says C110 and the part is going into production, ask whether C145 is acceptable. The conductivity difference is small; the machining difference is not.
Plan for oxidation
Bare copper dulls in days. Decide at the order whether the part is plated, lacquered or simply packed sealed — it is not something to sort out after delivery.
Keep threads and thin walls generous
Copper is soft: fine threads strip more easily and thin walls deflect. A slightly heavier section costs almost nothing and removes a failure mode.
Finishes that work on copper
Copper is normally plated or lacquered, both to stop oxidation and to protect the conductive surface.
Finishing is done by partner shops we specify and inspect for — we do not run plating or coating tanks ourselves. How we handle finishing →
Send the conductor drawing
Send the drawing and the grade, or the drawing and a sentence about what the part has to survive. You get a price, a lead time, and an engineer’s note on anything that will fight the tolerances.