Copper Material Grades
Copper is machined for conductivity, and every grade on this page is a different answer to the same question: how much conductivity are you willing to trade for something else — strength, machinability, or purity. This is the reference for the grades we cut.
Copper grades we machine
Conductivity is quoted as %IACS, where pure annealed copper is defined as 100%. The practical decision for most machined parts is C110 against C145.
| Grade | What it is | Best for | Machinability |
|---|---|---|---|
| C110 ETP | Electrolytic tough pitch, about 100% IACS | Bus bars, terminals, heat sinks, EDM electrodes | Poor — gummy, strings, smears |
| C101 / C102 OFE, OFHC | Oxygen-free, very high purity | Vacuum, RF, cryogenic and semiconductor parts | Poor, same as C110 |
| C145 tellurium copper | Tellurium added for machinability, around 90% IACS | Conductive parts made in quantity | Good — several times easier to cut than C110 |
| C147 sulphur copper | Sulphur added, around 95% IACS | Conductive parts where purity matters more than in C145 | Good |
| C172 beryllium copper | Age-hardening high-strength alloy | Springs, electrical contacts, non-sparking tools, moulds | Moderate; heat treatable to high strength |
| C182 chromium copper | Chromium added, around 80% IACS | Resistance welding electrodes, high-strength conductors | Good; holds strength when hot |
The trade nobody tells you about until it is too late
Pure copper is soft, ductile and does not want to break into chips. It forms long stringy swarf, it smears under a worn edge instead of shearing, and the surface finish you get from an unconsidered setup is torn rather than machined. Sharp uncoated high-rake tooling, real chip loads and plenty of coolant are what make C110 behave.
The important commercial point is that C145 tellurium copper machines several times faster than C110 for roughly a 10% loss in conductivity. On a single prototype that hardly matters. On a production quantity it can halve the price of the part. If your drawing says C110 and the design does not actually need the last 10%, this is the single most useful change you can make, and we will raise it at quotation.
All bare copper oxidises quickly — a bright machined surface dulls within days. That is cosmetic rather than structural, but it needs deciding: plating, lacquer, or sealed packing.
| At a glance | |
|---|---|
| Typical tolerance | ±0.002 mm (±0.0001 in); harder on thin sections because the material is soft |
| Conductivity | Highest of any material we machine, electrically and thermally |
| Machinability | Poor for pure grades, good for C145 and C182 |
| Standard finishes | Nickel or tin plating, clear lacquer, tumbling |
| Certificates | EN 10204 3.1 on request |
Three notes on copper parts
State the minimum conductivity, not the grade
If you tell us the electrical requirement rather than copying a grade from an old drawing, we can often propose C145 and save you real money on the batch.
Decide how the part is protected
Bare copper dulls in days. Plating, lacquer or sealed packing — pick one at the order rather than after delivery.
Keep sections and threads generous
Copper is soft: fine threads strip, thin walls deflect. A slightly heavier section removes a failure mode for almost no cost.
Finishes that work on copper grades
Copper is plated or lacquered to stop oxidation and protect the conductive surface.
Tell us the conductivity you actually need
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.