Copper CNC Machining Services
C11000 electrolytic tough pitch copper carries 100 percent IACS electrical conductivity and about 390 W/m·K thermal conductivity, and is the standard for busbars, heat sinks and RF components.
C11000 ETP and C10100 oxygen-free copper
Tolerances to ±0.05 mm on critical features
Plating, passivation and polishing available
What Is Copper?
Why copper is difficult to machine, what that does to lead time and cost, and when no substitute will do.
C11000, also called electrolytic tough pitch or ETP copper, is a minimum 99.9 percent pure copper with a small, controlled oxygen content. It carries 100 percent IACS electrical conductivity and roughly 390 W/m·K thermal conductivity, roughly twice that of aluminium and more than twenty times that of stainless steel. Where a design is limited by heat or by electrical resistance, nothing else performs like copper.
The machining trade-off
Pure copper is soft, gummy and work hardening, with a machinability rating of only 20 against brass at 100. It forms long continuous chips, tends to build up on the cutting edge, and holds heat poorly at the tool tip. In practice that means sharp polished carbide, generous rake angles, lower speeds than brass and continuous chip control. Cycle times are longer than for brass or aluminium, and that is the price of the conductivity.
Grades and service conditions
C11000 is the general-purpose grade. C10100 oxygen-free copper is specified for vacuum, glass-to-metal seals and any service above about 370 °C in a reducing atmosphere, where the oxygen in ETP copper causes hydrogen embrittlement. Tell us the service environment and we will recommend the grade, or suggest a copper alloy with better machinability if the conductivity margin allows.
Related capabilities: CNC Machining, CNC Milling, CNC Turning, 5-Axis Machining. Dimensional limits, thread rules and surface roughness grades are listed on the tolerances and specifications page, and volume-based routing is covered under production solutions.
Copper Mechanical Properties
Typical values at room temperature for the condition most often machined. Use them for material screening, then confirm against the mill certificate for the exact heat and product form.
| Property | Typical value |
|---|---|
| Density | 8.94 g/cm³ |
| Ultimate tensile strength | 220 MPa annealed, 290 MPa half hard |
| Tensile yield strength | 69 MPa annealed, about 250 MPa half hard |
| Elongation at break | 45% annealed, about 20% half hard |
| Elastic modulus | 117 GPa |
| Hardness | 35 to 45 HRB in half hard temper |
| Thermal conductivity | About 390 W/m·K at 20 °C |
| Electrical conductivity | 100% IACS minimum |
| Melting point | 1083 °C |
| Machinability rating | 20, against C36000 brass at 100 |
Typical room-temperature values compiled from public ASM, MatWeb and mill datasheets. Actual values vary with temper, section thickness and product form; request the EN 10204 3.1 certificate for critical applications.
Machining Characteristics of Copper
How the material behaves in the cut, and what that means for tooling, fixtures, cycle time and achievable tolerance.
Gummy chip formation
Pure copper produces long continuous chips. Sharp polished carbide, chip breakers and high-pressure coolant are required to clear the cut.
Built-up edge control
Material smears onto a dull edge and then tears the surface. Tools are changed on a strict schedule to protect finish.
Work hardening
Like austenitic stainless, copper hardens if a tool rubs. Keep feed constant and never dwell, especially in corners and when drilling.
Thermal distortion
Very high conductivity moves heat into the part quickly, so clamping and coolant strategy must be symmetrical to avoid bowing thin sections.
Burring
Soft copper leaves heavy burrs on exit edges. Plan for a dedicated deburr pass or a media finishing step on every part.
Joining and plating
Copper is readily soldered, brazed and plated with nickel, tin or silver; it is difficult to arc weld without a controlled process.
Design and Machining Checklist
Practical rules that reduce cost and scrap on Copper parts. Share them with your design team before the drawing is frozen.
- Expect a longer cycle time and a higher unit cost than brass; budget for it at the design stage.
- Specify C10100 oxygen-free copper for vacuum service or any high-temperature reducing atmosphere.
- Add a deburring allowance or a media finishing step; copper burrs are soft, tenacious and easy to miss by hand.
- Design clamping pads and coolant access into the part to control thermal growth during machining.
- Nickel or tin plating prevents surface oxidation and tarnish on parts that must keep a stable contact resistance.
- If conductivity can drop to roughly 80 percent IACS, ask about a free-machining copper alloy instead.
Surface Finishing Options
Finishes are selected for corrosion resistance, wear, appearance, electrical behaviour or cleanliness. Specify only what the function needs.
As-Machined
Ra 1.6 to 3.2 µm with visible tool marks. Acceptable for busbars and internal current paths.
Nickel Plating
5 to 25 µm electrolytic nickel that prevents oxidation and keeps contact resistance stable in service.
Tin Plating
Solderable, food-safe coating widely used on busbars, terminals and electrical contact surfaces.
Silver Plating
The highest conductivity surface finish, used for RF components, high-frequency contacts and microwave hardware.
Passivation and Anti-tarnish
Benzotriazole treatment that keeps the bright copper colour during storage and assembly.
Polishing
Mechanical polish to a bright or mirror finish for decorative elements and low-emissivity thermal surfaces.
Typical Applications
Where Copper is most often specified, and why it wins against the alternatives.
Busbars and power distribution
Current-carrying bars, links, shunts and terminal blocks for switchgear, battery packs and power electronics.
Heat sinks and cold plates
Finned heat sinks, liquid cold plates and spreader blocks for power electronics, lasers and LED assemblies.
RF and microwave components
Waveguide parts, cavity resonators, antenna elements and shielding enclosures where surface conductivity sets performance.
Welding and resistance equipment
Electrode holders, conductor arms, secondary circuit components and cooling blocks.
Electrical contacts and terminals
Contact bodies, clamps, lugs and connector hardware that need low and stable contact resistance.
Process and chemical plant
Heat exchanger components, chlorine cell parts and vessel fittings that exploit copper corrosion behaviour.
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