Guides / Materials

Tungsten Copper Machining for Electrodes and Contacts

Updated September 26, 2026 · Reviewed September 26, 2026

Tungsten copper is the easiest of the tungsten materials to machine, and it is worth understanding on its own terms rather than lumping it in with pure tungsten or heavy alloy. This guide covers how it cuts, what ratio to specify, typical tolerances and features, and where it fits among the other tungsten grades.

What tungsten copper actually is

Tungsten copper is made by pressing and sintering a porous tungsten skeleton, then infiltrating it with molten copper, typically 10 to 30% copper by weight. The result is a composite that keeps much of tungsten’s density and arc erosion resistance while gaining copper’s thermal and electrical conductivity. It is written as a ratio, such as W70Cu30 (70% tungsten, 30% copper) or W90Cu10, and the ratio is what a shop or mill needs to know before quoting, since it changes density, conductivity and how the material machines.

Why it machines easier than pure tungsten

Pure tungsten is brittle at room temperature and tends to fracture rather than shear under a cutting tool, which causes the chipping and cracking covered in most tungsten machining guides. Tungsten copper does not have this problem in the same way. The copper phase gives the material enough ductility that it cuts more like a hard brass or bronze, producing a cleaner chip and a better as-machined surface finish. Shops that avoid pure tungsten for fine detail work often have no hesitation running tungsten copper on the same equipment.

Turning, milling, drilling and threading

Tungsten copper turns and mills on standard CNC equipment with carbide tooling, at cutting parameters closer to a hard copper alloy than to pure tungsten. It takes fine detail well, which is exactly why it is chosen for parts like EDM electrodes that need precise geometry. Drilling and tapping are routine, without the small-hole cracking risk that pure tungsten carries, and standard taps cut clean threads at parameters similar to a hard copper alloy rather than requiring the caution a pure tungsten thread demands.

The two things to watch are burrs, since the copper phase can raise a burr the way copper alloys do, and consistency of the ratio itself. A part machined from stock with an inconsistent tungsten-copper ratio can vary in density and conductivity even if the dimensions are correct, which matters for applications where electrical or thermal performance is part of the spec.

Typical tolerances

±0.01 to ±0.02 mm is common on turned and milled tungsten copper features, similar to or slightly tighter than what is typical for tungsten heavy alloy. Critical faces on electrodes, where geometry directly affects the EDM process, are sometimes finished by grinding for the tightest tolerance.

Feature-level guidance for electrode and contact drawings

Feature	Typical tolerance	Notes
Electrode working face	±0.01 mm, tighter by grinding on critical geometry	Directly affects EDM spark gap and finish
Shank or mounting diameter	±0.01 to ±0.02 mm	Standard turning tolerance, rarely the limiting feature
Threaded mounting features	Routine, standard tap classes	No special caution needed compared with pure tungsten
Contact wear face	Depends on application, often ±0.02 mm or looser	Wear allowance usually matters more than tight tolerance

Where tungsten copper is used

• EDM electrodes, where the material’s wear resistance under arcing combines with copper’s conductivity to erode predictably and hold detail through a production run.
• Welding electrodes, for the same arc erosion resistance in a different process.
• Electrical contacts, where the material must carry current and resist the wear of repeated switching or arcing.
• Heat spreaders, using copper’s thermal conductivity alongside tungsten’s lower thermal expansion, which helps the material match against silicon or ceramic substrates in electronic assemblies.

Choosing a ratio

Higher tungsten content, such as W90Cu10, favors density, hardness and arc erosion resistance, at the cost of some conductivity. Higher copper content, such as W70Cu30, favors thermal and electrical conductivity at the cost of some hardness. For EDM electrode work, W70Cu30 and W80Cu20 are the most commonly specified ratios, balancing erosion resistance against machinability and conductivity. If you are not sure which ratio fits your application, state the property that matters most, conductivity, hardness or density, and let your shop or mill recommend a starting point.

Comparing tungsten copper to the other grades

Grade	Machinability	Typical use
Pure tungsten	Brittle, needs careful setup	Extreme heat resistance
Tungsten heavy alloy	Cuts like hard cast iron	Shielding, counterweights
Tungsten copper	Cuts like hard brass or bronze	EDM electrodes, electrical contacts

Common mistakes when specifying tungsten copper parts

• Writing “tungsten copper” without a ratio. The ratio changes density, conductivity and machining behavior enough that a shop cannot quote accurately without it.
• Over-tolerancing faces that only need a wear allowance. Contact wear faces rarely need the same precision as an electrode’s working geometry.
• Skipping the conductivity or density requirement when it actually matters. If your application depends on a specific electrical or thermal property, say so, rather than assuming any ratio in the right general range will perform the same.
• Assuming tungsten copper and heavy alloy are interchangeable. They serve different purposes. Heavy alloy is chosen for density and mechanical toughness, tungsten copper for conductivity and arc resistance, and swapping one for the other usually means the part no longer does its job.
• Ignoring burr formation on drawings with a sharp edge requirement. If a fine edge or corner matters to the part’s function, note it explicitly, since the copper phase raises burrs more readily than a pure refractory metal would and a shop needs to plan a deburring step accordingly.

When testing makes sense

Most tungsten copper parts ship without any special testing beyond standard dimensional inspection, since geometry rather than a precise material property is usually what matters. The exception is a part where conductivity or density is written into the functional spec, such as certain electrical contacts. In that case, ask your shop whether they test in-house or send samples to an outside lab, since that affects both cost and lead time, and state the acceptance criteria clearly rather than leaving it implied.

What to include in the RFQ

1. The exact ratio, such as W70Cu30, rather than just “tungsten copper.”
2. A STEP file and dimensioned drawing, with tolerances on the features that matter, particularly any geometry critical to the electrode or contact function.
3. Quantity, since repeat electrode orders may justify a near-net blank the same way heavy alloy parts do.
4. Conductivity or density requirements, if the application depends on a specific electrical or thermal property.

When your drawing is ready, send your RFQ and we match it with shops experienced in tungsten copper work. For how the other tungsten grades compare, see what each tungsten grade allows. For the machining side of heavy alloy specifically, see tungsten heavy alloy machining.

See also: W80Cu20 tungsten copper, for the properties and uses of the most common ratio.

Frequently asked questions

Sources

• Wikipedia - Gas tungsten arc welding
• Wikipedia - Tungsten
• Wikipedia - Electrical discharge machining

Keep reading

• Molybdenum Copper or Tungsten Copper: Choosing a Heat Spreader Material
• Doped Tungsten: Lanthanated and Potassium Doped Grades and Their Parts