Tungsten copper has a reputation for being difficult to machine. Mostly, that reputation belongs to pure tungsten — sintered, hard, and genuinely abrasive. Infiltrated W/Cu is a different material to cut: a tungsten skeleton filled with copper, and it behaves closer to a hard bronze than to a refractory metal. This guide covers what shops need to know before putting W/Cu on a lathe or a machining center.
What the composite cuts like
Infiltrated W/Cu is a two-phase material, and that is the key to everything about machining it. The copper phase cuts easily; the tungsten skeleton is what limits your speeds and dulls your tools. Practical consequences:
- Carbide tooling throughout. HSS works briefly and then does not; coated carbide is the economical default for turning, milling and drilling.
- Positive rake angles. The copper phase tears rather than shears cleanly if you push it with a negative geometry — sharp, positively raked edges leave a better surface.
- Flood coolant. Heat that stays in the cut smears copper over the tungsten skeleton and glazes the surface. Coolant keeps the chip clear and the finish honest.
- No grinding required for ordinary turning, milling or drilling. Surface grinding is reserved for faces that need it dimensionally, not because the material demands it.
Two habits separate good W/Cu work from scrapped blanks: take light finishing passes so the copper phase is not torn out of the surface, and support slender sections properly. The composite is stiff, but it chatters on thin, poorly clamped work just like any dense metal.
Starting parameters
The tables below are shop-floor starting points for infiltrated W/Cu at 70/30 and 75/25, on a rigid machine with coated carbide and flood coolant. They are a place to begin, not a guarantee — copper content, blank porosity and your own rigidity all shift the sweet spot, so take a test cut and adjust from there. The higher figure in each range suits the leaner 75/25 grade.
Turning
| Operation | Surface speed | Feed | Depth of cut | Insert | Target Ra |
|---|---|---|---|---|---|
| Rough turning | 60–90 m/min | 0.15–0.30 mm/rev | 1.5–3.0 mm | K10 / C2, positive rake | 1.6–3.2 µm |
| Finish turning | 90–140 m/min | 0.05–0.12 mm/rev | 0.2–0.5 mm | K10, sharp edge, small nose radius | 0.8–1.6 µm |
| Facing a wheel face | 80–120 m/min | 0.08–0.15 mm/rev | 0.3–0.8 mm | K10 | 1.2–2.0 µm |
Milling and drilling
| Operation | Surface speed | Feed | Notes |
|---|---|---|---|
| Peripheral milling | 60–100 m/min | 0.05–0.12 mm/tooth | 4-flute carbide, climb cut for finish |
| Slotting / pocketing | 50–80 m/min | 0.04–0.08 mm/tooth | Ramp in, never plunge straight down |
| Drilling | 25–45 m/min | 0.05–0.12 mm/rev | Peck deeper than 2× diameter; clear chips |
| Reaming / finish boring | 15–25 m/min | 0.10–0.25 mm/rev | Size comes from here, not from the drill |
| Tapping | 8–15 m/min | — | Sharp machine tap, cutting oil, no dry run |
Three numbers are worth remembering out of all of that. Surface speed above roughly 150 m/min is where copper starts smearing across the tungsten skeleton and the finish goes glossy and torn. Finish depth of cut below 0.2 mm rubs rather than cuts and work-hardens the surface. And drilling without pecking is the single most common cause of a broken drill in W/Cu — the chip does not clear, and dense material punishes the retraction.
If a cut is squealing and the insert is wearing on the flank rather than the nose, you are too fast for the rigidity you have. Drop speed before you change geometry.
Threading W/Cu
Cutting a clean thread in tungsten copper is a quality-control problem more than a machining problem. The copper phase tears easily, and a torn thread root becomes a stress riser exactly where vibration concentrates — a welding gun shank, a threaded electrode stud, a fixture bolt.
Practical threading guidance:
- Cut threads on a conventional lathe with sharp carbide inserts; single-point threading gives the cleanest roots in the composite.
- Gauge every batch with go/no-go thread gauges — a thread that gauges true on arrival is the only thread that screws into your holder the first time.
- Metric and UNC/UNF forms are routine; special forms, left-hand threads and tapered shanks are all cut to drawing.
- Match the thread fit class your mating holder was designed around. In welding guns the threaded joint carries current, force and tip-change release all at once, so fit class is not cosmetic.
If your consumption shows thread damage rather than face wear, the fix is usually seating practice or holder design — not the alloy. When you are writing the drawing rather than reading it, how to specify threaded tungsten copper electrodes covers thread callouts, shoulder geometry and torque values.
Drilling and small holes
Drilling behaves like a free-machining bronze at reduced surface speed. Use sharp carbide drills, peck on deeper holes to clear chips, and expect accurate, clean bores at typical workshop feeds. Precision bores — the H7 wheel bores that have to drop onto an existing shaft — are finish-bored or reamed rather than drilled to size, which is standard practice for any metal but worth stating: bore tolerance lives or dies on the finishing operation, not the drill.
When to machine it yourself — and when not to
Buying rods and blocks and machining in-house makes sense when you cut caps, shanks and simple facings on short notice and your machine time is cheap. Stock shapes in both W/Cu 75/25 and 70/30, rough-machined or ground, exist exactly for that workflow — how to buy tungsten copper rods and blocks covers the sizes, the delivery condition and how a stock order is quoted.
But run the numbers honestly for finished parts. A wheel with a keyed bore, a bevel profile and a runout requirement needs tooling, setup, gauging and balancing — and dense W/Cu punishes packaging and handling mistakes in transit. For anything beyond simple facings, finished parts to drawing often cost less than stock plus your shop time, and they arrive with dimensional records — ordering custom electrode wheels walks through what a drawing package needs to contain.
Get stock or get it finished
ArcTung supplies rods, blocks and blanks in both grades with no MOQ — or machines your drawing complete, standard shapes in 10–14 days, custom work in 20–25 days, samples in 10 days or less. Write to sales@arctung.com with your part or your stock list and we will tell you honestly which route costs less.