Tungsten grades / Pure tungsten
Pure Tungsten (99.95% W)
The highest melting point of any metal, and the most brittle of the four grades on this site to machine.
Pure tungsten is at least 99.95% tungsten metal, made by pressing and sintering powder and sometimes forged or rolled afterward. It is not the material most buyers mean when they write "tungsten" on a drawing (that is usually tungsten heavy alloy), so state "pure tungsten" or "99.95% W" explicitly if that is what your application needs.
| Property | Typical value |
|---|---|
| Density | Around 19.3 g/cm³, typical |
| Hardness | Typically cited around 350 HV (Vickers) in annealed wrought form, harder than most unhardened tool steels |
| Magnetic behavior | Non-magnetic |
| Typical tolerance | ~±0.025 mm milled, tighter by grinding |
Typical density
Pure tungsten runs around 19.3 g/cm³, typical. That is the densest of the four grades on this site, slightly above tungsten heavy alloy's 17.0 to 18.5 g/cm³ range. For a shielding or ballast part, this is the grade with the least volume for a given mass, though heavy alloy is chosen far more often because it machines with far less difficulty for a similar density.
Hardness and why brittleness matters more
Pure tungsten is very hard for a pure metal, typically cited around 350 HV (Vickers) in annealed, wrought form, harder than most unhardened tool steels. But hardness is not the property that drives how it is machined. Pure tungsten is brittle at room temperature: a cutting edge tends to fracture the material rather than shear it, which shows up as chipped edges, cracked thin walls and a rougher surface than the same operation would leave on a ductile metal. This is the property to design around, more than the hardness number itself.
Magnetic or non-magnetic
Pure tungsten is non-magnetic on its own, the same as tungsten carbide. Magnetism only becomes a design question for tungsten heavy alloy, where the binder metal (iron or copper) determines the part's magnetic behavior.
How it machines
Pure tungsten is milled and turned on standard CNC equipment with carbide tooling, but with more care than heavy alloy: rigid setups, sharp tools and light finishing passes reduce the chipping and cracking that brittleness causes. Where the design allows it, shops cut slots, holes and other features before thinning a part to its final wall section, since more stock left in the part means more rigidity during those operations. The tightest features, and the finest surface finishes, are often finished by grinding or wire EDM rather than pushed past what milling reliably holds. Thin heat shields and crucible walls are the parts most likely to need this sequencing.
Typical achievable tolerance
Standard milled tolerance on pure tungsten runs around ±0.025 mm, typical. Tighter tolerances, and finer finishes than a milled surface reliably delivers, are held by a finishing grinding pass rather than by pushing milling past its practical limit.
Typical applications
- Heat shields, boats and crucibles inside vacuum and inert-atmosphere furnace hot zones
- High-temperature fixtures that see repeated thermal cycling above the working range of tungsten heavy alloy
- Tungsten electrodes for GTAW (TIG) welding
- X-ray tube targets and anodes
A note on ASTM B777
ASTM B777 covers tungsten heavy alloy, not pure tungsten. It does not apply here. If your RFQ or drawing references a B777 class alongside "pure tungsten," check whether the part actually needs the alloy's toughness (in which case heavy alloy is the right grade) or pure tungsten's heat resistance (in which case B777 does not apply and a purity spec, such as 99.95% W, is what matters instead).
Sources
Have a pure tungsten part to source? Get matched with a shop that cuts this grade.
Related: machining pure tungsten vacuum furnace components and pure tungsten vs heavy alloy vs carbide.