Reference Chart
Tungsten & Tungsten Alloy Feeds & Speeds Chart
Quick-look reference data for tungsten heavy-alloy milling, plus the decision points that tell you when pure tungsten or sintered carbide should leave conventional machining and move to grinding or EDM.
Direct answer: tungsten heavy alloy can be milled cautiously, but pure tungsten and sintered carbide often belong in grinding or EDM before a feeds-and-speeds calculator.
Use this chart for tungsten process boundaries and first-pass heavy-alloy values; RPM, feeds/speeds, and drilling calculators only apply after conventional cutting is still realistic.
Need To Turn This Chart Into RPM & Feed?
Use a calculator only after this chart says the job is still a conventional tungsten heavy-alloy milling problem. Pure tungsten and sintered tungsten carbide often need grinding or EDM instead of a generic feeds-and-speeds workflow.
Formula Handoff
Formula handoff: qualify the tungsten process first, then convert SFM to RPM only if conventional cutting still applies. Heavy alloy, pure tungsten, and sintered carbide should not share one calculator path unless the process boundary is already settled.
Release checks before calculator use
- Separate tungsten heavy alloy from pure tungsten and sintered tungsten carbide before choosing SFM.
- Evaluate grinding or EDM first when brittle fracture, dust, or carbide hardness controls the job.
- Use the RPM, feeds/speeds, or drilling calculator only after conventional cutting remains credible.
Worked example and release boundary
Worked example: a 0.5 in cutter at 120 SFM in 90% tungsten heavy alloy converts to about 920 RPM; at 0.002 in/tooth and four flutes, feed is about 7.3 IPM before rigidity, edge chipping, dust, and heat checks.
Release boundary: do not use this table for pure tungsten, sintered tungsten carbide, grinding, EDM, or drilling until the process route is confirmed; those cases are not generic milling calculator problems.
Reference handoff
Tungsten table handoff
Use this chart for tungsten reference ranges, then route RPM, general cutter math, or drilling through dedicated workflows.
Best starting point
Tungsten and heavy-alloy reference values for first-pass comparison.
Branch when
RPM conversion, broad cutter setup, and holemaking need calculator validation.
Tungsten Heavy Alloys (Densimet / Inermet / W-Ni-Fe)
90-97% tungsten with nickel-iron or nickel-copper binder. These are the most machinable tungsten materials — the binder provides ductility. Used for counterweights, radiation shielding, and aerospace balance weights. Density: 17.0-18.5 g/cm³.
| Grade | Operation | SFM (Coated Carbide) | Chip Load (1/2" EM) |
|---|---|---|---|
| 90% W (17.0 g/cm³) | Roughing | 80 - 150 | 0.002" - 0.004" |
| 90% W (17.0 g/cm³) | Finishing | 120 - 200 | 0.001" - 0.002" |
| 97% W (18.5 g/cm³) | Roughing | 50 - 100 | 0.0015" - 0.003" |
| 97% W (18.5 g/cm³) | Drilling | 30 - 80 | 0.001" - 0.003"/rev |
The roughing and finishing rows are the main workflow here. The drilling row is reference-only on this chart; validate any real heavy-alloy drilling setup in the drilling calculator.
Pure Tungsten (99.95% W)
Extremely brittle at room temperature (DBTT ~200-400°C). Conventional milling is possible but challenging — micro-fracture at the cutting edge is constant. Most pure tungsten is shaped by grinding, EDM, or hot forming followed by finish grinding.
| Operation | SFM (Coated Carbide) | Chip Load (1/2" EM) | Notes |
|---|---|---|---|
| Roughing | 30 - 60 | 0.001" - 0.002" | Light DOC, rigid setup mandatory |
| Finishing | 40 - 80 | 0.0005" - 0.001" | Diamond-coated preferred |
| Grinding (Preferred) | 4000 - 6000 | 0.0002" - 0.001" | Diamond wheel, flood coolant |
Tungsten Carbide (WC-Co Cemented Carbide)
Sintered tungsten carbide (WC + cobalt binder) is the material that cutting tools themselves are made from. Machining carbide with carbide is nearly impossible — EDM and diamond grinding are the primary methods. CBN and PCD tools can profile green (unsintered) carbide.
| Condition | Method | Speed | Notes |
|---|---|---|---|
| Green (Pre-Sinter) | Milling (CBN) | 200 - 500 SFM | Allowance for ~20% sintering shrinkage |
| Sintered (90+ HRA) | Diamond Grinding | 4000 - 6000 SFM | Resin or metal-bond diamond wheel |
| Sintered | Wire EDM | — | Primary method for complex shapes |
| Sintered | Sinker EDM | — | Cavities and blind features |
Tungsten Machining Realities
Pure tungsten and sintered tungsten carbide are among the most difficult materials to machine conventionally.
- Brittleness: Pure tungsten fractures like glass below its ductile-brittle transition temperature (~200-400°C). Any interrupted cut or chatter risks part cracking.
- Tool wear: Tungsten heavy alloys wear carbide tools 3-5x faster than steel at equivalent SFM. Budget for frequent tool changes.
- EDM first: For sintered WC and pure tungsten complex shapes, always evaluate wire EDM before conventional milling. EDM is often faster and cheaper.
- Health: Tungsten dust is a respiratory irritant. OSHA PEL: 5 mg/m³ for insoluble tungsten, 1 mg/m³ for soluble tungsten compounds.
Frequently Asked Questions
Can you machine tungsten on a CNC mill?
Tungsten heavy alloys (Densimet/Inermet, 90-97% W): yes, with coated carbide at 50-150 SFM. Pure tungsten: barely — it's extremely brittle and better suited to grinding or EDM. Sintered tungsten carbide: no — use diamond grinding or EDM.
What is the best way to machine sintered tungsten carbide?
Wire EDM for profiles and complex shapes. Diamond grinding for flat surfaces and OD/ID. Green machining (pre-sinter) with CBN for near-net-shape blanks that are finish-ground after sintering (account for ~20% shrinkage).
What is the difference between tungsten and tungsten carbide?
Pure tungsten is a metal (19.3 g/cm³, brittle). Tungsten carbide (WC) is a ceramic-metal composite — tungsten + carbon sintered with cobalt binder. WC is far harder (90+ HRA vs 350 HV for pure W) and is the material cutting tools are made from.
What tooling should I use for tungsten heavy alloys?
For tungsten heavy-alloy milling starts, use coated carbide with positive rake geometry and a rigid setup. Through-tool coolant or strong evacuation is usually worth it. Expect much faster wear than steel and treat drilling or turning as separate workflows rather than reusing the milling assumptions from this chart.