Titanium Machining Guide
Why titanium destroys cutting tools, and what actually works when you run it — speeds, feeds, tooling, coolant, tapping, and the fire risk that most guides leave out. Written from running Ti-6Al-4V regularly, not from a datasheet.
Why Titanium Is Hard: Three Reasons That Compound
Titanium isn't "hard" in the sense that hardened steel is hard — Ti-6Al-4V is around 36 HRC, which isn't extreme. The difficulty comes from three properties stacking on top of each other.
1. It barely conducts heat
Ti-6Al-4V has a thermal conductivity of about 6.7 W/m·K. Aluminium is around 167 — roughly twenty-five times higher. Steel is around 16–50 depending on the grade.
What this means at the cutting edge: in aluminium, most of the heat generated by cutting leaves with the chip. In titanium, it can't. It stays concentrated in a tiny area at the tool tip, where temperatures can pass 1,000°C. That's what kills cutting tools — not hardness, but heat with nowhere to go.
2. It's chemically reactive at cutting temperature
At those temperatures, titanium has a strong affinity for the materials in cutting tools. It diffuses into the tool surface and can micro-weld itself to the edge, then tear fragments out as the chip flows past. This is why tool life in titanium is measured in minutes, not hours, if you get the parameters wrong.
3. Low elastic modulus makes it deflect
Titanium's elastic modulus is about 113.8 GPa — roughly 60% of steel and lower than you'd expect for a metal this strong. Under cutting pressure the workpiece springs away from the tool, then springs back.
The consequence: the tool rubs instead of shearing. Rubbing generates heat without removing material, and it work-hardens the surface for the next pass. Combined with reason 1, you now have a hotter tool cutting a harder surface. That's the downward spiral.
The Rule That Matters Most: Never Let It Rub
If you take one thing from this page: in titanium, rubbing is failure. The moment a tool stops cutting and starts rubbing, it work-hardens the surface it just touched, and the next pass is cutting through a harder layer with a hotter tool.
Practically, this means:
- Feed high enough to maintain chip load. A feed that's too light is worse than one that's slightly heavy. The tool edge must be engaged in cutting material, not skimming over it.
- Never stop feeding mid-cut. If the tool dwells in contact with the workpiece, you've hardened that spot. This is why climb milling with consistent engagement beats conventional milling in most titanium operations.
- Back the tool away before retracting — don't drag a spinning cutter back across a surface you just machined.
- Use sharp tools and change them early. A slightly worn tool rubs. In aluminium a worn tool still cuts; in titanium it's already making things worse.
Cutting Parameters: Titanium vs Everything Else
| Parameter | 6061 Aluminium | 304 Stainless | Ti-6Al-4V |
|---|---|---|---|
| Cutting speed (m/min, carbide) | 200–400+ | 60–120 | 30–60 |
| Thermal conductivity (W/m·K) | 167 | 16 | 6.7 |
| Elastic modulus (GPa) | 68.9 | 193 | 113.8 |
| Hardness | ~95 HRB | ~70 HRB | ~36 HRC |
| Relative cycle time | 1× | 3–5× | 5–10× |
| Coolant strategy | Flood or mist | Flood, high pressure helps | High-volume, high-pressure, aimed at the edge |
Note that titanium's hardness is unremarkable. It's the speed you're forced to run at — an order of magnitude below aluminium — plus the tool life that makes it expensive. For how that translates into cost, see how machining cost is calculated. Most of our titanium work is for aerospace components where Ti-6Al-4V's strength-to-weight wins.
Tool Selection
- Substrate: fine-grain tungsten carbide with a tough cobalt binder. Toughness matters more than hardness here because of the interrupted thermal cycling.
- Coating: TiAlN or AlTiN perform well. Avoid TiN — titanium's affinity for it makes matters worse rather than better.
- Avoid ceramics and PCD for titanium. Both react chemically at the temperatures involved.
- Geometry: sharp cutting edges with positive rake. A honed-but-sharp edge is the balance — a heavy hone promotes rubbing.
- Rigidity over everything. Short tool overhang, largest diameter the geometry allows, solid toolholding. Any deflection turns cutting into rubbing.
Coolant: Volume and Pressure, Aimed Correctly
Titanium needs a lot of coolant, delivered at pressure, aimed at the cutting edge — not poured over the workpiece. The job is to get heat out of the tool tip and to break the chip away from the edge before it welds.
High-pressure coolant through the tool (70 bar and up where the spindle allows it) makes a measurable difference to tool life, because it reaches the one place that matters and it clears chips from deep features.
Tapping and Drilling: Where Most Shops Struggle
Holes are where titanium causes the most grief, and it's the same two properties again.
Tapping: titanium is gummy at temperature, and the low modulus means the material springs back and closes in on the tap, gripping it. In a blind hole, chips pack and the tap seizes and snaps. What helps:
- Spiral-point taps for through holes, spiral-flute for blind holes — chip evacuation is everything
- Generous flute space and a tap designed for titanium
- Low speed, rigid synchronous tapping (no floating holder if you can avoid it)
- A tapping lubricant with extreme-pressure additives — not general-purpose cutting fluid
- Don't bottom out. Leave clearance.
Drilling: use a sharp drill with a wider point angle than you'd use in steel, peck to clear chips, and keep the feed constant. A drill that dwells in titanium will work-harden the hole bottom and the next peck pays for it.
The Fire Risk Nobody Mentions
This belongs in every titanium guide and is missing from most.
Fine titanium chips are pyrophoric — they can ignite spontaneously in air. A bin of dry titanium swarf is a genuine fire risk, and a titanium fire is not an ordinary fire:
- Never use water. Water can react with burning titanium and make it dramatically worse, including generating hydrogen.
- Standard ABC extinguishers are ineffective or dangerous on titanium fires.
- Class D dry powder extinguishers, or dry sand, or specialised metal-fire extinguishers — that's what's needed.
What a shop running titanium actually does: keep chips wet with coolant, collect them in sealed metal containers, never mix titanium swarf with steel or aluminium chips, and keep the workspace clear of combustible clutter. It's entirely manageable — the point is that it has to be planned for before the first chip is cut.
Which Grade?
| Grade | What it is | Use it for |
|---|---|---|
| Grade 2 (commercially pure) | Lower strength, excellent corrosion resistance, easier to machine than the alloys | Chemical processing, marine hardware, heat exchangers |
| Grade 5 (Ti-6Al-4V) | The workhorse — roughly half of all titanium used. 880 MPa yield, good all-round | Aerospace structures, motorsport, high-performance engineering |
| Grade 23 (Ti-6Al-4V ELI) | Extra-low interstitial version of Grade 5 — better ductility and fracture toughness | Medical implants, surgical instruments |
If a drawing says "titanium" without a grade, ask. Grade 2 and Grade 5 are not interchangeable — the strength difference is large and so is the cost. Our three-material comparison puts Grade 5 alongside aluminium and stainless on the numbers that decide.
When Not to Use Titanium
We turn down titanium work occasionally, and it's usually for one of these reasons:
- Weight isn't the constraint. If the part sits still and just needs strength, 17-4PH stainless gives you more absolute strength for a fraction of the cost.
- It's a bearing or sliding surface. Titanium galls badly and has poor sliding wear. A plain titanium bearing surface is usually a mistake without surface treatment.
- Service temperature above ~400°C. Titanium loses out to other alloys up there.
- The budget can't absorb 5–10× the machining time. Sometimes the honest answer is that the application doesn't need what titanium offers.
If any of those apply, we'll say so before quoting rather than after. Our page on cutting machining cost covers the levers if cost is the binding constraint.
Titanium Machining Questions
Why is titanium hard to machine?
What cutting speed should I use for Ti-6Al-4V?
Are titanium chips a fire hazard?
Why do taps break so often in titanium?
When should I not use titanium?
How much more does a titanium part cost than the same part in aluminium?
Send the Drawing and the Application
Tell us the grade, the application and what the part actually has to survive. If titanium is the right call we'll quote it properly — and if aluminium or stainless would do the job, we'll say that instead. For lightweight, non-structural parts, an engineering plastic is often the better answer — see our plastic machining guide.
Related: Material Selection Guide