Titanium is unrivalled where lightness and corrosion resistance are required together: implants and surgical instruments, aircraft structural parts, chemical plant fittings, seawater pumps, high-performance bicycle and engine parts. In machining, however, it heads the class of "difficult materials". This article, a continuation of our stainless steel and aluminium articles, covers the practical aspects of titanium for buyers and designers.
Grade 2 and Grade 5: Properties
| Property | Grade 2 (commercially pure, 3.7035) | Grade 5 (Ti-6Al-4V, 3.7165) |
|---|---|---|
| Composition | 99%+ Ti, low O/Fe | 6% Al, 4% V |
| Tensile strength | 345–480 MPa | 895–1,000 MPa (annealed) |
| Density | 4.51 g/cm³ | 4.43 g/cm³ |
| Corrosion resistance | Excellent (chlorides, seawater, oxidising acids) | Very good |
| Hardness | ~145 HB | ~330 HB |
| Weldability | Very good | Good (shielding gas mandatory) |
| Machinability (C45 = 100) | ~35–40 | ~20–25 |
| Typical use | Chemical, marine, heat exchangers, medical (Grade 2/4) | Aerospace, implants (ELI type Grade 23), motorsport |
| Standard | ASTM B348, DIN 17862 | ASTM B348, AMS 4928 |
In medical implants, the lower-oxygen Grade 23 (Ti-6Al-4V ELI) is used instead of Grade 5; Grade 2 and Grade 4 are common in surgical instruments. Documentation requirements are explained in our medical device parts article.
Why Titanium Is Hard to Machine
- Low thermal conductivity: Cutting heat is not carried away with the chip; it accumulates at the cutting edge and tool life shortens.
- Chemical reactivity: At high temperature it reacts with the tool material, causing built-up edge (BUE) and crater wear.
- Low modulus of elasticity: Half that of steel; thin-walled parts deflect under cutting force, creating vibration and dimensional deviation.
- High strength-to-weight and work hardening: Cutting forces are high; repeated rubbing of the surface causes hardening.
- Flammability: Fine chips and dust can ignite; coolant and chip management are a safety issue.
Cutting Parameters and Tool Selection
- Cutting speed: 60–90 m/min for Grade 2, 40–70 m/min for Grade 5 (uncoated or PVD-coated carbide). Far below steel (200–300 m/min).
- Feed and depth of cut: Medium-to-high feed, constant depth of cut; low feed increases work hardening.
- Tooling: Fine-grain carbide, sharp positive cutting geometry, high helix; PVD TiAlN or AlCrN coating. In milling, high-efficiency machining (HEM/trochoidal) is the standard strategy.
- Rigidity: Short tool length, strong clamping, an approach that prevents chatter.
- Chip control: Long, tough chips; chip-breaker geometry and high-pressure coolant in turning.
Coolant
Abundant, high-pressure (70+ bar) coolant is critical for both tool life and safety; dry machining is not recommended for titanium. High-pressure coolant breaks the chip and removes heat; oil coolant is common in Swiss-type turning. Chips are collected and stored separately; titanium swarf is valuable for recycling but must be kept dry and separate because of the fire risk.
Tolerance and Surface Finish
Tolerances of ±0.01–0.02 mm are achievable in titanium, but deflection in thin walls and thermal expansion must be taken into account. Ra 0.8 µm is routine in turning; Ra 0.4 µm is possible with careful parameters. Titanium is prone to grinding damage (burning, cracking); where possible, precision turning is preferred over grinding. Edge breaking and deburring require care; in medical parts electropolishing or anodising (coloured titanium anodisation) is applied.
Material Supply and Certificates
Titanium is not produced domestically in Turkey; bar and plate are imported from Europe, the USA or Asia. Stock may be available in standard diameters (Ø10–100 mm Grade 5, Grade 2); special sizes take 4–10 weeks. The price is 15–30 times that of steel and 8–15 times that of 6082 aluminium, and volatile. Certificate: a 3.1 certificate containing chemical analysis and mechanical testing to the ASTM B348 or AMS specification; in medical and aerospace, the melt lot number and traceability are mandatory. In critical projects, the customer supplying the material from its own approved source (free-issue) is a common and recommended route.
Price Structure
About 30–50% of a titanium part's price is material and 40–60% is machining time and tooling cost. A part of the same geometry can be 4–8 times more expensive than steel and 6–12 times more than aluminium. The biggest saving a designer can make is to reduce the chip ratio: near-bar geometry, forged/pre-shaped blanks, or additive manufacturing + finish machining. There are further suggestions in our DFM article.
Buying Titanium Parts from a Contract Supplier
- Ask concretely about titanium experience: which grades, which parts, how much per year?
- Is high-pressure coolant and suitable tooling infrastructure in place?
- What is the material source and certificate chain? Is free-issue accepted?
- How are chip management and material segregation (no mixing with steel) ensured?
- Request an inspection report and surface measurement with the sample; in titanium, first-part performance determines the series.
TORNELLE's main materials are steel, stainless, aluminium and brass; we evaluate titanium projects case by case in terms of geometry, quantity and material supply, and say so clearly for jobs that are not a good fit.
Titanium Notes for Designers
- Do not go below 1.5 mm wall thickness; deflection and vibration spoil dimensions.
- Keep corner radii large; sharp internal corners are a problem for both tooling and fatigue life.
- In threads, 60–70% thread engagement is sufficient instead of full depth; tapping is risky in titanium, thread milling is preferred.
- Keep the hole length-to-diameter ratio below 5:1; heat and chips cause problems in deep holes.
- Surface markings: state which surfaces are functional and which are visual; unnecessary Ra 0.4 doubles the cost.
- Discuss alternative materials: many "titanium" parts also work in 1.4404 or 7075.
Coatings and Finishing Operations
Titanium's own oxide layer provides corrosion resistance; an additional coating is usually not needed. Coloured anodising (Type II/III) is common in medical parts for identification and aesthetics; for hardness, nitriding or DLC coating can be applied. Passivation and cleaning are subject to validation in medical parts; ask the supplier who performs these processes and which documents are provided.
Frequently Asked Questions
Should I choose Grade 2 or Grade 5?
Grade 2 if corrosion resistance is the priority and the load is low; Grade 5 if high strength is needed. Grade 2 is easier to machine and cheaper.
Why are titanium parts so expensive?
Material is 15–30 times steel, machining time 3–5 times; tool wear is high. A 4–8-fold price difference overall is normal.
Can titanium be machined on a Swiss-type lathe?
Yes; medical screws and small implant components are produced on Swiss-type lathes. Oil coolant and special tooling are required.
Can I use stainless steel instead of titanium?
If weight is not critical and chloride corrosion is not extreme, 1.4404 or duplex stainless is sufficient in most applications and far more economical.
Conclusion
Titanium is a material that can be machined reliably with the right parameters, coolant and material chain, but it is not routine work for every shop; concrete experience and infrastructure must be asked about when selecting a supplier. To assess whether your part makes more sense in titanium or stainless, send the drawing via our quote form; we respond with an alternative material recommendation.
