Titanium Swiss Machining: Grade 2, Grade 5 (Ti-6Al-4V) and Grade 23

Titanium is not especially hard, but its thermal conductivity is roughly 1/7th that of aluminum and a fraction of steel's, so the heat generated at the cutting zone cannot escape through the part or the chip the way it does in other metals. It concentrates at the tool edge. Combine that with titanium's tendency to keep its strength at elevated temperature and its chemical reactivity with tool materials, and you get rapid tool wear, edge cratering, and the risk of welding chips to the insert. The response is counterintuitive: run slow. Ti-6Al-4V on a Swiss lathe is typically cut at 100 to 200 SFM with sharp carbide, far below what the part diameter would suggest, with heavy, copious high-pressure coolant aimed directly at the edge to pull heat away. Feed has to be steady and the tool must never dwell, because a stationary hot edge will work-harden the surface and abrade. Sharp, positive-rake, polished inserts in fine-grain carbide are standard, and tool life is managed conservatively because a worn edge generates even more heat in a self-accelerating cycle.

Grade 2 is commercially pure titanium: softer, more ductile, excellent corrosion resistance, and used where strength is secondary to corrosion performance, such as chemical, marine, and some medical hardware. It is gummier to cut than the alloyed grades and produces stringy chips, so chip control is the main challenge, but tool wear is lower than with Grade 5. Grade 5, Ti-6Al-4V, is the workhorse alloy: roughly 130 ksi yield strength, the default for aerospace fasteners and structural fittings and for many medical implants. Grade 23 is Ti-6Al-4V ELI (extra-low interstitial), a higher-purity version with lower oxygen and iron that gives better fracture toughness and ductility, which is why it is the implant grade of choice for orthopedic and trauma devices. Grades 5 and 23 machine almost identically from the operator's seat; the difference is in the certified chemistry and the documentation trail, not the cutting behavior. For medical work the ELI grade plus full traceability is usually non-negotiable.

Fine titanium chips and dust are flammable and, once ignited, burn intensely and cannot be extinguished with water, which can actually accelerate the reaction. Swiss shops running titanium maintain disciplined chip management: frequent clearing of the chip conveyor and pan, separation of titanium swarf from other metals, dedicated chip bins, and Class D fire suppression on hand. High-pressure flood coolant is as much a fire-prevention measure as a cutting aid because it keeps chip temperature down and clears swarf before it accumulates. Fixturing leans on the Swiss machine's core strength: the guide bushing supports the bar right at the cut, which is critical because titanium's lower modulus of elasticity (about half that of steel) makes parts more prone to deflect and spring back. That low modulus means the part flexes under cutting force and recovers afterward, so light finishing passes and rigid support are essential to hit tolerance. Long slender titanium parts that would chatter or taper on a conventional lathe are exactly where Swiss machining earns its keep.

Medical implants dominate. Bone screws, dental abutments, spinal hardware, and trauma fasteners are overwhelmingly Grade 23 ELI, turned on Swiss machines under ISO 13485 with full lot traceability, because the parts are small, threaded, slender, and biocompatibility plus strength-to-weight are paramount. The combination of tight concentricity, fine threads, and a fully documented material trail is squarely in Swiss machining's wheelhouse. Aerospace and defense pull Ti-6Al-4V for fasteners, hydraulic fittings, and structural pins where the strength-to-weight ratio justifies the material and machining cost, frequently under AS9100 and ITAR control. Energy and chemical applications use Grade 2 for corrosion-critical small components. Across all of these, titanium is never the cheap option; it is chosen when the application genuinely needs the corrosion resistance, biocompatibility, or strength-to-weight, and the buyer accepts the slower cycles and higher material cost that come with it.