An aerospace startup in Canada ordered 30 titanium brackets from a shop that advertised titanium CNC machining on its homepage. The parts arrived on time, the dimensions matched, and the team celebrated. During the environmental test, two brackets cracked at the bolt hole. The shop had machined Grade 5 from bar stock without a mill test report, skipped stress relief, and used a general-purpose coolant that left chlorine residue on the surface. The engineer had compared price per kilogram, not process control. Before you release the PO, run the six checks below.
Material Grade and Mill Test Report
Start with the bar stock, not the brochure. Titanium CNC machining shops that buy cheap bar from a commodity trader will ship parts with inconsistent chemistry. Ask for the grade (Grade 2 commercially pure, Grade 5 Ti-6Al-4V, Grade 23 Ti-6Al-4V ELI), the standard (AMS 4928, ASTM B348, or ASTM F136 for medical), and the mill test report for the exact batch. A medical device company in Sweden once received Grade 5 parts that failed the biocompatibility test; the shop had used Grade 2 bar and relabeled it. Rule of thumb: only work with a titanium cnc machining shop that can show you the MTR for the heat lot your parts came from, and cross-check the heat number on the part itself.
Tooling and High Pressure Coolant
Titanium cuts hot. A shop that machines aluminum all day will burn titanium inserts within minutes. Ask whether the shop uses solid carbide or coated carbide tools, whether they run high-pressure coolant at 70 bar or higher, and how they handle chips. Titanium chips are thin, hot, and can self-ignite if they pile up. A pump manufacturer in Italy once received titanium housings with built-up edge on the sealing face; the shop had run the same feed rate they use for steel. Ask titanium cnc machining shops for their cutting parameters, tool life per part, and chip management protocol on the floor. A shop that runs titanium on a 3-axis knee mill is not a titanium cnc machining shop; it is a shop that hopes the job does not break a tool. Ask what spindle power they run, whether the machine enclosure is sealed against titanium dust, and how often they change inserts on a typical Grade 5 bracket.
Tolerance and CMM Inspection
Tight tolerances on titanium are harder than on aluminum because the material spring-backs. A shop that holds ±0.02 mm on aluminum may only hold ±0.05 mm on titanium. Ask for the CMM report on a similar part, not just a quote. A drone maker in the Netherlands ordered 20 titanium brackets; the first batch failed the fit check because the shop had used a general tolerance callout. Ask titanium cnc machining shops for a first article inspection report with every critical dimension, and confirm the CMM calibration is current.
Stress Relief and Passivation
As-machined titanium holds internal stress. Parts machined without stress relief will warp weeks after delivery. A structural component supplier in Germany shipped titanium brackets to a customer; two months later, the parts had shifted by 0.3 mm and would not fit the assembly. Ask whether the shop runs stress relief annealing after roughing, and whether they acid pickle or passivate the parts. For medical and marine parts, passivation removes iron contamination that would otherwise cause pitting corrosion. A titanium cnc machining shop that skips these steps is a job shop, not a supplier. Also ask whether they control hydrogen pick-up during pickling; titanium absorbs hydrogen in acid baths and can become brittle, which is a hidden failure that shows up months after delivery.
Certifications for Aerospace and Medical
Certifications decide whether the part can enter regulated industries. ISO 9001 is the minimum. AS9100 is required for aerospace. ISO 13485 and ASTM F136 are required for medical implants. A defense contractor in Australia once sourced titanium parts from a shop without AS9100; the parts passed lab tests but were rejected at the customer quality audit. Ask for the certification numbers and verify them on the registrar website. Also ask whether the titanium cnc machining shop has experience with NADCAP special processes if your program requires it.
Clean Packaging and Lot Traceability
Titanium scratches easily, and contamination from other metals on the same shipping pallet causes rust spots. A medical startup in Brazil received titanium parts with visible iron stains on the surface; the shop had shipped them in the same box as steel parts. Ask titanium cnc machining shops whether parts are individually wrapped, whether the packaging is clean-room grade for medical, and whether each part carries a heat lot number. Also ask whether they can provide a full traceability file: MTR, FAI, CMM report, passivation certificate, and packaging record, bundled with the shipment.
Run these six checks and the titanium cnc machining shop you pick will ship parts with traceable material, sharp tooling, stress relief that holds, and a quality file your customer audit will accept. For related background, read our precision machining services article and our cam driven indexer article before you shortlist; when the quotes come back, cross-check the gearbox precision in our strain wave gearing article and the motion control angle in our servo motor drive article, so the 30 titanium brackets do not turn into an environmental test failure. Ask for two sample parts before you commit to a batch of 50, have them tested by your own lab, and only then release the PO; that 2-week sample cycle saves you a 3-month rework later. A serious titanium cnc machining shop will welcome the sample test, not dodge it on the phone.