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Aluminum and titanium sit at opposite ends of the machining spectrum. Aluminum rewards high spindle speeds, sharp tools, and aggressive material removal rates; titanium punishes exactly the same approach with work hardening, heat buildup, and rapid tool wear. That is why a shop that produces excellent aluminum parts can still scrap your Ti-6Al-4V order, and vice versa. Choosing a cnc machining supplier for these two materials means verifying that the shop has genuinely mastered both process windows, not just one. This guide walks through the criteria that actually predict success, the red flags worth walking away from, and the questions to ask before you release a purchase order.
Before evaluating any supplier, it helps to understand what each material does to a machine shop, because the answers you listen for are different.
Aluminum alloys such as 6061-T6 and 7075-T6 cut freely, but quality failures show up in the details: burrs on thin walls, built-up edge on tools that leaves a smeared finish, dimensional drift on large plates, and scratches that only become visible after anodizing. A capable aluminum shop runs high-speed spindles, controls chip evacuation carefully, and understands how much material anodizing adds or removes on a critical dimension.
Titanium alloys, especially Ti-6Al-4V, are a different discipline entirely. Titanium conducts heat poorly, so cutting heat concentrates at the tool edge instead of leaving with the chip. It also work hardens: a dull tool or a timid cut glazes the surface and makes the next pass harder than the material underneath. Good titanium cnc machining depends on rigid machines, sharp coated tools, high-pressure coolant, lower cutting speeds with steady feed rates, and programmers who never let a tool dwell or rub. When you interview a supplier, you are really asking whether they respect these constraints.
"We machine aluminum and titanium" is a marketing line. What you want is evidence with your specific grade and part geometry. Ask for photos, inspection reports, or case studies of similar parts. A supplier working regularly with 6061-T6, 7075-T6, and Ti-6Al-4V will answer immediately; a generalist will talk in circles. Relevant industry experience matters too, because a medical or aerospace shop already lives with the traceability and documentation those alloys usually require.
The machine list tells you more than the sales pitch. For aluminum, look for high-speed machining centers and enough 3-axis, 4-axis, and 5-axis capacity to finish parts in as few setups as possible. For titanium, rigidity and torque matter more than speed, and multi-axis machines reduce the number of times a hard, expensive workpiece is re-fixtured. Complementary processes count as well: CNC turning for shafts and threaded parts, surface grinding for critical flatness, and wire EDM for hardened or heat-sensitive features that milling cannot reach cleanly.
Every shop website claims tight tolerances. The credible ones state a number and then prove it with metrology. A claim such as ±0.002 mm is only meaningful if the supplier verifies parts with coordinate measuring machines, gauges threads properly, and ships dimensional reports with the order. An ISO 9001:2015 certified quality system is the baseline that makes those reports trustworthy, because it forces documented processes rather than heroic individual effort. Ask what a typical inspection report looks like before you order.
Finishing is where aluminum and titanium parts most often go wrong at the last step. Type II and Type III anodizing change dimensions, so a supplier who machines aluminum well will compensate for coating thickness in the CAM stage and measure parts before and after plating. Titanium parts typically need passivation, polishing, or blasting handled with equal care. A shop with in-house or tightly managed aluminum cnc machining and finishing under one roof owns the result end to end, instead of blaming the plating vendor when threads seize or dimensions drift.
The quoting stage is a free audition. A strong supplier reads your drawing and comes back with specific design-for-manufacturing suggestions: a wall thickness that will chatter in titanium, a corner radius that forces a slow tool, a tolerance that is tighter than the function needs and doubles the cost. Generic feedback like "looks good, we can make it" tells you nothing. Detailed, part-specific feedback tells you engineers, not just salespeople, looked at your files.
Many projects start as a handful of prototypes and grow into repeat production. Confirm that the supplier handles both without re-quoting from scratch or changing processes mid-stream. Consistent tooling, fixturing, and inspection methods between the prototype and production lots are what keep revision B identical to revision A.
The quality of the answers matters more than the speed of the quote. Suppliers who answer with specifics have solved these problems before; suppliers who answer with reassurance have not.
As a practical benchmark, ANOK Precision Manufacturing in Shenzhen, China, illustrates what a dual-material shop looks like. The company has machined custom parts since 2007, holds ISO 9001:2015 certification, and works daily with aluminum grades such as 6061-T6, 7075-T6, and 6082 alongside difficult materials including Ti-6Al-4V titanium, Inconel, and PEEK. Its shop floor combines 4-axis and 5-axis machining centers, nearly 15 CNC turning machines, precision surface grinding, and wire EDM, holding tolerances down to ±0.002 mm and surface finishes to Ra 0.2. In-house anodizing and surface treatment keep finishing dimensions under control, and DFM feedback is part of the standard quoting process for medical, aerospace, and automation customers.
Whether you choose ANOK or another partner, run every candidate through the same filter: material-specific evidence, suitable equipment, verified tolerances, controlled finishing, and engineering-grade communication. Aluminum forgives sloppy process choices for a while, and titanium never does. A supplier who respects both materials on those terms is a supplier you can keep.