Aerospace CNC Alloy Machining Services

The alloy choice drives everything downstream: tool path, spindle speed, fixture stiffness, inspection method and lead time. A bracket that flies inside a cabin and a bracket bolted near an engine exhaust look similar on a print but behave nothing alike in the cut. Start with the service temperature, the load path and the weight target. Those three answers narrow the list fast.

Aluminum 7075-T6 gives high strength at low weight. It machines quickly and holds tight tolerances, which makes it the default for structural brackets, housings and prototype frames. It loses stiffness above roughly 120 °C, so keep it away from hot sections. 6061-T6 is weaker but welds and anodizes predictably, and it is cheaper per kilogram.

Titanium Ti-6Al-4V (TC4) carries about twice the strength of 7075 at similar density and keeps it to higher temperatures. The trade is machinability. Titanium conducts heat poorly, so heat stays in the cutting zone instead of leaving with the chip. That shortens tool life and can smear the surface if feeds are too light.

Inconel and other nickel superalloys hold strength at temperatures where aluminum and titanium have already given up. They work-harden almost instantly, so a tool that rubs instead of cuts will destroy the surface and the cutter together. These alloys are for exhaust-side parts, fasteners and hot structures. If your part does not see real heat, a superalloy is usually the wrong answer.

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  Strength-to-weight first7075-T6 for stiff, light structures below 120 °C.
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  Heat decides superalloysOnly specify Inconel if the part runs hot.
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  Corrosion and contact17-4PH and 316L where moisture or galvanic pairs matter.
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  Cost per part, not per kiloHard alloys raise tool cost and cycle time, not just material price.

Titanium is the alloy that catches most first-time buyers. It has low thermal conductivity, so the heat generated at the edge has nowhere to go except into the tool and the part. We run sharp, uncoated or lightly coated carbide, climb milling, and heavy enough feed to keep the edge cutting rather than rubbing. Coolant goes under high pressure straight at the contact zone. Light finishing passes on titanium are a trap: they polish the surface while work-hardening a skin just under it.

Nickel superalloys work-harden even faster. Inconel 718 can harden to the point where the next pass cannot cut the layer the last pass left behind. The fix is rigidity. Short tool holders, minimal overhang, and a machine that does not flex under load. We hold these parts on 5-axis centers because every extra setup adds a chance to lose position on a material that is already hard to re-cut.

Aluminum is the easy one, with two exceptions. Thin walls deflect under cutting force, so wall thickness below about 0.8 mm needs light radial engagement and support from both sides. Deep pockets trap chips, and a recut chip will mark a finished floor. Through-spindle coolant and a programmed chip-evacuation path solve most of it.

Stainless 17-4PH sits in the middle. In the H900 condition it machines cleanly and takes a good finish, but it work-hardens if the tool dwells. 316L is gummier and tends to tear rather than shear, so we slow the surface speed and keep the feed up. Both are common on fittings, brackets and actuator housings where corrosion resistance is the point.

Tolerance is not a property of the machine alone. A 5-axis center that holds ±0.005 mm on aluminum will not automatically hold it on Inconel. The difference comes from thermal growth, tool deflection and how many times the part is re-fixtured. Every setup adds stack-up error. On hard alloys we plan the operations so critical features come off in one setup wherever the geometry allows.

Thermal control matters more than most drawings suggest. Titanium and superalloys both pull heat into the workpiece, so a part can grow several micrometres during a long cut and shrink back after it cools. We rough, let the part stabilize, then finish. Measuring a hot part and adjusting the offset is how good bores go out of round.

Inspection follows the same logic. Raw material certificates are checked against the alloy grade before the first chip. In-process checks catch drift on long runs. Final inspection is 100% before shipment, with reports on request. For flight hardware, the material certificate and the inspection record travel with the part.

We run 127 high-precision CNC machines across three plants, including 16 simultaneous 5-axis centers and 16 mill-turn centers. Maximum processing size is 4,000 mm, which covers long structural members that will not fit a standard VMC envelope. The Ø400 mm rotary table handles round features that would otherwise need a separate setup.

Surface finish on aerospace alloy parts usually serves a function, not an appearance. Anodizing on aluminum adds wear resistance and a dielectric layer; hardcoat is thicker and more abrasion-resistant but changes dimensions, so we mask or compensate. Titanium and stainless often go out as machined with bead blasting to remove tool marks and reduce the chance of fatigue cracks starting at a scratch.

As-machined finish lands around Ra 1.6–3.2 μm on most alloys. A high finish of Ra 0.8–1.6 μm is routine on sealing faces, and fine finishing to Ra 0.2–0.8 μm is available where a print calls for it. Tighter finish costs cycle time, so do not specify it on a face no one touches.

Some geometry is not worth machining. Long thin tubes, large flat panels and parts with many identical holes are often cheaper as sheet metal or as a casting with machined interfaces. We machine the critical bores and faces and leave the rest to the process that fits. That is a routing decision, not a compromise.

Threads, slots and thin ribs need a second look on hard alloys. A thread that is fine on 6061 may strip or chip on Inconel. We adjust thread form, add a relief groove, or move to a larger pitch when the design allows. If a feature cannot be cut reliably, we say so before the run, not after.

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  Anodize adds thicknessHardcoat can shift a bore by tens of micrometres. Mask or compensate.
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  Bead blast before anodizeRemoves tool marks and gives a uniform base.
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  Do not over-specify finishRa 0.2–0.8 μm only where a seal or bearing needs it.
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  Mixed routing is normalCast or formed body, machined interfaces.

Aerospace alloy work rarely arrives as a single quantity. A program often starts with one or two prototypes for fit checks, moves to a small batch for test articles, then settles into a steady run. We quote all three stages the same way: no minimum order quantity, from one prototype to 10,000+ part runs.

The first stage is where DFM pays off. We return a quotation and a free DFM analysis within 12 hours, flagging features that will be slow, fragile or expensive on the alloy you chose. Moving a corner radius or relaxing a tolerance at that point costs nothing. Finding the same problem after tooling is cut costs weeks.

Once the drawing is fixed, production can start within 24 hours and parts ship in 3–5 days. For repeat programs we keep the fixture, the tool list and the inspection plan on file, so the second run does not repeat the first run's learning curve. Historical late-delivery probability is below 2%.

Confidentiality is handled up front. Uploads are secure and confidential, and we sign an NDA on request before drawings change hands. Aerospace prints carry controlled data, so this is usually the first document exchanged, not the last.