Application of CNC Technology in Aerospace
This page is for design engineers and buyers who need flight-adjacent hardware cut from solid metal. It covers where CNC technology actually fits in aerospace work, which features need 5-axis, what tolerances hold on a real shop floor, and when milling is the wrong choice. Read it and you can judge whether a part belongs on a mill or somewhere else.
What CNC machining does in an aerospace build
Machined metal still carries brackets, housings, fittings and actuator bodies while composites and printed parts take the large skins.
Where CNC technology carries its weight
Aerospace assemblies are a mix of processes. Large skins and stringers go to composites. Engine housings and ducting go to casting or additive. The parts that must hold a bore, a flat face or a bolt pattern usually come off a CNC mill or lathe. That is the niche: dense, load-bearing geometry cut from a solid billet, where wall thickness and hole position decide whether the assembly closes up.
A machined bracket is expensive per kilo compared with a casting. It wins when the part count is low, the geometry is still changing, or the load path is too complex for a mold. Prototype and low-rate initial production are the classic cases. So are repair parts for older airframes, where no tooling exists anymore.
We see three recurring jobs. Structural fittings that join two load paths. Fluid and pneumatic manifolds with internal cross-drillings. And actuator or sensor housings where a seal face and a bearing bore must sit true to each other. Each one has a different failure mode, so each one needs a different setup plan.
- 1Fittings and clevisesLoad path through lugs and bores; position tolerance matters more than finish.
- 2ManifoldsCross-drilled passages; burr control and internal inspection are the hard part.
- 3HousingsBore-to-face alignment; usually a single-setup 5-axis part.
Picking the axis count for the part
Three-axis milling still handles plenty of aerospace parts: flat plates, shims, simple covers, drilled flanges. If every feature is reachable from one direction and the tolerance is looser than ±0.02 mm, a 3-axis job is cheaper and faster. Do not put a plate on a 5-axis machine just because the shop has one.
Four-axis work starts when the part has features on multiple faces but no compound angles. A rotary table lets the operator index to a second or third face without re-fixturing. That removes one source of positional error. It also cuts setup time, which matters on small batches.
Simultaneous 5-axis is for contoured surfaces and compound holes. A trunnion-style machine tilts the tool and the part together, so a hole that points 30° off vertical gets drilled in one pass. The real gain is not speed. It is keeping a bore and a face machined in the same setup, which holds their relationship tight. Re-fixturing a part usually adds 0.01–0.03 mm of error before the tool even touches it.
- 13-axisSingle-direction features, flat parts, ±0.02 mm or looser.
- 24-axisMulti-face parts without compound angles; fewer setups.
- 35-axis simultaneousContours, compound holes, bore-face alignment in one setup.
Machine and tolerance reference
Numbers below reflect the equipment and inspection we run on aerospace work.
| Parameter | Value | Notes |
|---|---|---|
| Tolerance | ±0.005 mm (±0.0002 in) | Achievable on critical features, not every dimension |
| Fine finish | Ra 0.2–0.8 μm | Requires extra pass and clean setup |
| Standard finish | Ra 0.8–1.6 μm | Default for most mating faces |
| As-machined | Ra 1.6–3.2 μm | Non-critical surfaces |
| Max part size | 4,000 mm | On the large gantry travel |
| 5-axis centers | 16 simultaneous | Trunnion and gantry types |
| 4-axis mills | 12 | Indexed rotary work |
| Rotary table | Ø400 mm | For round and indexed parts |
Alloys, and what each one does to the cut
Aluminum is the default for brackets and housings. 7075 machines clean and holds a good finish, but it is less corrosion-resistant than 6061 and costs more. 6061-T6 is the workhorse: weldable, stable, easy to anodize. 2024 is stronger in fatigue but gummy on the cutter and needs care with chip evacuation. For thin ribs, 7075 gives more stiffness per gram, which is why it shows up in control surfaces and internal frames.
Titanium is where the process gets slow. Ti-6Al-4V (TC4) conducts heat poorly, so the cutting edge takes the thermal load. Tool life drops, spindle speed drops, and the part can move as residual stress releases. Rough, stress-relieve, then finish. If a titanium part has thin walls, expect to leave 0.5–1 mm of stock for a separate finishing pass after the part has settled.
Stainless and nickel alloys turn up in high-temperature areas. 17-4PH (SUS630) gives good strength after heat treatment and machines better than Inconel. Inconel is reserved for hot sections; it work-hardens fast, so the tool must stay in cut and never rub. We keep feeds high enough to cut under the hardened layer rather than skimming it.
- 16061-T6General brackets and housings; easy to anodize.
- 27075High-stiffness ribs; better strength-to-weight, lower corrosion resistance.
- 3Ti-6Al-4VSlow speeds, heat at the edge, stress relief between ops.
- 417-4PHStrong after aging; predictable chips, good for fittings.
When CNC is the wrong answer
If the part is hollow with large internal volume, a machined billet wastes 70–90% of the stock as chips. Casting or additive wins on material and time. The crossover is usually around a few hundred parts per year, but geometry matters more than volume. A complex internal lattice is not a milling job at any quantity.
Very large thin panels are a poor fit too. A 3 m skin with 1.5 mm walls will deflect under clamping and chatter during the cut. Sheet metal or a composite layup holds the shape better. Machining can still trim the edge and drill the fastener holes.
Tight flatness over a long span is another flag. A 500 mm plate ground flat to 0.02 mm will move after machining unless the stock is stress-relieved first. If the drawing demands flatness that the raw plate cannot hold, talk to us before the order. Releasing stress is a process step, not a machining step, and it changes the price.
- 1High hollow volumeCasting or additive saves material and cycle time.
- 2Large thin panelsClamping and chatter risk; sheet or composite is better.
- 3Long flatness specsNeeds stress-relieved stock and a defined process sequence.
Inspection and traceability worth paying for
Aerospace buyers care less about the machine list and more about what happens after the cut. We check incoming stock, monitor dimensions in process, and inspect 100% of parts before shipment. Reports go out on request. That covers first article and production runs without a separate inspection contract.
The tolerance on the drawing should match the tolerance on the inspection report. If a bore is called at ±0.005 mm, the CMM plan has to sample it at enough points to catch lobing, not just measure two diameters. We agree the inspection method with the customer before the first cut on critical features.
Documentation runs alongside the part. Material certificates, plating certificates and inspection records stay linked to the lot. Our quality system is certified to ISO 9001:2015, IATF 16949:2016, ISO 13485:2016 and ISO 27001:2022. Uploads and drawings stay confidential, and an NDA is available on request.
- 1IncomingStock checked against certificate before machining.
- 2In-processDimensions monitored during the run, not only at the end.
- 3Final100% inspection; reports issued on request.
Common questions from aerospace engineers
What tolerance can you actually hold on a titanium aerospace part?
On critical features, ±0.005 mm is achievable when the setup is planned for it. That means roughing, stress relief, then finishing, with the finishing cut taking light passes.
Not every dimension on the drawing needs that number. Holding ±0.005 mm across a whole part drives cost up fast. Mark the two or three dimensions that matter and leave the rest at a general tolerance.
Do you machine Inconel and other high-temperature alloys?
Yes. Inconel and similar nickel alloys are in our material range, alongside titanium TA1, TA2 and TC4 (Ti-6Al-4V).
These alloys cut slowly and wear tools, so cycle time and price reflect that. Send the geometry and we will tell you if a different alloy would do the same job for less.
How do you handle thin walls that distort during machining?
The usual sequence is to remove most of the material while the part is still stiff, then relieve stress, then take the final passes with light depths of cut and support from soft jaws or a fixture.
If the wall is under 1 mm, we may ask for a small design change such as a temporary rib that gets cut away at the end.
Can you machine a part that is larger than your standard travel?
Our largest travel is 4,000 × 400 × 150 mm, with medium travels of 750 × 1,150 × 550 mm and 600 × 600 × 600 mm. If a part exceeds the envelope, we can split the design or discuss an alternative process.
Tell us the envelope at the quote stage so we can flag it before tooling or fixtures are made.
What finishes are available for aerospace housings and fittings?
Anodizing in clear, color, hardcoat and conductive types, plus electroless nickel, zinc, silver and gold plating. Powder coating, black oxide, bead blasting, tumbling, brushing and polishing are also available.
Laser marking needs a minimum character height of 1.5 mm. For conductive anodize on a grounded housing, note the masking areas on the drawing.
How do you keep drawings and models confidential?
Uploads are secure and confidential, and we sign an NDA on request before files are shared.
Our information security management system is certified to ISO 27001:2022, which covers how files, access and records are controlled.
Send the drawing, get a process answer
Upload your model and we will come back with a quotation and a free DFM analysis within 12 hours, including notes on setup, material and any feature that will not cut cleanly.
12-hour quoteFree DFM analysis100% inspectionNDA on request
