CNC Machining Services for Aerospace: How to Choose and What to Verify
This guide is for engineers and purchasing teams evaluating CNC machining services for aerospace work. It covers tolerance capability, material stock, certification scope, lead time, and MOQ. By the end you can tell whether a shop fits your part or will burn your schedule.
In this article
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Key takeaways
What to compare across CNC machining services for aerospace
Use this as a scorecard when you shortlist two or three shops.
| Criterion | What good looks like | Red flag |
|---|---|---|
| Tolerance | ±0.005 mm (±0.0002 in) held in production | Only quotes best-case single-part numbers |
| Surface finish | Ra 0.8–1.6 μm as standard, Ra 0.2–0.8 μm on request | Cannot state a Ra range |
| Material stock | Aluminium, stainless, titanium, Inconel on hand | Orders every grade per job |
| 5-axis capacity | 16 simultaneous 5-axis centers | Three-axis only, manual repositioning |
| Max part size | 4,000 mm maximum processing size | Cannot state travel envelope |
| Certifications | ISO 9001:2015, IATF 16949:2016, ISO 13485, ISO 27001 | Says aerospace grade, no scope |
| MOQ | No minimum order quantity | High minimum for prototypes |
| Quote turnaround | 12 hours with free DFM analysis | Weeks of silence after upload |
Tolerance, geometry, and when five-axis actually matters
Aerospace parts are judged on what the drawing says, not on what the machine can theoretically do. Ask a shop to hold ±0.005 mm (±0.0002 in) and you are asking about thermal drift, tool wear, and fixturing stiffness. The number only means something when it holds across a lot of 50 or 500, not on a single polished sample.
The geometry decides the machine. Flat plates with drilled holes run fine on three-axis mills. Once you add curved airfoils, internal cooling channels, or intersecting angled holes, three-axis machining needs multiple setups and each setup adds stack-up error. Five-axis centers cut those features in one setup, so the datum stays the same from first cut to last.
That said, five-axis is not automatically better. A simple bracket with one critical bore may run faster and cheaper on a three-axis machine with a good fixture. The honest question is how many setups the part needs and how much error each setup adds.
- 1One setup, one datumFive-axis keeps position error from accumulating across re-clamping.
- 2Reach mattersDeep pockets and undercuts need tool clearance check, not just axis count.
- 3Thin walls moveLightweight structures deflect under cutting force. Plan roughing and finishing passes.
Material selection for aerospace CNC machining services
Aluminium covers most brackets, housings, and mounting plates. 6061-T6 and 7075 are the common choices: 6061 machines cleanly and welds well, 7075 gives higher strength where weight is tight. 2024 and 5052 show up in sheet and skin work. The grade you pick changes cutting parameters, so state it on the drawing.
Stainless and titanium appear where temperature or corrosion rules out aluminium. 17-4PH (SUS630) holds strength after aging. Ti-6Al-4V (TC4) is lighter than steel at similar strength but cuts slowly and wears tools fast, so expect longer cycle times and a higher price per part. Inconel goes further into heat resistance and is harder again.
Non-metallics have their own rules. PEEK and POM handle insulators and bushings. Carbon fibre reinforced polymer gives stiffness at low weight but is abrasive, so tool life drops and dust control becomes a real requirement.
- 1Aluminium6061, 6061-T6, 2024, 5052, 5083, 6063, 6082, 7075, ADC12
- 2Stainless303, 304, 316, 316L, 420, 430, 431, 440C, 17-4PH (SUS630)
- 3Titanium and specialTA1, TA2, TC4 (Ti-6Al-4V), Inconel, magnesium AZ31B / AZ91D
- 4PlasticsABS, PC, PMMA, POM, PA, PEEK, PP, HDPE, carbon fibre
Certification scope and inspection: what to verify
Certificates are easy to print and hard to interpret. ISO 9001:2015 says the quality system is audited. IATF 16949:2016 adds automotive process discipline. ISO 13485:2016 covers medical devices and ISO 27001:2022 covers information security. None of these is AS9100 or NADCAP, so if your program requires those, ask directly and expect a straight answer.
Inspection is where the tolerance claim gets tested. A shop that inspects 100% before shipment, checks raw material on arrival, monitors in-process, and runs a final inspection gives you a paper trail. Reports come on request. Ask what is measured, on which machine, and how the results are stored.
Material traceability is the other half. For flight hardware you need to know the heat number and the mill certificate behind the bar stock. If the shop cannot link a finished part back to a material lot, the certificate on the wall does not help you.
- 1Ask for scopeWhich processes and sites does the certificate actually cover?
- 2Ask for reportsDimensional reports and material certs on request, not on promise.
- 3Ask about handlingSecure and confidential uploads, NDA available on request.
Lead time, volume, and the real cost drivers
Quotation and free DFM analysis come back within 12 hours. Production can start within 24 hours after that, and parts ship in 3–5 days for straightforward work. Historical late-delivery probability sits below 2%. Those numbers assume a clean drawing and available material, so treat them as the shop's baseline, not a guarantee for your part.
Volume changes the economics. There is no minimum order quantity, so one prototype and a 10,000+ part run both fit the same process. Prototype work usually costs more per part because setup is spread over fewer pieces. Production runs amortise setup and can justify a dedicated fixture.
Cost drivers are predictable: material grade, feature count, tolerance band, surface finish, and how many setups the part needs. Titanium and Inconel cost more to cut than aluminium. A tight Ra 0.2–0.8 μm finish adds polishing or fine finishing time. Adding a ±0.005 mm callout on a non-critical surface just adds inspection cost for no benefit.
- 1PrototypeOne part, fast turnaround, validate fit and function.
- 2BridgeSmall batch to cover testing while tooling is prepared.
- 3Production10,000+ parts with fixtures and process control.
Surface finishing and marking for aerospace parts
Finishing is not cosmetic on aerospace hardware. Anodizing adds corrosion resistance and can be clear, coloured, hardcoat, or conductive depending on the requirement. Electroless nickel, zinc, silver, and gold plating serve different electrical and wear needs. Powder coating and black oxide cover other cases.
Mechanical finishes change dimensions slightly. Bead blasting, tumbling, brushing, and polishing all remove or move material at the surface, so specify them before final inspection if the tolerance is tight. Hardcoat anodizing builds a layer and can shift a dimension by a few micrometres.
Laser marking and engraving handle part numbers, lot codes, and traceability marks. Minimum character height is 1.5 mm, which matters when you are marking a small bracket. Plan the mark location so it does not sit on a sealing face or a fatigue-critical edge.
- 1AnodizingClear, colour, hardcoat, conductive
- 2PlatingElectroless nickel, zinc, silver, gold
- 3MechanicalBead blasting, tumbling, brushing, polishing
- 4MarkingLaser marking and engraving, minimum character height 1.5 mm
How to release an aerospace part to a CNC shop
Follow these steps to avoid the most common delays.
- 1Send the 3D model and a 2D drawingThe model defines geometry; the drawing defines tolerance, finish, and datums. A model alone leaves critical callouts open to interpretation.
- 2State the material grade and conditionWrite 7075-T6 or 17-4PH (SUS630), not just aluminium or stainless. Grade changes cutting parameters and cost.
- 3Flag only the tolerances that matterApply ±0.005 mm to functional features. Blanket tight tolerances across the whole part add inspection time and cost.
- 4Request DFM feedback with the quoteA 12-hour quote with free DFM analysis should call out thin walls, deep pockets, and features that need a special tool.
- 5Confirm inspection and reporting needsSay up front whether you need dimensional reports, material certificates, or first article inspection.
- 6Agree on finishing and marking before cuttingAnodizing, plating, and laser marking affect dimensions. Decide the sequence so final inspection reflects the finished part.
- 7Protect your design dataUploads are secure and confidential. An NDA is available on request if your program requires one.
Frequently asked questions
What tolerance can CNC machining services for aerospace actually hold?
GreatLight works to ±0.005 mm (±0.0002 in) on critical features, with a 99.99% qualification rate across inspected parts.
That number depends on material and geometry. Titanium and thin-wall structures deflect more than a solid aluminium block, so discuss the part before committing to the band.
Do you have AS9100 or NADCAP certification?
The certifications held are ISO 9001:2015, IATF 16949:2016, ISO 13485:2016, and ISO 27001:2022.
If your program requires AS9100 or NADCAP, say so early. We will tell you plainly whether we can meet it rather than claim a scope we do not hold.
What is the minimum order quantity?
There is no minimum order quantity. One prototype and a 10,000+ part run use the same process.
Per-part cost is higher on a single prototype because setup is not spread across a batch.
How fast can parts ship?
Quotation and free DFM analysis come back within 12 hours. Production can start within 24 hours, and parts ship in 3–5 days.
Historical late-delivery probability is below 2%. Material availability and drawing clarity affect the actual date.
Can you machine titanium and Inconel?
Yes. Titanium grades include TA1, TA2, and TC4 (Ti-6Al-4V). Inconel is also machined.
Both wear tools faster than aluminium and cut slower, so expect longer cycle times and a higher price per part.
How do you handle confidential designs?
Uploads are secure and confidential. A non-disclosure agreement is available on request.
For defence-adjacent or proprietary programs, tell us at the quote stage so the right handling applies from the first file transfer.
Send your drawing, get a quote in 12 hours
Upload your model and drawing for free DFM analysis and a quotation within 12 hours. One prototype or 10,000+ parts, no minimum order quantity.
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