CNC Machining Aircraft Parts

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  What CNC machining aircraft parts really means
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  Which alloys suit which aircraft components
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  Where 5-axis helps and where it does not
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  How tolerance and inspection are held
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  What moves cost on an aircraft part quote
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  Choosing the right process for each aircraft part

CNC machining aircraft parts means cutting a solid billet into a finished airframe or engine component with a program-controlled tool path. Nothing is cast into shape first, so the part carries the mechanical properties of the parent material through its whole section. That matters for brackets, ribs, fittings and housings where grain direction and fatigue life are checked.

Most aircraft parts are not machined from one block without thought. A typical drawing specifies the alloy, the temper, the grain flow direction and the critical surfaces. The machinist then decides stock size, workholding and cut order. A 7075-T6 wing rib and a 6061-T6 access panel use the same machine but completely different feeds and spindle speeds.

Tolerances on aircraft work are tighter than general industrial work. Our standard machining tolerance is ±0.005 mm (±0.0002 in) on critical features. Surface finish usually lands between Ra 0.8 and 1.6 μm on functional faces, with Ra 0.2–0.8 μm available when a sealing face or bearing bore demands it.

The real constraint is not the machine. It is stiffness of the setup and heat in the cut. A thin 1.5 mm rib on a 4,000 mm part will deflect under cutting force no matter how accurate the spindle is. That is why setup planning matters more than the machine's spec sheet.

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  Material-driven speedsAluminum runs fast and dry; titanium runs slow with flood coolant.
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  Setup stiffness firstA weak fixture costs more tolerance than a worn tool.
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  Grain flow directionSpecify it on the drawing or expect the shop to guess.

Aluminum covers most non-hot sections. 7075-T6 gives the highest strength and is common for wing ribs, seat tracks and load-bearing brackets. 6061-T6 machines more easily and welds better, so it suits access panels, covers and non-structural housings. 2024 is chosen where fatigue resistance matters more than corrosion resistance.

Titanium is where the process slows down. Ti-6Al-4V (TC4) has roughly one third the thermal conductivity of aluminum, so heat stays in the cutting zone. Tool life drops, spindle speeds fall, and a part that takes 40 minutes in aluminum can take 4 hours in titanium. The payoff is strength-to-weight ratio and corrosion resistance without plating.

Stainless grades such as 17-4PH (SUS630), 316L and 440C appear in actuator parts, fasteners and valve bodies. Inconel is reserved for hot sections and exhaust-side hardware. Magnesium AZ31B and AZ91D show up in weight-critical housings, but they demand strict chip control because fine magnesium swarf ignites easily.

Plastics have a real place too. PEEK, POM and carbon fibre handle bushings, insulators and interior hardware. Carbon fibre is abrasive, so it eats carbide tooling quickly. Budget for more tool changes and slower feed rates on any carbon-filled part.

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  7075-T6High strength structural ribs and brackets.
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  6061-T6Panels, covers, housings, easy to weld.
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  TC4 / Ti-6Al-4VHot-adjacent and corrosion-critical parts.
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  17-4PHActuators, fasteners, valve bodies.

A 5-axis machining center reaches features that a 3-axis machine cannot without multiple setups. Contoured pockets, angled bosses and compound-angle holes can be cut in one clamping. Fewer setups means fewer datum shifts, and datum shifts are where most aircraft part errors come from. We run 16 simultaneous 5-axis centers, plus 12 four-axis mills and 27 three-axis machines.

Size drives machine choice. Our largest travel is 4,000 × 400 × 150 mm, which covers long spars and stringers. Medium work sits in the 750 × 1,150 × 550 mm and 600 × 600 × 600 mm envelopes. Compact parts like fittings run on 500 × 500 × 450 mm or 500 × 310 × 200 mm machines with a Ø400 mm rotary table for round work.

Five axes is not automatically better. A flat plate with simple holes is faster and cheaper on a 3-axis machine. Using 5-axis on simple geometry adds programming time and machine cost with no accuracy gain. The honest rule: reach for 5-axis when the part has angled features, deep contoured pockets, or features on four or more faces.

Thin-wall parts are the hard case. A wall under 2 mm on a long part will sing and deflect. The usual fix is to leave a support web, take light finishing passes, and cut the web last. Sometimes the right answer is to redesign the wall thickness rather than fight the machine.

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  Use 5-axisAngled faces, contoured pockets, multi-face features.
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  Use 3-axisFlat plates, simple hole patterns, high volume.
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  Thin wallsSupport web plus light finishing passes.

Tolerance on paper means nothing without inspection behind it. Every part we ship goes through 100% inspection. That covers incoming raw material checks, in-process monitoring during the cut, and a final dimensional inspection before packing. Reports are available on request for any order.

In-process checks catch drift early. When a tool wears, the cut gets slightly smaller. Measuring at fixed intervals lets the operator offset the tool before the feature leaves tolerance. On a long titanium run this is the difference between a good batch and scrap.

Temperature is the quiet error source. Aluminum expands roughly 23 μm per meter per degree Celsius. A part measured hot at 30 °C can read oversize against a drawing certified at 20 °C. For tight features, let the part settle to room temperature before final measurement.

Our certifications are ISO 9001:2015, IATF 16949:2016, ISO 13485:2016 and ISO 27001:2022. The ISO 27001 scope matters for aerospace customers because drawings and CAD files are controlled documents. Files stay confidential, and we sign an NDA on request before any data is transferred.

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  100% inspectionMaterial, in-process and final checks on every order.
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  Thermal settlingMeasure at 20 °C for features under 0.02 mm.
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  Document controlISO 27001:2022 covers uploads and drawings.

Quotes move mostly with material, not with machining time. Titanium and Inconel stock costs several times more than 6061 aluminum, and the scrap rate is higher. A part that removes 90% of its billet as chips is paying for metal that never ships. Near-net forgings or castings reduce that waste when volumes justify the tooling.

Feature count drives programming and cycle time. A bracket with 12 holes and one pocket is cheap. The same envelope with 40 holes, four compound angles and a sealing groove is not. Tolerances below ±0.005 mm add cost quickly because they need more measurement, slower finishing passes and sometimes a temperature-controlled check.

Finish adds a line item too. Anodizing, electroless nickel, zinc, silver and gold plating, powder coating and black oxide are all handled in-house. Bead blasting, tumbling, brushing and polishing handle cosmetic and functional surfaces. Laser marking is available down to 1.5 mm character height for part identification.

We take orders from one prototype to 10,000+ part runs with no minimum order quantity. Quotation and free DFM analysis come back within 12 hours. Production can start within 24 hours, and parts typically ship in 3–5 days. Historically, fewer than 2% of our orders ship late.

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  Billet-to-part ratioHigh chip volume means high material cost.
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  Feature countMore setups and angles, more programming and cycle time.
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  Tighter toleranceBelow ±0.005 mm adds inspection and finishing cost.