Aerospace CNC machining is defined by three demands that rarely relax: tight tolerances, full material traceability, and repeatable results across low and mid volumes. A bracket that flies has to match its drawing, and it has to be provable years later. This guide walks through the tolerances, materials, inspection, and cost structure that a buyer or design engineer should expect when sourcing precision aerospace CNC parts.
Tolerances in Aerospace CNC Machining
Most aerospace prints mix general profile tolerances with a handful of critical features that carry the tight callouts. Typical ranges we hold in production:
- General machined features: +/-.005 in profile
- Fit and bearing bores: +/-.001 in to +/-.0005 in
- Critical datums and dowel holes: +/-.0002 in to +/-.0005 in
- True position on hole patterns: .003 in to .010 in diametral zone
- Flatness and parallelism on mating faces: .0005 in to .002 in
Surface finish callouts drive process choice. A sealing face may specify Ra 16 uin, a general milled surface Ra 63 uin, and a bore for a dynamic seal Ra 8 to 16 uin. Reaching Ra 16 or better on hard alloys usually means a finishing pass with a dedicated tool, tighter stepover, and controlled coolant, which shows up in machine time.
Geometric Dimensioning and Tolerancing
Aerospace drawings lean heavily on GD&T. Position, profile, flatness, and runout controls tell us how to fixture and how to probe. When a datum scheme is well defined, we can build a CMM program that measures the part the way the designer intended, which reduces argument about whether a feature is in tolerance.
Materials and Certifications
Flight hardware lives and dies on the paper behind the metal. We machine to DFARS-compliant material with mill certifications that trace each lot back to a domestic or qualified source. Common aerospace grades and where they show up:
- 6061-T6 and 7075-T6 aluminum: brackets, housings, structural fittings
- Ti-6Al-4V titanium: high strength to weight parts, fittings, and clamps
- 15-5 PH and 17-4 PH stainless: shafts, pins, and load-bearing hardware
- Inconel 625 and 718: hot-section and high-temperature components
- A286 and 300-series stainless: fasteners and fixture-grade parts
Every lot ships with a certificate of conformance and, when required, the mill test report tied to the heat lot. Titanium and nickel alloys machine slower than aluminum, so a titanium fitting can take three to five times the cycle time of the same geometry in 6061. Plan quotes and lead times accordingly.
Traceability and Inspection
Traceability is a chain: heat lot to raw stock, stock to work order, work order to serial or lot number, and finished part to inspection record. We hold that chain so an out-of-tolerance report can be traced to a specific batch and a specific setup.
Inspection typically includes first article inspection to AS9102-style layouts, in-process checks, and final CMM inspection on our Brown & Sharpe coordinate measuring machine. A ballooned drawing turns into a numbered report where each characteristic is measured and recorded. For critical hole patterns and profiles, the CMM report is the document that closes the loop. Learn more about our inspection and quality process.
Choosing the Right Process
Aerospace parts split naturally across turning, milling, and Swiss:
- Shafts, spacers, and round fittings: CNC turning on multi-axis lathes
- Brackets, housings, and prismatic parts: CNC milling on horizontal machining centers
- Small-diameter pins, connectors, and long slender parts: Swiss machining for parts under about 1.25 in diameter
Aerospace CNC Machining Cost Drivers
Cost on a flight part is rarely just the metal. The table below shows typical illustrative estimates for a mid-complexity aluminum aerospace bracket in a lot of 25 to 100 pieces. These are ranges for planning, not binding quotes.
| Cost Driver | What It Covers | Typical Range |
|---|---|---|
| Setup | Programming, fixturing, first-piece proveout | $300 to $1,200 per setup |
| Material | Certified stock, 6061 or 7075, with drops | $8 to $60 per part |
| Machine time | Cycle time at shop rate | $18 to $45 per part |
| Finishing | Deburr, anodize, chem film, or passivate | $5 to $35 per part |
| Inspection | FAI plus sampling CMM reports | $150 to $600 per lot |
Titanium and Inconel parts move the machine-time and tooling lines up sharply. A titanium fitting can carry two to four times the per-part machine cost of aluminum because of slower speeds, higher tool wear, and more frequent tool changes.
Lead Times
Typical lead time for a proven aerospace part runs 3 to 6 weeks depending on material availability and finishing. First articles add 1 to 2 weeks for the layout and documentation. Rush work on aluminum with stock in house can ship in 7 to 10 business days.
Working in Canastota, New York
Wexmar runs turning, milling, and Swiss under one roof in Canastota, NY, with in-house CMM inspection and made-in-USA material. We are SAM.gov and CAGE registered and ship nationwide. For a fast turnaround estimate, use our instant quote tool and attach your drawing and material callout.