Submitted by jeingham on

Aerospace machining is not general machining with a certification sticker. The tolerances are tighter, the materials are harder, the documentation requirements are heavier, and the consequences of getting it wrong are measured in lives, not dollars. If you're sourcing aerospace machined parts, the shop you choose needs more than good equipment — they need the systems, the discipline, and the paper trail to prove it.

This guide covers what makes aerospace machining different, which certifications actually matter, and how to find qualified shops in the Machinist.com directory.

What Makes Aerospace Machining Different

Materials

Titanium (Ti-6Al-4V), Inconel, Hastelloy, 15-5 PH stainless, aluminum 7075-T6. These aren't forgiving materials. Titanium work-hardens if you look at it wrong. Inconel eats tooling. Shops that run these materials daily have the speeds, feeds, and tooling strategies dialed in — shops that run them occasionally don't.

Material selection in aerospace isn't a suggestion — it's specified by the prime or the design authority, and substitutions require formal approval. The shop needs to source material from approved mills, verify chemistry and mechanical properties through mill certifications, and maintain full traceability from raw stock to finished part. A shop that buys surplus material off a broker without proper documentation isn't an aerospace shop — they're a liability.

Tolerances

±0.0005" or tighter is common on aerospace work. That requires thermal stability, proper fixturing, and in-process inspection — not just a capable machine. A shop that holds ±0.001" all day on commercial work may struggle when aerospace specs cut that in half.

Aerospace tolerances also come with formal verification. It's not enough to hit the dimension — you need to prove it with calibrated instruments, documented measurements, and inspection reports that tie every reading to a specific serial number and operation. The measurement system itself may need to be validated (Gage R&R studies are common requirements).

Surface Finish

Ra 16 µin or better is typical for structural components. Flight-critical parts often require Ra 8 or finer. Meeting these specs consistently — not just on a sample piece — takes process control, not just good tooling.

Documentation

First Article Inspection (FAI) per AS9102, full material traceability (mill certs tied to individual lots), process documentation, and often source inspection by the prime or their designee. If a shop treats paperwork as an afterthought, they're not an aerospace shop. The paper trail is the product as much as the part is.

Aerospace documentation requirements go beyond what most commercial buyers encounter. A typical aerospace job file includes:

  • Purchase order with flow-down clauses from the prime
  • Material certifications with chemical and mechanical test results
  • Process travelers documenting each operation, operator, and date
  • In-process and final inspection records
  • First Article Inspection Report (FAIR) per AS9102
  • Certificate of Conformance (CoC)
  • Non-conformance reports for any deviations, with disposition
  • Packaging and preservation records per MIL-STD-2073 or customer spec

This documentation exists so that 20 years from now, if a component fails in service, the investigation can trace exactly what material was used, who machined it, what machine they used, and what the inspection results were. That level of traceability is expensive to maintain — and non-negotiable.

Types of Aerospace Work

Not all aerospace machining is the same. The requirements, certifications, and supply chain structures differ significantly by sector.

Commercial Aviation

Parts for Boeing, Airbus, and their tier suppliers. AS9100 is the baseline. The work is often high-volume by aerospace standards — hundreds or thousands of brackets, fittings, and structural components per aircraft program. Shops in this segment need capacity, consistency, and on-time delivery performance tracked to the decimal. Commercial aviation primes track supplier scorecards aggressively — late deliveries or quality escapes can get a shop removed from the approved supplier list.

Defense and Military

Fighter aircraft, missiles, naval systems, ground vehicles. Same quality requirements as commercial aviation, plus ITAR registration, DFARS compliance, and often facility security clearances. Defense work tends toward lower volumes but higher complexity — and the customer's quality oversight is more hands-on. Expect source inspections, DCMA (Defense Contract Management Agency) involvement, and formal government property management if they furnish material.

Space and Satellite

The highest stakes. Space hardware doesn't get repaired in service. Parts for launch vehicles, satellites, and crewed spacecraft face the most rigorous inspection and documentation requirements in manufacturing. Materials are exotic, tolerances are extreme, and every part is essentially a prototype. Shops in this niche are highly specialized — they build their business around a small number of programs and invest heavily in process validation.

Maintenance, Repair, and Overhaul (MRO)

Replacement parts for aircraft in service. MRO machining requires the same certifications as new production, but adds complexity: parts may need to be reverse-engineered from worn originals, manufactured to superseding specifications, or produced in very small quantities (sometimes single pieces). Shops serving MRO need flexibility and fast turnaround — an aircraft on the ground is losing money every hour.

Common Aerospace Part Types

Understanding what shops typically make helps you evaluate whether a shop's experience matches your needs.

  • Structural components: Ribs, spars, bulkheads, frames, gussets — often machined from solid billets of 7075-T6 or 7050-T7451 aluminum. These are large, thin-walled parts with complex pocketing. Five-axis machining is common.
  • Engine components: Turbine blades, compressor discs, combustion chamber housings — typically Inconel, titanium, or nickel superalloys. Extreme tolerances, complex geometries, and materials that punish bad machining parameters.
  • Fittings and brackets: Mounting hardware, actuator brackets, hydraulic fittings. High volumes relative to other aerospace parts. Stainless steel, titanium, or aluminum depending on application. Simpler geometry but strict quality requirements.
  • Landing gear components: High-strength steel (300M, 4340, Custom 455) machined to tight tolerances. Often require heat treatment, shot peening, and non-destructive testing (magnetic particle or fluorescent penetrant inspection).
  • Avionics housings: Enclosures for electronic systems. Typically aluminum with EMI shielding requirements. Complex internal geometry, thin walls, tight flatness specs, and often chemical conversion coating (MIL-DTL-5541) or hard anodize.

Certifications That Matter

AS9100 / AS9100D

The baseline. AS9100 is the aerospace quality management standard, built on ISO 9001 with additional requirements for risk management, configuration management, and product safety. If a shop isn't AS9100 certified, most aerospace primes won't consider them. We list over 540 AS9100-certified shops in our directory.

Browse AS9100-certified shops →

ITAR Registered

Required for any work involving defense articles or technical data controlled under the International Traffic in Arms Regulations. ITAR isn't a quality cert — it's a legal requirement. Shops handling ITAR-controlled work must be registered with the Directorate of Defense Trade Controls (DDTC). Non-compliance carries criminal penalties. We list 345 ITAR-registered shops.

Browse ITAR-registered shops →

NADCAP

National Aerospace and Defense Contractors Accreditation Program. This is a special process accreditation — heat treating, welding, non-destructive testing, chemical processing, coatings. If your part requires any special process, the shop (or their sub) needs NADCAP accreditation for that specific process. General machining doesn't require NADCAP, but most aerospace parts touch at least one special process. We list 38 NADCAP-accredited shops.

Browse NADCAP-accredited shops →

DFARS Compliant

Defense Federal Acquisition Regulation Supplement. Relevant for defense contracts — requires domestic sourcing of certain specialty metals and compliance with cybersecurity requirements (NIST SP 800-171 / CMMC). If you're a defense contractor flowing down DFARS clauses, your supply chain needs to comply. 44 shops in our directory are DFARS compliant.

Browse DFARS-compliant shops →

CAGE Code

Commercial and Government Entity code. Required for any company doing business with the U.S. Department of Defense. It's a registration, not a quality certification, but it's a prerequisite for defense work. 942 shops in our directory have a CAGE code.

Browse CAGE-registered shops →

Supply Chain and Flow-Down Requirements

Aerospace supply chains are layered. Understanding where you sit in the chain determines what requirements flow down to your machine shop.

Primes (Boeing, Lockheed Martin, Raytheon, Northrop Grumman) set the top-level requirements. Tier 1 suppliers make major assemblies and subcontract machining to Tier 2 and 3 shops. Each tier flows down quality, material, and compliance requirements to the next.

As a buyer at any tier, you're responsible for ensuring your suppliers meet the flowed-down requirements. That means:

  • Approved Supplier Lists (ASL): Most aerospace companies maintain a formal list of approved suppliers. Getting on the list requires a quality audit, capability review, and often a trial order. This process takes 3–6 months.
  • Quality clauses: Your purchase order should include specific quality clauses that flow down requirements from the prime. These cover inspection, documentation, material sourcing, non-conformance handling, and right of access for customer quality representatives.
  • Sub-tier management: If your machine shop sends parts out for heat treating, plating, or NDT, those sub-tier vendors also need to meet the flowed-down requirements. You're responsible for your supply chain — the prime holds you accountable, not your vendors.

How to Find Aerospace Machine Shops

The Machinist.com directory lists over 1,100 shops serving the aerospace and defense industries. You can narrow the list several ways:

Search Aerospace Machine Shops →

What to Ask Before You Send the RFQ

Once you've shortlisted shops, these questions separate the qualified from the hopeful:

  • Are you AS9100 current? Ask for the certificate — the expiration date matters. Lapsed certs happen more than they should.
  • What aerospace primes have you worked with? Direct experience with your prime's quality requirements saves weeks of onboarding.
  • Do you do your special processes in-house or sub them out? If subbed, are the subs NADCAP-accredited? You're responsible for your supply chain.
  • What's your typical lead time for first articles? Aerospace first articles take longer than commercial work. A shop that quotes the same lead time for both isn't accounting for the documentation overhead.
  • Can you handle source inspection? If your prime requires source inspection, the shop needs a dedicated area, a process for scheduling, and people who've done it before.
  • What's your reject rate on aerospace work? Good shops track this number. If they can't answer, that tells you something about their quality system.
  • What's your on-time delivery rate? Aerospace primes track this metric aggressively. A shop that can report their OTD percentage — and it's above 90% — has the scheduling discipline the work requires.
  • How do you handle non-conforming material? The answer should involve a formal process: segregation, documentation, disposition (use-as-is, rework, scrap), and root cause analysis. "We catch it and fix it" isn't a process — it's a hope.

The Short Version

Aerospace machining is defined by its consequences. The materials are demanding, the tolerances are tight, and the documentation requirements exist because people's lives depend on the parts. Choosing a shop for aerospace work isn't about finding the cheapest quote — it's about finding a shop with the right certifications, the right experience, and the systems to prove every part was made correctly.

Start with the certification filter. AS9100 is the minimum. ITAR for defense. NADCAP for special processes. Then verify experience in your specific sector and part type. A shop that machines aluminum brackets for commercial aviation is a different operation than one that makes Inconel turbine components for military engines — both are aerospace, but they're not interchangeable.

Request a Quote for Aerospace Machining → Submit your specs and we'll match you with AS9100-certified shops that have the capability and clearances your project requires.

Questions about sourcing aerospace machined parts? Contact us — we can help you navigate the directory to find shops that match your requirements.