On aerospace parts, the paper trail matters as much as the cut. A part with perfect dimensions and no material certificate, no first article record, and no traceability back to its heat of metal is not an aerospace part — it is an unverified part. The good news is that the documentation you need is fully available from a well-run China precision machining shop, as long as you specify it in writing before the PO instead of discovering its absence after the parts ship. This article walks through the four documents that matter most — material certificates, quality system evidence, first article inspection reports, and traceability records — and the tolerance questions you need to settle while the drawing is still being quoted.
What must a material certificate prove for an aerospace part?
Every aerospace drawing names a material by grade and condition: 6061-T6 aluminum, 17-4PH stainless in the H1025 condition, Ti-6Al-4V in the annealed or solution-treated condition. A mill test certificate, or material certificate, is the supplier's written evidence that the specific heat of metal meets the chemistry, condition, and mechanical properties of the standard you named on the drawing. It exists because you cannot verify the inside of a bar by looking at it, and the certificate is what lets a heat of material be released into an aerospace supply chain.
For a China precision machining supplier, the practical question is whether the stock it quotes and cuts is procured to your specification. When you send an RFQ, name the exact standard you want the material bought to — an AMS or ASTM specification with the condition and temper, not just an alloy nickname. Then state that the certificate must accompany the stock and that it will be checked against the drawing before machining starts. A shop that has to hunt for a certificate after the parts are made has already lost the traceability argument; the certificate has to exist at the receiving gate, tied to the physical material.
Which details on a material certificate should you actually read?
Buyers routinely check the alloy name on a certificate and stop there. On aerospace work, four more details decide whether the document is worth the paper. First, the heat or lot number must appear and must match the marking on the delivered bars or plate — without that link, the certificate describes a material, not your material. Second, the specification reference must be the one you flowed down, including the temper or condition. Third, where the standard calls for mechanical testing, the certificate should show actual test values, not a blank line or a generic statement of compliance. Fourth, the document must be in English, because the certificate is going into your quality file, and someone on your side will audit it.
There is one more gap that shows up specifically when sourcing aerospace material in China: the temptation for a local stockist to sell an "equivalent" grade at a lower price. Equivalent is not a defined word in aerospace procurement, and a shop that quietly buys a domestic equivalent to the AMS grade you specified has broken your material chain even if the chemistry happens to be close. Put the substitution rule in the RFQ: no grade substitution without written approval, and incoming verification against the certificate before the material is released to the machine. If a supplier will not commit to that in writing, treat the quote accordingly.
Which quality system certificates should an aerospace buyer look for?
Aerospace buyers ask two questions about quality systems, and they are easy to confuse. The first is whether the supplier holds a quality management system certificate at all. The second is whether that certificate is the aerospace one. Most machined parts that fly are made by a long chain of suppliers, and only a portion of that chain carries AS9100, the aerospace quality management standard. What actually reaches a machine shop is a set of flowed-down requirements from the prime or the airframer, written into the contract, covering first article inspection, material certification, traceability, and record retention.
That is why the practical starting point for a China precision machining shop is a certified ISO 9001:2015 quality system, and many shops that serve the automotive and medical sectors go further. The factory behind this site, for example, is ISO 9001:2015, IATF 16949:2016 (product design excluded) and ISO 14001:2015 certified, with the details on its quality page. The aerospace-specific layer — AS9100 certification, or simply the contractual flow-down of AS9102 first article inspection and material records — is then written into your purchase order. If your program genuinely requires the shop to hold AS9100, ask for a copy of the certificate and read the scope, because the scope names the processes and locations it covers. Do not accept the words "we work to AS9100" without the certificate in your hands.
What should a first article inspection report contain?
The first article inspection, or FAI, is the single most useful document a buyer receives from a new aerospace machining supplier, because it proves the shop measured the part rather than assumed it. Under AS9102, the report documents the first production part against every characteristic on the drawing: each dimension and tolerance, the geometric callouts, the notes, the material condition, and the surface finish. For every characteristic the report lists the required value from the drawing, the measured value from the part, the instrument used, and a conformance decision. A characteristic that does not conform is flagged for disposition rather than quietly corrected.
For a buyer, the FAI does two jobs. It confirms the part matches the drawing before you authorize a production run, and it gives you a read on the supplier's measurement discipline — a report where every box is filled and the instrument names are plausible is worth more than ten phone calls. Ask for the FAI on the first article to be sent before the balance of the order is released, and schedule your review time. A fresh FAI is triggered not just by a new part but by a design revision, a change of material source, or a change of process, so state in the PO that any of those events requires an updated report. The parts page of this site shows the kind of work the review applies to.
How far back should traceability reach on machined aerospace parts?
Traceability on a machined part is a chain with four links. The first link is the material certificate tied to the heat number of the stock that was actually cut. The second is the record of that stock going into a specific job — the lot number, the date, the work order. The third is the process record: which machine cut the part, which program revision, which operator, and what the inspection results were. The fourth link is the finished part itself, which for aerospace work is often marked with a part number, a serial number, and sometimes the heat or lot reference so the chain can be walked in either direction.
When you qualify a China precision machining supplier, do not accept a description of its traceability system; ask to see the chain demonstrated on a completed order. Pick a past job and ask for the material certificate, the work order, and the inspection record for the same lot, and confirm they reference one another. Also check the mundane details that break chains in practice: two heats of material used in the same batch and mixed at the deburr bench, records that exist only in Chinese when your auditor reads English, or certificates that reference the material family rather than the specific heat. Agree on record language, retention period, and part marking before the PO so the chain is built in from the first lot.
Which tolerances are realistic on aerospace machined features?
Aerospace drawings carry some of the tightest tolerances in manufacturing, but tight is expensive and slow, so the buyer's job is to put tolerance where function needs it. On precision machining work in China, the realistic envelope is the same as anywhere: milling and turning hold ±0.003 mm on controlled features, precision grinding reaches ±0.002 mm, and the process capability target on critical characteristics is Ppk ≥ 1.67 initial. Those numbers are achievable, but they come with two conditions a buyer must manage. The first is that capability has to be proven per feature, from measurement data, not asserted in a quote. The second is that a ±0.003 mm callout means nothing until the drawing defines the datum scheme, because the part will be measured differently on different locating surfaces and both readings can be internally consistent.
Express critical features with GD&T against explicit datums, and specify the reference condition: dimensional measurement references 20 °C, and aluminum expands around 23 micrometres per metre per degree Celsius, so a long feature measured on a warm shop floor will disagree with the same feature measured in a metrology lab. Decide where critical features get measured — a CMM rather than a hand gauge — and which instrument wins if the numbers disagree. On an aerospace part, this is not bureaucracy; it is the difference between a part accepted on evidence and a part accepted on trust.
Which aerospace alloys are realistic to machine, and where does the cost go?
Material choice drives both price and lead time on aerospace machining more than any other single factor, because the alloys differ enormously in how they cut. The table below summarizes what a buyer typically sees on machined aerospace parts sourced from China.
| Alloy | Typical aerospace use | Machining reality |
|---|---|---|
| 6061-T6 aluminum | Brackets, housings, non-structural hardware | Cuts fast and predictably; lowest cost and shortest lead time |
| 7075-T6 aluminum | High-strength airframe brackets and fittings | Machines well but thin walls can move as stress is released; specify stress-relieved stock |
| 304 / 316L stainless | Cabin hardware, corrosion-exposed parts | Work-hardens; moderate cutting speeds, moderate cost |
| 17-4PH stainless (H900, H1025) | High-strength corrosion-resistant fittings, actuators | Usually machined in the annealed condition, then heat treated; adds process steps and inspection |
| Ti-6Al-4V (Grade 5) | Structural parts where strength-to-weight matters | Slow cutting, rigid setups, higher tooling cost; premium price and lead time |
| Inconel 718 | Parts near heat sources | Very slow cutting with high tool wear; the most expensive row on the list |
Two buying rules follow. First, only specify an exotic alloy where the application demands it — a 7075 part redesigned to 6061, or a 17-4PH part moved to a stronger aluminum, can cut cost sharply without changing function. Second, confirm before quoting that the shop can source the grade you want with a traceable certificate. Titanium and nickel alloys are expensive enough that some suppliers quote an equivalent grade to win the order; the RFQ should name the standard, require the certificate at receiving, and treat substitution as a rejection.
Which questions belong on your RFQ for aerospace machined parts?
Everything above condenses into a short list of questions that should travel with the first RFQ. Send them before you compare prices, because the answers change what the prices mean.
- Material: Will you procure to the AMS or ASTM standard I name, on the grade and condition on my drawing, with the certificate at receiving? May I see the certificate format you issue?
- First article: Will you produce a first article inspection per AS9102 on the first part, and send it for review before the production run? What events trigger a new report?
- Tolerance evidence: For my critical characteristics, which instrument will measure each one, and can you provide capability data at Ppk ≥ 1.67 initial once the process is stable?
- Traceability: What does your lot record capture — heat number, machine, program revision, operator, inspection results — and in which language? How long do you retain it?
- Process control: How do you handle a drawing revision that arrives after programming? How do you quarantine and report a non-conforming lot?
- Records and marking: Will parts be marked with part number and lot, and will reports, certificates, and the packing documents all be in English?
A supplier that answers these with named documents and a named process is telling you the truth about its systems. A supplier that answers with assurances and enthusiasm is telling you about its sales desk. Price matters, but on aerospace work the documentation cost is part of the part — a missing certificate or a first article that was never measured surfaces later as a rejected shipment, a grounded lot, or an audit finding on your side of the table.
The buyer's rule of thumb: treat the certificate, the first article report, and the traceability record as deliverables with a date, the same way you treat the parts. If a supplier cannot commit to them in the quotation, the quotation is incomplete.
Frequently Asked Questions
Can a China precision machining shop really meet aerospace material and documentation requirements?
Yes, when the requirements are written into the order. Certified shops buy traceable stock, hold incoming material records, and produce first article reports on request. The verification step is always the same: ask to see the documents for one completed order and check that the heat number, the certificate, and the inspection record line up.
Is AS9100 required for every aerospace part machined in China?
No. Flight-critical hardware under a prime's approved-supplier system usually requires AS9100 with a verifiable certificate scope. For non-flight-critical machined parts, a certified ISO 9001:2015 quality system plus contractual flow-downs such as AS9102 first article inspection and material certificates is the common arrangement, and it works when the requirements are explicit.
What tolerances should I specify, and what can a precision machining shop hold?
Milling and turning hold ±0.003 mm and precision grinding holds ±0.002 mm, with process capability Ppk ≥ 1.67 at the initial study on critical characteristics and Cpk ≥ 1.33 on general characteristics. Capability is reported per characteristic: every report names the feature, its tolerance band, the sample size, the sigma method, and the study window. Specify tight tolerance only where function needs it, define datums, and require measurement on a CMM rather than accepting a blanket claim.
What is the difference between AS9100 and AS9102?
AS9100 is the aerospace quality management system certification a company holds, covering its whole operation. AS9102 is the standard that defines the first article inspection report itself — the form and content of the document proving the first part meets every drawing characteristic.
Can the supplier buy the material, or should I supply it?
Both work, but supplier-bought material is the norm when the RFQ names the exact standard and requires the certificate at receiving. Consigning your own approved material removes the substitution risk entirely and is worth it for flight-critical alloys, at the cost of managing the logistics yourself.
What happens if the first article does not conform?
The report flags the characteristic for disposition instead of quietly fixing it. Agree before the PO on the process: the supplier quarantines the lot, sends the non-conformance report, and rework or re-run happens only with your written approval. That agreement is what turns a discrepancy into a controlled event.
Do I need a third-party inspection before the parts ship?
Not always. Reviewing the first article and the material certificates, then requiring pre-shipment photos and measurement data, covers many programs. For flight-critical hardware, or when the shop is new to you and you cannot visit, an independent inspection before the balance of payment is a reasonable gate.
Need a machining partner that will put the documentation in the quote?
Send the drawing, the material standard, and your documentation requirements through the contact page — the review will come back with the material, tolerance, and documentation plan stated in writing.