Roughly one in three first orders to a new Chinese machining supplier goes wrong — not because the supplier cannot machine, but because the buyer never verified what they were actually buying.
This checklist lists the twelve checks that separate a real contract manufacturer from a trading company that forwards your drawing to an unknown workshop.
1. Verify the legal entity, not just the website
Ask for the business licence and cross-check three things: the registered company name, the registered capital, and the business scope. If “manufacturing” is absent from the scope, you are talking to a trader.
Also check the registered address against the factory address. A registered address in a downtown office tower with a factory “somewhere in Dongguan” is normal for large groups, but unusual for a 50-machine shop.
2. Confirm the certificate is real and current
ISO 9001:2015 is the baseline. Three things to verify:
- The certificate number — check it on the issuing body’s website, not on a photo of a framed certificate.
- The expiry date — certificates lapse. An expired ISO 9001 is not a certificate.
- The scope statement — it should name CNC machining (or your specific process), not just “trade of machinery.”
Do not accept IATF 16949 or ISO 13485 claims without a certificate. If a supplier says “we follow automotive standards,” that is not certification.
3. See the equipment list with model numbers
Ask for a machine list with brand, model, and year. Then ask for a video walkthrough showing the machines running. Any supplier can photograph a clean workshop; only a supplier who owns those machines can show them cutting metal on a five-minute unedited video.
Pay attention to the inspection equipment line. A ZEISS or Hexagon CMM, a profile projector, and a roughness tester indicate a shop that can prove its tolerances. If the list has only calipers, precision work is being verified by guesswork.
4. Match machine capability to your part size
A shop with only small 3-axis VMCs cannot produce a 1.2m long extrusion. Check the work envelope against your largest part dimensions, plus the fixturing allowance.
Also check for 5-axis and mill-turn capability if your part has compound angles or requires multiple faces with tight positional tolerance — otherwise it will be set up multiple times, and each setup adds stack-up error.
5. Understand the quoting structure
A one-line total price tells you nothing. A serious quote breaks down:
- Material cost with grade and mill certificate availability
- Machining time per operation
- Setup charge (or one-time tooling / programming fee)
- Surface treatment, and whether it is in-house or outsourced
- Inspection and documentation fees
- Packaging and shipping terms (FOB / CIF / DDP)
If the breakdown is absent, ask for it. A supplier who cannot explain where the price comes from cannot defend it when your volume changes.
6. Ask who does the surface finishing
Anodising, passivation, powder coating, and electroplating are almost always subcontracted by machining shops. That is fine — but you need to know:
- Which specific subcontractor
- Whether they are certified for the process
- Who is liable if the finish fails (usually the shop that quoted you — get that in writing)
Surface finishing is where most quality escapes happen, because the part leaves the supplier’s control.
7. Demand first article inspection (FAI) with real numbers
An FAI report should list every dimension on the drawing with the measured value, not just a pass/fail checkmark. The report should name the instrument used and the inspector.
Agree on FAI before the first production run. Review it line by line against the drawing. This is your only cheap opportunity to catch a misread drawing.
8. Get tolerance capability in writing
Ask directly: “What is your standard general tolerance, and can you hold ±0.01mm on the bore?”
The answer should be specific. If the supplier promises ±0.01mm on everything without asking which feature, they either do not understand tolerance or are telling you what you want to hear. Both are risks.
9. Verify material traceability
For anything structural, regulated, or safety-related, request mill certificates with the heat number. Check the grade matches the drawing — 6061 vs 7075 aluminium is a 2× material cost difference and a completely different machining behaviour.
Watch for substitutions on high-value alloys. Titanium and 17-4PH stainless are the most commonly substituted.
10. Test the engineering response
Send a drawing and ask for DFM feedback before you ask for price. A capable supplier will flag:
- Features that cannot be machined without a special tool
- Thin walls that will deflect
- Tolerances that are tighter than the function requires
- Sharp internal corners that will need EDM
Suppliers who only ever answer “yes, we can do it” without comment are order-takers, not manufacturing partners.
11. Agree on payment terms that protect you
Standard practice in China is 30% deposit / 70% before shipment. That is normal and acceptable for a first order.
What is not acceptable:
- 100% prepayment on a first order
- “Balance before shipment” with no inspection rights
- Any request to pay to a personal account rather than the company account
Build in your right to inspect before the balance is released. If your order value justifies it, use a third-party inspection (SGS, Bureau Veritas, TÜV) at pre-shipment.
12. Sign an NDA before sending full drawings
Send the NDA first, then the drawings. A supplier who hesitates on an NDA on a first enquiry is telling you how they treat intellectual property.
The NDA should cover: drawing confidentiality, no subcontracting without consent, no use of your parts in their portfolio, and a defined duration.
Red flags worth walking away from
- Price significantly below every other quote, with no explanation of why
- Refusal to provide a video walkthrough of the factory
- Quoting ±0.01mm without asking which feature
- No equipment list, or an equipment list with no model numbers
- Pressure to pay a deposit within hours
- Communication that suddenly slows down after the deposit is paid
A faster way to run this checklist
Most of these twelve checks can be completed in a single exchange:
“Please send: business licence, ISO 9001 certificate number and expiry, equipment list with models, a 3-minute video walkthrough, and your standard general tolerance. Here is our drawing — please give DFM feedback and a cost breakdown before quoting.”
A capable supplier replies within one business day with all six items. Everything you need to know about working with them is visible in how they answer that one message.
Where Mingxin fits
We are an ISO 9001:2015 certified factory in Xiamen, China, running precision CNC machining, sheet metal fabrication, injection molding, die casting, metal stamping, and 3D printing under one roof. 50+ engineers and technicians, ±0.01mm on functional features, 15+ years serving European and North American buyers.
If you want to run this checklist against us, start here — we will send everything above before you ask twice.
Request our factory documents and a line-item quote. NDA available before you share files.
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