A supplier can send you a scanned business licence, a clean ISO certificate and twenty photographs of a machine hall, and still be the wrong shop for your part. Verification is not collecting documents. It is establishing three things: that the company you pay is the company that makes the part, that it has done your type of work before, and that you will be able to prove the parts are right before the balance is released.
We are a sourcing and freight team in Shenzhen, not a machine shop. Since 2019 we have run these checks for 4,000+ buyers shipping to 200+ countries. Our general factory verification guide covers the basics for any product. This one is specific to CNC machined and stamped metal parts, where the expensive failures are dimensional, not cosmetic.
- Match the legal entity on the licence, the contract, the invoice and the bank account.
- Ask which operations on your drawing are in-house and which are subcontracted.
- Send every shortlisted supplier the same complete RFQ pack, so quotes mean the same thing.
- Require itemised quotes. The lowest number is often a missing operation.
- Write three quality gates into the purchase order: first article, sealed sample, pre-shipment inspection.
- Agree who owns any tooling before you pay for it.
Start with the legal entity, not the website
The first check is boring and it catches more problems than any factory tour. Ask for the business licence and read the registered name character by character. Then compare it with the name on the proforma invoice and the name of the bank beneficiary. Those three should match. A quote from “Precision Co., Ltd” paid to an individual’s account, or to a differently named Hong Kong entity, is a different counterparty from the one you think you vetted.
| Check | What to ask for | What it rules out |
|---|---|---|
| Registered name and registration number | Business licence scan, plus the exact English name used on invoices | Shell intermediaries and name-swapping between quotation and payment |
| Business scope and establishment date | Licence details and the public enterprise registry entry | A company with no machining scope presenting itself as a manufacturer |
| Bank beneficiary | Account name on the proforma invoice | Payment diversion to a personal or unrelated account |
| Invoice capability | Sample of the commercial invoice and whether a formal VAT invoice is issued | Shipments that later cannot be declared cleanly at export |
Do the same for the address. A registered office in one city and a workshop in another is normal in China; an address that resolves to a shared office building and no workshop is a reason to ask the next question, not to end the conversation.
Factory or trading company, and why neither is automatically better
Buyers often treat “factory” as a pass and “trading company” as a fail. For a single-process turned part, working directly with the shop can be efficient. For a product that needs machining, stamping, anodising and assembly, an integrator may be the only realistic way to get one accountable party. The real risk is not the label, it is undisclosed subcontracting.
| Signal | Direct workshop | Trading company or sourcing agent |
|---|---|---|
| Equipment | Named machines, with axis count, travel and age | Named partner workshops and who runs each process |
| Quotation | Shop-level breakdown of machining and setup | Factory invoice shown separately from the service fee |
| Quality control | In-house measuring equipment and inspection records | Independent inspection with photos at each partner before consolidation |
| Accountability | One process, one responsible party | One contract covering several processes, with a single point of contact |
Whichever model you choose, ask one direct question: “Which operations on this drawing will be done in your own workshop?” A good answer names them. A vague answer usually means the plating, heat treatment or secondary machining is moving to a shop nobody has told you about. Our sourcing agent guide explains how we disclose that split.
Verify capability, not photographs
Machine-hall photographs are the least useful artefact in a supplier file. What you need is evidence that the specific geometry in your drawing is within that shop’s routine, not theoretically possible.
| Ask this | Why it matters | A weak answer |
|---|---|---|
| Machine list with travel, axis count and year | Determines whether your part fits the envelope and whether 5-axis work is genuinely in-house | “We have all kinds of machines” |
| Measuring equipment: CMM, height gauge, profile projector, roughness tester | A shop that cannot measure a tolerance cannot reliably hold it | Only calipers and a photograph of a report from another job |
| Two comparable parts made in the last year | Shows familiarity with your material, finish and tolerance class | Unrelated consumer products with no dimensions |
| Which certificate covers this work, and its scope and number | ISO 9001, IATF 16949 or AS9100 certificates are scoped to activities and sites | A PDF with no scope, no number, or a different company name |
| Material sourcing and mill certificates | Protects against grade substitution on aluminium and stainless | “Standard material, no problem” |
Ask for a short live video walk-through recorded that day, starting at the factory entrance sign, then the machine nameplates, then the inspection room. It is not an audit, but it makes staged photography much harder. A supplier who refuses a ten-minute walk-through while asking for a deposit has answered the question for you.
Also check process fit. If your part is thin, folded and vented, a machining shop may quote to mill it from solid when sheet metal fabrication is the right route; our process comparison sets out how to tell before you spend time vetting the wrong type of supplier.
Make the quotes comparable before you judge the price
Most quote spread comes from an incomplete RFQ, not from differences in efficiency. Send a neutral 3D model, a fully dimensioned 2D drawing with datums and general tolerance, material grade and condition, surface finish per feature, inspection requirements, packaging and destination, and quantity breaks in one request. The full file list is in our sourcing checklist.
Then require the quote to be itemised. At minimum: raw material, machine time, programming and setup, cutting tools or electrodes, any subcontracted finish, inspection and reporting, protective packaging, inland freight to the consolidation point, and separate one-off tooling or NRE. If a supplier will not split those lines, you cannot tell whether they are cheaper or simply quoting less work.
A quote far below the rest of the shortlist is usually a missing finishing step, an assumed material substitution or an inspection plan that does not exist. We show the factory invoice separately from our own fee so a buyer can audit every line, and we would rather explain a higher number than apologise for a missing operation three weeks later.
Three quality gates to write into the purchase order
Verification does not end when the order is placed. Put the following gates in the purchase order itself, not in an email thread, and tie the balance payment to them.
| Gate | When | What you receive | If it fails |
|---|---|---|---|
| First article inspection | Before production runs | A full dimensional report against every numbered feature on the drawing, with material certificate | Correct the program or fixture and re-submit; no production release |
| Sealed golden sample | After the first approved run | A signed, dated, tagged sample held by both sides as the visual and cosmetic reference | Re-approve the sample before shipment; do not rely on photographs |
| Pre-shipment inspection | After production, before goods leave the consolidation warehouse | A photo report with dimensional checks, quantity, workmanship and packaging | Rework or re-make in China, where it is still cheap to fix |
We sample to AQL 2.5 for general workmanship, but sampling alone is not enough for precision parts. Agree separately that critical and safety-related dimensions are checked on every piece, or at a documented rate you accept, and state which dimensions those are on the drawing. An AQL level describes a sampling plan; it is not a promise that every bore is in tolerance.
Red flags we treat as stop signs
- The bank beneficiary is an individual or a company with a different name from the licence.
- No live walk-through, no machine nameplates, and no dated evidence of the workshop.
- A certificate with no scope or number, or a scope that does not cover machining.
- A detailed quote returned in minutes with no questions about your drawing. Somebody did not open it.
- Refusal to put inspection gates in the purchase order, or to accept a balance held until the report is approved.
- Unclear tooling and drawing ownership, especially on stamped parts. The clause that settles this is set out in our tooling ownership guide.
- No material certificates for grades where substitution is easy and hard to detect later.
What changes when someone sits on your side of the table
A factory verifies itself flatteringly. An independent team verifies against your drawing and your purchase order, and can recommend a different supplier without losing a sale. That is the position we take: we shortlist vetted workshops, sit in on the technical review, hold the sample and inspection records, and if a supplier fails a gate we can move the work rather than defend the choice.
It also solves the multi-supplier problem. When machining, stamping and finishing sit in three different workshops, someone has to reconcile the parts before they share a carton. Our consolidation process brings them into our Shenzhen warehouse for a final check and one customs entry, so the buyer gets one inspection report, one invoice and one tracking link instead of three partial shipments.
Frequently asked questions
How do I check whether a Chinese supplier’s ISO certificate is genuine?
Ask for the certificate number, the certification body, the site address and the exact scope of activities, then verify them with that certification body rather than trusting the PDF. Check that the company name matches the business licence and that the scope covers the process you are buying. A certificate for trading or assembly does not cover machining.
Should I avoid trading companies for machined parts?
Not automatically. A trading company or sourcing agent is a risk when it hides who makes the part, and an advantage when it coordinates several processes, shows the factory invoice separately and puts one party on the hook for all of them. Ask for the named workshop and the split of operations, then verify that workshop too.
What is a first article inspection report and do I really need one?
It is a dimensional report for the first part off the production process, measured against every numbered feature on your drawing, usually with material and finish evidence. For any part where a wrong dimension would stop an assembly line, yes. It catches program, fixture and interpretation errors before an entire batch is made.
Is AQL 2.5 enough for precision machined parts?
It is a reasonable sampling level for general workmanship, appearance and quantity. It is not a substitute for defining critical characteristics. Mark the critical dimensions on the drawing and agree how those are checked, either on every piece or at a documented full-report rate, before production starts.
Can I verify a supplier without flying to China?
Most of the risk can be closed remotely: entity and bank checks, certificate verification, a dated live walk-through, comparable part evidence, an itemised quote and a first article report. For a high-volume or safety-critical programme, an on-site audit before the first production release is still worth the trip, and a local team can run it on your behalf.
Send us your drawing, or a photo and a rough description, with your target quantity and destination country. We will shortlist workshops that actually make your part type, show the factory invoice separately from our fee, and come back within 24 hours with a comparison you can audit line by line. Send your requirement and we will start with the entity check.