How to vet a Chinese metal parts manufacturer before ordering

Sourcing metal parts from China can save 30 to 50 percent on unit cost. It can also cost you six months of delay, a container of scrap, and a customer who walks. I have seen both outcomes. The difference almost always comes down to how hard you vet the supplier before you send the first PO.

This guide breaks the vetting process into five stages. Each one filters out a specific type of risk. Skip any stage and you are betting money on a supplier you have never met.

Stage 1: verify the company is real

Before you ask about capabilities or pricing, confirm the company exists as a legal entity. I am surprised how many buyers skip this. A polished website and a quick WeChat reply do not prove anything.

Ask for a copy of the business license. It lists the registered company name, legal representative, registered capital, and scope of business. Cross-check the company name on the National Enterprise Credit Information Publicity System (gsxt.gov.cn). If the registered name on the license does not match the name on the website, ask why. Some trading companies use multiple English names. That is not automatically a dealbreaker, but you need to know who you are paying.

Registered capital matters less than people think. A company with 5 million RMB registered capital can be excellent. A company with 50 million can be a shell. What matters more is how long they have been operating. A manufacturer registered in 1998 has 27 years of survival behind it. That tells you more than any ISO certificate on the wall.

Check whether the company is a manufacturer or a trading company. Trading companies have their place. They can aggregate multiple processes and handle logistics. But if you think you are buying from a factory and you are actually buying from a trading company, you have a problem with pricing transparency and technical communication. Ask directly: "Do you own the factory?" Then verify the answer by asking for the factory address and checking it on Google Earth. If the address is an office building in a downtown district, you are not talking to a factory.

Stage 2: audit the quality system and certifications

Ask what certifications the supplier holds. For general industrial parts, ISO 9001 is the baseline. If the supplier does not have ISO 9001, walk away. I have tried working with non-certified shops to save money. The parts arrived, but the dimensional consistency was terrible and there was no corrective action system to fix it.

For automotive parts, IATF 16949 is mandatory. If a supplier claims IATF 16949 but cannot produce a certificate with a valid certificate number, do not accept "we are in the process" as an answer. Either they have it or they do not. You can verify IATF 16949 certificates through the IATF database or the certification body's website.

For aerospace parts, look for AS9100. For medical device components, ISO 13485. These are not nice-to-haves. They are regulatory requirements in your market, and your supplier needs to operate within the same framework if you want traceability.

One thing I always check: does the supplier have a calibrated CMM (coordinate measuring machine)? I have visited shops that claim to do "precision machining" but have nothing more than calipers and a bench micrometer. For parts with tolerances tighter than ±0.05 mm, a CMM is not optional. Ask for the calibration certificate. A CMM that has not been calibrated in 18 months is a table.

Military certifications like GJB9001C (the Chinese military quality standard) indicate a supplier has gone through stricter auditing. That does not mean you need military-certified parts. It means the factory has been audited to a standard that is more demanding than ISO 9001, which gives you extra confidence in their process control.

Stage 3: evaluate technical capability and equipment

Ask the supplier what equipment they run. Not "what can you make?" but "what machines are on your floor?" The answer tells you whether they can actually produce your part. A shop with three VMCs and one lathe is not going to produce 50,000 MIM parts per month. They might broker the order to someone else.

If you need CNC machined parts, ask about machine brands and controller types. A Fanuc-controlled DMG Mori is not the same as a no-name domestic machine. Both can hold tolerance, but the DMG Mori holds it longer with less maintenance. For tight tolerance work (±0.025 mm or better), I want to see Japanese or German machines, or high-end domestic brands with linear guides.

If you need MIM parts, ask about the sintering furnace. Does the supplier own the furnace or outsource sintering? Outsourced sintering is common and not necessarily a problem, but it adds a variable you need to track. The furnace type (batch vs. continuous) affects the density and dimensional consistency of your parts. A continuous furnace gives better batch-to-batch consistency. A batch furnace is fine for lower volumes but can produce more variation between loads.

Ask to see a part similar to yours that they already make. Not a sample from their website. A physical part, with the original drawing, that they ship to an existing customer. If the part has complex features in the same ballpark as yours and the surface finish looks right, you have real evidence of capability. If they can only show you simple cylinders, you are their first complex part. That is fine if the price reflects the risk. It is not fine if they are charging production pricing for a learning curve.

Stage 4: test with a trial order and first article inspection

Never go straight to a production order with a new supplier. I learned this the hard way in 2019 when I trusted a new shop with 5,000 brackets and received parts with the wrong thread pitch. The drawing said M6, the parts had 1/4-20. They had guessed instead of checking, and I had 5,000 unusable parts.

Order a small trial batch first. Five to ten pieces. Specify that you require a first article inspection (FAI) report with dimensional data. A good supplier does this automatically. A supplier who pushes back on an FAI request is a supplier who does not have a quality system, no matter what their ISO certificate says.

When the FAI report arrives, check the actual numbers. Do not just check that the report exists. I have seen FAI reports where every dimension is marked "pass" with no actual measured value. That is a formality, not an inspection. You need to see the nominal, the tolerance, and the measured value for each critical dimension. If the measured value for a ±0.05 mm bore is listed as "0.05," that is not a measurement. That is the tolerance.

Inspect the samples yourself when they arrive. Measure three to five critical dimensions with your own calipers or micrometer. If you do not have measurement tools, send the parts to a local inspection lab. A CMM inspection costs 80 to 200 USD per part. That is cheap insurance against a 50,000-unit production run.

Check the material too. Ask for a material certificate (mill test report, MTR). For 316L stainless steel, the MTR should list the heat number, chemical composition, and mechanical properties. Cross-check the chemistry against the ASTM A240 or ASTM A276 spec. If the carbon content is 0.08 percent and the spec calls for 0.03 percent max, you do not have 316L. You have 316. The supplier may not even know the difference. That is exactly why you check.

Stage 5: assess communication and export experience

Technical capability is necessary but not sufficient. A supplier who cannot communicate will make your project painful even if the parts are good. I would rather work with a B+ factory that answers emails in four hours than an A factory that takes five days to respond.

Test the communication early. Send a drawing with a deliberate DFM question embedded in it. Something like: "This wall is 0.8 mm. Can your process hold this?" A good supplier comes back with a specific answer: "0.8 mm is feasible in MIM but we recommend 1.0 mm for this geometry." A poor supplier says "No problem, we can do it." The specific answer shows they thought about your part. The generic answer shows they did not.

Check whether the supplier has export experience to your region. A supplier who has only shipped domestically may not understand INCOTERMS, packing standards for ocean freight, or CE documentation requirements. Ask for references from customers in your country or region. A supplier with export experience to Europe or North America has already learned the hard lessons about packaging, documentation, and lead time communication.

Pay attention to how they handle bad news. During your trial order, something will go wrong. A tool breaks. A sintering cycle runs hot. The question is not whether problems happen. The question is whether the supplier tells you before or after the ship date. I have worked with suppliers who call the same day a problem occurs and suppliers who wait until the delivery date to mention a two-week delay. The first type is worth keeping. The second type will cost you customers.

Common red flags I have learned to watch for

Here are the patterns that tell me to walk away, no matter how good the pricing looks:

Refusing to provide a business license or factory address. I do not care how good the website looks. No license, no order.

Quoting without seeing a drawing. A supplier who gives you a price before seeing the part is quoting blind. The price will change, or the quality will suffer. Both outcomes cost you.

Claiming every certification under the sun. A mid-size shop claiming ISO 9001, IATF 16949, AS9100, and ISO 13485 all at once is either exceptional or lying. Most shops specialize. A shop with ISO 9001 and GJB9001C is believable for automotive and industrial parts. A shop with everything is likely a trading company listing every cert held by any partner factory.

Pushing for 100 percent upfront payment. Standard terms for a new relationship are 30/70 or 50/50. A supplier who insists on 100 percent upfront with no trial order and no history is a supplier who has been burned before, or a supplier who does not intend to deliver. Either way, the risk is on you.

Slow response to technical questions but fast response to "when do you pay." If the supplier replies to payment questions in 30 minutes but takes three days to answer a tolerance question, their priority is revenue, not engineering. That is fine for a commodity part. It is dangerous for anything with a tight tolerance or a new design.

The cost of skipping vetting

I want to be concrete about what happens when you skip these steps. In 2021, I worked with a supplier who had a good website, responded quickly, and quoted 20 percent below the next bidder. I skipped the factory audit because the timeline was tight. The trial order looked acceptable. The production order of 20,000 parts arrived with 40 percent out of tolerance on a critical bore dimension. The supplier disputed the inspection results. The dispute took six weeks. I lost the customer. The 20 percent savings turned into a total loss.

The vetting process I described above takes two to four weeks. It costs a few hundred dollars in sample orders and inspection fees. Compare that to the cost of a failed production run. The math is simple. The only question is whether you do the work before the PO or after the problem.

Checklist: 12 questions to ask before placing an order

1. Can you send me a copy of your business license?

2. What is your registered company name and legal representative?

3. What quality certifications do you hold? Can I see the certificate numbers?

4. Do you own the factory? What is the factory address?

5. What machines do you have on the floor? (Brand and model for critical equipment)

6. Can you show me a part similar to mine that you already produce?

7. Do you have a calibrated CMM? When was it last calibrated?

8. Can you provide an FAI report with measured values for the trial order?

9. Can you provide a material certificate (MTR) for the material I need?

10. What are your standard payment terms for a new customer?

11. Do you have export experience to my country? Can you provide a reference?

12. What is your standard lead time for a trial order? For a production order?

If a supplier answers all twelve questions with specific, verifiable information, you have a strong candidate. If they hedge on three or more, keep looking. The FAQ page on our site covers additional questions about our own processes and capabilities if you want to see how a vetted supplier should respond.