How to verify a CNC machining factory in China
Most buyers lose money in China not because the factory is dishonest, but because they never confirmed it was a factory at all. This is the check sequence I use before accepting a new supplier for a client order.
Most buyers lose money in China not because the factory is dishonest, but because they never confirmed it was a factory at all. A trading company with a nice website can quote you a machined part, subcontract it to an unknown workshop, and disappear the moment a tolerance is questioned.
This is the verification sequence I run before accepting a new supplier for a client order. It takes about a week and costs almost nothing.
Step 1: Check the business licence, and read the registered scope
Every Chinese company has a unified social credit code, an 18-character identifier you can look up on the National Enterprise Credit Information Publicity System (gsxt.gov.cn). Ask for a photo of the licence and check three things:
- Registered capital. Under RMB 1 million usually means a very small operation. It is not disqualifying, but it sets your expectations.
- Business scope. It must include machining, casting or the relevant manufacturing activity. A company whose scope is only "trade and import/export" is a trader, not a factory.
- Established date. A company registered 18 months ago has no long production history, whatever its website says.
Watch for: a licence whose registered address is a room in an office building. Machining needs floor space, power capacity and usually a workshop address outside the city centre.
Step 2: Ask for the machine list, then ask for photos of the nameplates
A credible machining factory will list its equipment without hesitation: machine type, brand, axis count, work envelope. What separates a real factory from a trader is that the factory can send you a photo of the machine nameplate with the serial number visible.
For parts under 0.05 mm tolerance, look specifically for:
- CNC vertical machining centres with the controller brand stated (Fanuc, Mitsubishi, Siemens)
- A 3D CMM — not just calipers and a height gauge
- Surface roughness testers if the drawing calls out Ra values
- Heat treatment either in-house or a named, consistent subcontractor
Step 3: Force a video call with the machine running
This is the single most effective check, and almost nobody does it. Ask for a live video call, unannounced, during working hours. Then ask them to walk to a machine and show you the part being cut.
A real factory will do this in two minutes. A trader will reschedule, claim the workshop is "in another city", or show you a prerecorded video. All three answers are the same answer.
Step 4: Order a sample from a different part number
Never approve a factory using the part you actually need. Send a small, low-cost variant — a simplified version of your part, or an unrelated simple bracket — and evaluate the full cycle: quotation speed, drawing feedback, first-article report, packaging quality.
The packaging is more informative than the part. A factory that ships a sample in a bag with no oil paper, no desiccant and no label is telling you how it will ship your production order.
Step 5: Ask what they cannot do
A good factory knows its limits. Ask directly: what tolerances do you struggle with, what materials do you not stock, what would you subcontract?
A factory that claims to do everything perfectly is either inexperienced or planning to subcontract the difficult half of your order to someone you have never met.
The five red flags
| Red flag | What it usually means |
|---|---|
| Will not give a factory address | Trading company, or a workshop with no formal registration |
| Quote is exactly 30–40% below every other quote | They have not read the drawing, or they intend to substitute material |
| Refuses a sample order, only accepts bulk | No confidence in first-article capability |
| Asks for full payment before production | Cash flow problem; your order funds someone else's project |
| Communicates only through a sales rep who "will check with the engineer" | You will never reach the person who actually makes the decision about your tolerance |
What to do when you cannot visit
Most overseas buyers cannot fly to Shenzhen for a two-hour factory visit. That is the gap a local agent fills — not by promising the factory is good, but by standing on the floor and sending you the video that proves it.
If you are verifying a supplier yourself, the sequence above is enough to eliminate the obvious bad actors. It will not tell you whether the factory can hold your specific tolerance on your specific material — only a first-article report does that.
Need this checked on your own part?
Send the drawing and I will review the specification before it reaches a factory, and tell you where it is likely to be misread.
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