How to Evaluate a Chinese Sheet Metal Fabrication Supplier: 12 Checks

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Twelve things to check, and what a good answer looks like

Sourcing sheet metal fabrication from China is not difficult. Sourcing it well is, because most of the information you need is not in the quotation.

This checklist covers the twelve points that decide whether a project runs smoothly, in the order you will encounter them. Each one is checkable before you send a deposit, and each entry says what a credible answer sounds like rather than what the supplier should claim.

Use it against any supplier, including us. We have written it so that you can mark us down where we fall short.

1. What happened when you sent the drawing

Send one real part, with a real tolerance, and watch what comes back.

A strong response asks a question about the drawing. Something with a consequence: which surface the datum is on, whether a bend relief is intended, whether a 0.8 mm radius on 2 mm stainless is deliberate. A weak response is a price.

Good answer: a question that shows the drawing was read before the number was produced.

2. Whether the quote contains a process route

Laser cut, deburr, form, weld, finish, inspect — with a tolerance stated at each stage.

The route is what makes a quote usable. It tells you which step costs the money, so you can change a variable and predict the effect. A price without a route cannot be negotiated intelligently, because you do not know what you would be trading away.

Good answer: a route short enough to read, specific about the process chosen and why.

3. Whether tolerance capability is stated as a number

Not “high precision”. Actual figures, and the process they belong to.

Laser cutting, forming and machining hold different tolerances, and a supplier who gives one figure for all three does not understand their own process. On our routes, laser cutting holds about ±0.05 mm, forming about ±0.1 mm, and five-axis machining ±0.005 mm on the features that require it, verified on a CMM with a stated measuring accuracy of ±0.002 mm.

Good answer: a different figure per process, with the measuring method named.

4. What inspection documentation comes with the batch

Ask what physically ships with the parts, not what the quality system contains.

“Measured values, not a pass stamp” is the standard to hold them to. That means a dimensional report against the drawing’s nominal and tolerance, a first article inspection report on production runs, material certification traceable to the heat, and coating thickness readings where a finish has been applied.

Good answer: a list of documents, offered without being asked twice, and a sample report from a completed job produced quickly.

5. The certification registration number

Ask for the number, not the certificate image, then look up the issuing body and the scope.

ISO 9001:2015 is the baseline and most established factories hold it. Automotive work needs IATF 16949. Environmental management is ISO 14001. If your programme requires AS9100, NADCAP or ISO 13485, ask directly, and treat a vague answer as a no.

Good answer: a number you can verify, and a clear statement of what is not held.

6. Material traceability

The question is whether the steel in your part can be traced back to a heat number and a mill certificate.

For regulated or safety-relevant parts this is not optional. Ask for EN 10204 3.1 certification, and ask whether the certificate is issued per batch or copied from the mill’s general paperwork.

Good answer: per-batch traceability, with the certificate referenced on the inspection documents.

7. Who owns the tooling

If your part needs a die, the die is a substantial asset and its ownership matters.

Ask who owns the tool, where it is stored, and what happens to it if you move your business. A supplier who cannot answer this cleanly may not have the tool in their building.

Good answer: the tool is owned by the customer or transferable on request, and its location is stated.

8. The capacity limit, stated unprompted

Every plant has a maximum part size, a maximum thickness and a press tonnage ceiling. Ask for all three, then ask what happens if the job exceeds them.

A supplier who tells you the limit before you hit it is managing your project. A supplier who discovers the limit during production is managing their own problem at your expense.

Good answer: numbers, and a straight answer about what they do when a job is outside them.

9. The minimum order quantity, and the reasoning behind it

Ask what the minimum is, and then ask why it is set there.

MOQ is usually a coordination cost, not a machine cost. A factory with the tool room and the press in the same building can absorb a small order; a firm passing work to third parties cannot. If the answer to “why” is vague, the number was probably not calculated by the people making the part.

Good answer: no minimum, or a minimum with an explanation that references tooling, setup or material purchase.

10. Export and delivery competence

Ask which Incoterms they normally quote and who handles the customs documentation.

A supplier who quotes FOB without being able to explain the handover point, or who cannot say what duties the destination country will apply, is going to leave that work with you. Our own position is that duties are set by the destination country and paid by the buyer unless the terms say otherwise, and that Incoterms should be agreed during quoting rather than assumed. Air express runs 3 to 7 days, sea freight 15 to 30.

Good answer: the Incoterm named and understood, and an honest statement about what the buyer pays on arrival.

11. Who answers the technical questions

Put an engineering question into the first three emails and see who replies.

In a plant, the answer carries a reason: this radius will crack on 316 at that thickness; this hole is too close to the bend line; this flat pattern will not close. In an intermediary, the question is forwarded and the reply comes back later and thinner.

Good answer: a process reason attached to the answer, and sometimes a recommendation to change the design.

12. What they say they cannot do

Ask last, and listen carefully. It is the most informative question on the list.

A supplier who describes their limits without hesitation is telling you they know their process. A supplier who claims everything is telling you they sub-contract, which is not disqualifying — but you should then ask who to.

Good answer: a specific list, offered unprompted. We do not hold AS9100, NADCAP or ISO 13485, and we say so on the pages where it matters rather than only when asked.

The checklist as a scoring sheet

#	Check	Credible answer	Warning sign
1	Response to your drawing	Asks a question with a consequence	Sends only a price
2	Process route in the quote	Named stages with tolerances	A number, no route
3	Tolerance capability	A different figure per process	One figure for everything
4	Documents in the box	Measured values, per batch	A pass stamp
5	Certification	Registration number, verifiable	A logo image
6	Material traceability	EN 10204 3.1, per batch	Copied mill paperwork
7	Tooling ownership	Stated, and transferable	Deflected question
8	Capacity limits	Volunteered numbers	Discovered in production
9	Minimum order	Explained by tooling or setup	High, unexplained
10	Incoterms and duties	Named, understood, buyer cost stated	Vague on arrival costs
11	Who answers engineering	An engineer, with reasons	Forwarded and delayed
12	Stated limits	A specific list	Claims every process

Nine or more credible answers is a supplier worth a trial order. Fewer than six, and the questions were probably answered by somebody who had to go and ask.

Two related pages go deeper on the two checks buyers find hardest to make from outside: telling a factory from a trading company, and comparing platform models with a single plant.

Key facts

Quote turnaround	24 hours, including a design-for-manufacture review
Sample lead time	7 days typical
Production lead time	20 to 30 business days after sample approval
Minimum order quantity	None
Typical tolerances	Laser cutting ±0.05 mm, forming ±0.1 mm, five-axis machining ±0.005 mm where required
Quality management	ISO 9001:2015, registration 34025Q30296R0S; IATF 16949; ISO 14001
Not held	AS9100, NADCAP, ISO 13485
Documents shipped	CMM report, first article inspection report, EN 10204 3.1 certificate, finish readings

Frequently asked questions

What should I ask a Chinese sheet metal supplier before ordering?

Ask what inspection documents ship with the batch, for the certification registration number, whether material is traceable per heat, who owns the tooling, what the capacity limits are, and what the supplier cannot make. These five answers separate a factory that controls its process from one that is passing your work along.

How do I check whether a supplier can actually hold my tolerances?

Ask for a different figure per process rather than one headline number, then ask how it is measured. Laser cutting, forming and machining hold different tolerances, and a credible supplier names the process and the measuring equipment. A single figure covering everything suggests the number was not derived from the machines that will run the job.

Is a low price a warning sign when sourcing metal parts from China?

Not by itself, but an unexplained low price is. Ask what is not included: material certification, finishing, inspection documentation, or packing. A price that leaves those out is not a lower price, it is a narrower scope, and the difference usually appears after the parts have shipped.

What is the most informative single question to ask a potential supplier?

Ask what they cannot make. A factory knows its limits precisely and will describe them, including certifications it does not hold. A supplier who claims every process is almost certainly sub-contracting, which is not disqualifying but does mean you need to know who is actually making the part.

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