How do I verify an ISO 9001 certificate from a Chinese fastener supplier?

Ask for the certificate number and issuing body, then check them with that body. A genuine certificate has a number, a scope statement covering the products you buy, an expiry date and an IAF code.

What should I check before ordering custom screws from China?

Eight things: the verifiable certificate number, who owns the tooling, how the finish is specified (salt spray hours, not a coating name), baking after plating on high-strength parts, how straightness and thread run-out are measured on long parts, whether the supplier will say when cold heading is the wrong route, what the sample actually proves versus what is checked per batch, and how they analyse a field failure.

Is cold heading cheaper than machining for custom fasteners?

Above roughly 20,000 pieces, cold heading is usually well below machining because the die cost is amortised and almost no material is wasted. Below that volume, or where the geometry needs a bore or a very tight tolerance, turning is the better route.

Before you order custom fasteners from China: eight things to verify

1. Can you verify the certificate, or only see a picture of it?

Ask for the certificate number and the issuing body, then look it up yourself. A real ISO 9001 certificate has a number, a scope statement, an expiry date and an IAF code — and the body that issued it will confirm all four.

Good answer: a number you can check in thirty seconds. Red flag: a scanned image with no number, or a scope that does not mention the products you are buying.

2. Who owns the die?

On a cold-headed part, the die is most of the upfront cost. Ask whether the tooling is cut in-house or subcontracted, and who holds it if you move. A supplier who owns the dies can quote a revision without waiting for a third party — and can tell you honestly whether an existing die already fits your part.

Good answer: dies held on site, with a count of existing dies and a statement about ownership. Red flag: every quote includes a tooling charge, even for a standard shape.

3. What is the finish specified as — a name or a test?

'Zinc plated' is not a specification. Ask for the salt spray requirement in hours to red rust, and the coating system that achieves it. Zinc with clear passivation and zinc-nickel differ by a factor of ten in corrosion performance and look identical on a drawing.

Good answer: hours to red rust, measurement method (XRF), and a report per batch. Red flag: 'we always do good zinc'.

4. Above class 10.9, is there baking after plating?

Acid cleaning and plating can drive hydrogen into high-strength steel. Parts above roughly property class 10.9 should be baked after plating, and the supplier should say so without being asked. This is one of the first things an automotive auditor checks.

Good answer: a stated baking step with time and temperature. Red flag: silence, or 'our plating partner handles it' with no detail.

5. How is straightness measured on a long part?

On a 300 mm screw, straightness at both ends tells you nothing — the bow is in the middle. Ask how it is measured over the full length, and how thread run-out is referenced: against the screw axis, or against the head.

Good answer: full-length measurement, run-out referenced to the axis. Red flag: 'it comes out straight'.

6. Will they tell you when your part should not be cold-headed?

The most useful answer a supplier can give is that your drawing belongs on a lathe, or that a design change removes a machining step. A shop that only heads will quote heading for everything; a shop that only turns will quote turning.

Good answer: a process route with reasons, including the cases where heading loses. Red flag: every part is a heading part.

7. What does the sample actually prove?

A sample proves the geometry. It does not prove that batch ten will match batch one, or that the plating thickness holds across a barrel. Ask what is measured on the sample and what is measured per batch in production — they are usually different lists.

Good answer: a first-article report plus a stated patrol inspection. Red flag: a sample with no dimensional report.

8. What happens when a part fails in the field?

The answer tells you whether they think in terms of mechanism. Plating thickness, edge condition, concentricity, heat treatment — a supplier who starts from the failure mode can usually name the cause from a photograph and a batch number.

Good answer: a failure hypothesis and the measurements that would confirm it. Red flag: 'our quality is very good'.

The checklist in one table

Check	Good answer	Red flag
Certificate	Number, scope, expiry, issuing body	An image with no number
Tooling	Dies cut in-house, ownership stated	Tooling charge on every quote
Finish	Hours to red rust + measurement method	'Good quality zinc'
High-strength parts	Baking after plating, time and temperature	Silence
Long parts	Straightness over full length, run-out to axis	'Comes out straight'
Process route	Says when heading is wrong for the part	Every part is a heading part
Samples	First-article report, patrol inspection defined	Sample with no report
Failures	Starts from the failure mechanism	'Our quality is very good'

The pattern behind all eight

A supplier who can answer these is a supplier who measures things. The answers matter less than the fact that they exist — a factory that knows its salt spray hours, its die ownership and its failure modes will also know when your part is about to go wrong.

Cold heading vs machining → Specifying a finish → Seven signature parts →