Most sourcing guides tell you to ask for a catalogue, a price list and a factory audit. In practice, the answers that separate a workshop from a real supplier come from six much smaller questions. Here is what each one is really testing, and how a credible answer sounds.
1. "Which machine will my part run on?"
This is the question that decides your unit price, and almost nobody asks it first.
A turned part with an outer diameter of 3 mm and one of 10 mm are not the same job even when the material and drawing look similar. Swiss-type lathes hold the bar in a guide bushing and feed it forward as they cut, which is why they stay stable on small diameters and long length-to-diameter ratios — roughly the Ø2–20 mm range.
If a supplier quotes both parts off the same machine without mentioning the difference, either the shop is over-equipped or the quote is a guess.
2. "What is the tolerance, and where does the cost step change?"
Tolerance is not a single number that gets stamped on a quote. Ask which dimensions are actually critical, and ask what happens to the price if one of them tightens.
A supplier who answers "all dimensions ±0.005 mm" without asking which ones matter is not being precise — they are avoiding the conversation. In our own shop the working tolerance is ±0.005 mm, with tighter bands quoted as "or better", and anything looser is quoted against ISO 2768-m rather than an invented number.
3. "What will you scrap to get the first good part?"
Small parts fail faster. Tools break, chips weld, dimensions drift. On a Ø3 part, the first-article tuning can consume more material than the first delivery.
A real answer includes an estimate of that scrap, not a promise that there won't be any. If the number is zero, the risk has simply been moved into the unit price or into a later delivery date.
4. "How will you measure it?"
Calipers do not measure roundness or coaxiality on a 3 mm pin. Neither does a visual check. Parts that size usually go to a profile projector or a vision system, and inspection time can exceed machining time on a small batch.
Ask what the inspection plan is for the specific features on your drawing. If the answer is "we check every part", the next question is with what.
5. "How is my 50 pieces scheduled next to someone's 50,000?"
Set-up time is the fixed cost that gets divided by your batch size. A quote for 1 piece and a quote for 5,000 pieces of the same drawing can differ several-fold, and it is not because the machine runs faster.
Ask whether small batches wait for a gap in a larger run or get their own set-up. The answer tells you more about lead time reliability than any delivery promise.
6. "Who actually owns the tools and the program?"
For repeat orders this matters more than price. If the fixture and the program belong to the supplier, switching later means paying for them again — which is fine, as long as you know it on day one.
What the answers look like from our side
We are CHX Metal (深圳市常合鑫精密五金有限公司), a precision hardware shop in Bao'an, Shenzhen. Thirteen years in, 220 machines on the floor — 100 machining centres, 50 CNC lathes and 70 Tsugami Swiss-type lathes — turning out small parts for automation equipment, optical modules and robotics customers. Monthly capacity is around 5 million pieces, MOQ is one piece, sampling runs 3–7 days and production 7–15 days.
That is not an argument that we are the right shop for your part. It is the set of answers we would give to the six questions above, written down so you can compare them against whoever else you are talking to.
A buyer rarely needs a supplier to be the biggest. They need the answers to be specific enough to check.
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