Before you contact a factory: verify the three basics
Most sourcing problems start before the first email. Verify three things about any Chinese CNC supplier before sending a drawing: whether they are a real manufacturer rather than a trading company, whether they own their inspection equipment, and whether they hold a quality certification such as ISO 9001. A direct manufacturer answers with specifics — machine brands, CMM model, headcount — while a trader answers with generic promises.
How to check a factory's real machining capability
Capability is proven by what the shop can hold, not by what it claims. Ask for the standard tolerance on critical dimensions, the surface finishes they run as standard, the materials they machine in-house, and how they verify parts. A serious shop holds ±0.005 mm on critical features, runs Ra 0.4–0.8 μm as standard, machines aluminum, stainless, titanium and engineering plastics in-house, and verifies on a CMM with a free FAI report on the first order.
Questions that separate real factories from resellers
Ask six questions and listen to how they answer: What CMM do you inspect on and when was it last calibrated? How many dedicated QC staff do you employ, separate from machinists? Do you provide material certificates with each batch? Is any work subcontracted, and if so which process? Can you machine titanium and engineering plastics in-house? Do you include a first-article inspection report? Factories answer with numbers and names; resellers answer with assurances.
How to evaluate the quality system
Quality in China is a system, not a promise. Look for ISO 9001 certification, in-house CMM inspection, first-article inspection (FAI) on the first batch, measured values on critical dimensions, and material traceability with heat numbers. Ask for a sample FAI report and a photo of the CMM with its calibration certificate — any factory that has been exporting for years can produce both in minutes.
Red flags to walk away from
No certification, no in-house inspection, instant quotes without asking a single technical question, no material traceability, vague answers about subcontracting, or a photo gallery that looks like it was copied from another company. The most expensive mistake is not a slightly higher price — it is a beautiful first article followed by drifting quality on later batches because the shop outsourced your order.
How to protect your design and IP
Send drawings with customer-specific information removed, sign an NDA where the project warrants it, and use DFM feedback as a test of seriousness — a real shop reviews manufacturability and suggests cost-saving changes before cutting metal, without publishing anything about your project. A factory that discusses your part like an engineering problem, not a sales opportunity, is the one you can build a long relationship with.
Frequently Asked Questions
What should I verify before contacting a CNC factory in China?
Three things: whether they are a real manufacturer (not a trading company), whether they have their own inspection equipment, and whether they hold a quality certification such as ISO 9001. Ask for the factory name, the machine list, and the CMM model — a real shop answers with specifics.
How do I know if a Chinese CNC factory is actually capable of my tolerance?
Ask what tolerance they hold as a standard, what CMM they inspect on, and whether a first-article report is included. A shop that holds ±0.005 mm on critical dimensions, inspects on a CMM and includes free FAI on the first order is showing real capability, not quoting marketing numbers.
What questions separate a serious factory from a trading company?
Ask about machine brands and counts, CMM calibration certificates, how many dedicated QC staff they employ, whether material certificates are provided with each batch, and whether any work is subcontracted. Trading companies go quiet on specifics; factories answer directly.
What red flags should make me walk away from a supplier?
No quality certification, no in-house inspection equipment, instant quotes with no technical questions, no material traceability, and vague answers about subcontracting. Also be careful with shops that only show photos of other factories' machines.
How do I protect my design when sending drawings to a Chinese supplier?
Send drawings with customer-specific information removed, sign an NDA where the project warrants it, and use DFM feedback as a test — a serious shop reviews manufacturability and suggests cost-saving changes before cutting metal, without publishing anything about your project.
Do Chinese CNC factories provide CMM reports and material certificates?
Yes — this is standard for export work. Expect CMM FAI reports on the first article, measured values on critical dimensions, and material certificates (MTRs) with each batch when specified. Ask for sample reports before placing the order.