Guides

Sourcing guides for precision components

Technical reference material written for buyers, not for search engines. Each guide answers one question a purchasing manager actually asks before placing an order in China.

• Supplier vetting

  How to verify a CNC machining factory in China

  A practical checklist for vetting a Chinese CNC factory: business licence checks, machine lists, sample parts, video calls and the five red flags that mean walk away.

• Engineering reference

  CNC tolerance chart: metric to inch conversion

  Convert CNC machining tolerances between mm and inch, understand IT grades, and know which tolerances cost money. Includes a reference table for common fits.

• Materials

  6061 vs 7075 aluminium for CNC machining

  Practical differences between 6061-T6 and 7075-T6 for CNC parts: machinability, strength, anodising, cost and corrosion. When 7075 is worth the premium.

• Quality control

  AQL inspection levels explained

  How AQL sampling works for machined parts: General Inspection Levels I, II and III, the 1.0 vs 2.5 vs 4.0 defect thresholds, and how to read an inspection report.

• Quality control

  Why CNC parts fail inspection

  The nine defects that cause most CNC machining rejections — burrs, chatter, tool marks, thread damage, out-of-tolerance bores — and the process fix for each.

• Costing

  How much does CNC machining cost in China?

  A line-by-line breakdown of CNC machining cost in China: material, setup, machine time, finishing, tooling and agent commission. Includes typical 2026 price ranges.