Guides for buyers commissioning custom parts from Chinese machine shops: sheet metal fabrication, CNC machining, and surface finishing. We focus on the specification choices and documentation that separate serious manufacturers from resellers.
Verified guides are published as they complete. Every guide below is dated and names the official or standards-body source behind each figure.
The two GB profile families the national register actually separates, the tolerance and finish standards a specification has to name, the edition numbers already withdrawn, and why the obvious Chinese search term returns nothing.
Read the guide →The GB standards for hot-rolled H-beams, structural plates and bolted connections — and why a third of the family is already abolished.
Read the guide →The GB families behind quenching, tempering, carburising and nitriding — and why the obvious Chinese search term returns mostly ceramics.
Read the guide →The four jobs the register separates — procedure qualification, the procedure specification, operator skill and weld examination — and why half the welding records are pipes.
Read the guide →The lost-wax process step by step, which ISO and ASTM standards govern investment castings, how tolerance grades and machining allowances are indicated, and the enquiry fields that make quotations comparable.
Read the guide →The ISO and UL standards behind tolerances and material ratings, how to divide the work between your drawing and the supplier, and the enquiry fields that make quotations comparable.
Read the guide →How a general-tolerance callout and per-feature limits divide the work between you and the supplier, how to read and write Ra and Rz surface symbols, the RFQ details that make quotations comparable, and how incoming inspection is actually verified.
Read the guide →Hot-chamber or cold-chamber by alloy, what ASTM B85/B85M and ASTM B94 fix, what ISO 8062-3 covers and what it leaves to the drawing, and how to specify porosity and integrity requirements.
Read the guide →What separates 304 from 316 stainless, where 6061 and 7075 aluminium fit, and how to write grade, temper and inspection-document requirements on a drawing so quotes come back comparable.
Read the guide →Design for the tooling: minimum bend radius and flange checks, ISO 2768 / ISO 13920 / ISO 9013 on the drawing, material and finish standards, and the eight design rules that prevent rework.
Read the guide →3-, 4- and 5-axis milling, turning and EDM; material grades and their standards; general tolerances, GD&T and surface texture; finishing options; eight DFM rules; and how to verify a Chinese machine shop before you order.
Read the guide →Anodizing, plating, powder coating, and passivation: what each process affects, and how cost, lead time, and compliance requirements interact.
Read the guide →Before you quote. Regardless of process, prepare: a clear drawing (native or neutral CAD plus PDF), material specification, critical tolerances, target quantity, and finishing requirements. Every guide in this section will explain how suppliers use these inputs — and what happens when they are missing.
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