GB/T 1800.4-1999

This standard provides the specific numerical tables for standard tolerance grades and limit deviations for holes and shafts, as defined by the ISO-based limit and fit system. It is applied in mechanical engineering and manufacturing industries to define the allowable variation in dimensions for mating parts, ensuring consistent assembly and interchangeability in products like automotive components, machine tools, and industrial equipment. The tables are used by designers and quality inspectors to select appropriate fits (e.g., clearance, transition, or interference) during the design and production of precision-engineered assemblies.