GB/T 1800.1-2009

This standard defines the fundamental principles for specifying and interpreting dimensional tolerances, deviations, and fits in mechanical engineering. It is applied in the design, manufacturing, and quality inspection of interchangeable parts, such as shafts and holes, to ensure consistent assembly and performance across industries like automotive, aerospace, and machinery. The standard provides the basis for selecting tolerance classes and calculating fit types (clearance, transition, interference) in technical drawings and production specifications.