ISO system of limits and fits; Part I : General, tolerances and deviations

This document establishes a fundamental framework for the system of limits and fits used globally in mechanical engineering and manufacturing. It defines the theoretical basis for tolerances and deviations, enabling the interchangeability of parts across different production environments and national boundaries. The approach outlined here organizes tolerance classes into standardized sequences, allowing engineers to specify appropriate fits based on functional requirements such as clearance, transition, or interference. By providing a unified method for defining allowable variations in dimensions, this system supports the design and assembly processes in industries ranging from automotive to aerospace. The content focuses on general principles rather than specific applications or case studies. It serves as a foundational reference for subsequent specialized standards that address detailed applications in various fields. The methodology presented ensures consistency in dimensional specifications, facilitating efficient communication between designers, manufacturers, and inspectors without requiring direct reference to the originating organization or the exact historical date of its adoption.