Overview
EN 22768-1:1993 (identical with ISO 2768-1:1989) defines general tolerances for linear and angular dimensions that have no individual tolerance indications on drawings. Its purpose is to simplify drawing indications and to provide default tolerance rules for parts produced by metal removal or formed from sheet metal. The part contains three tables of permissible deviations, an informative annex explaining the concepts behind general tolerancing, and guidance on how to declare the tolerancing on drawings.
Key topics and requirements
- Scope: Applies to linear dimensions (external/internal sizes, diameters, radii, distances, chamfers) and angular dimensions where no specific tolerance is shown. It excludes auxiliary dimensions in brackets and theoretically exact dimensions.
- Tolerance classes: Defines four general tolerance classes - fine, medium, coarse, and very coarse - aligned to customary workshop accuracy. Designers select the class appropriate to function and manufacturing capability.
- Reference on drawings: To apply the standard, drawings must state the reference (e.g., “ISO 2768-1”) and the chosen tolerance class in or near the title block.
- Tables and annex: Contains three normative tables (linear dimensions, broken edges such as external radii and chamfers, and angular deviations) and an informative Annex A describing the rationale and practical use of general tolerances.
- Non-rejection rule: Exceeding a general tolerance does not automatically require rejection if the part’s function is not impaired - inspection decisions should consider functional fit.
- Interaction with other standards: If other general tolerance standards apply (e.g., for castings), those must be referenced instead.
Practical applications
- Use EN 22768-1:1993 for production drawings where many dimensions do not require tight individual tolerances, such as:
- Machined components produced by metal removal
- Sheet-metal parts and assemblies
- General mechanical parts where standard workshop accuracy suffices
- Benefits include clearer drawings, reduced dimension-by-dimension tolerancing work, easier supplier negotiations, and lower inspection burden for non-critical features.
Who should use this standard
- Design engineers and draughtsmen preparing production drawings
- Manufacturing engineers and shop floor supervisors determining process capability
- Quality and inspection teams for sampling and acceptance decisions
- Purchasing and subcontracting specialists negotiating production orders
Related standards
- ISO 2768-2: Geometrical tolerances for features without individual indications
- ISO 8015: Fundamental tolerancing principle
- ISO 8062: Dimensional tolerances for castings (parallel guidance where applicable)
Keywords: EN 22768-1:1993, ISO 2768-1:1989, general tolerances, linear and angular dimensions, tolerance classes, drawing indications, sheet metal, machined parts.
