Overview
SIST EN ISO 14405-1:2025 (ISO 14405-1:2025) - Geometrical product specifications (GPS) - Dimensional tolerancing - Part 1: Linear sizes provides the rules and graphical notation for indicating and specifying linear size characteristics on engineering drawings and related documentation. Adopted as EN ISO 14405-1:2025 and published by SIST, this third edition updates and clarifies how linear sizes are specified for features such as cylinders, spheres and two parallel opposite planes, in accordance with the GPS framework.
Key topics and technical requirements
- Scope and applicability: Establishes how to indicate linear sizes and the default specification operator (see ISO 17450-2) and defines a special specification operator for linear sizes. It does not prescribe relationships between function/use and size characteristics.
- Applicable features: Explicitly covers linear-size features defined in ISO 17450-1 - cylinders, spheres and two parallel opposite planes.
- Syntax and graphical rules: Introduces a structured syntax with multiple indication areas and defined sequences of specification elements for each area. Graphical rules and proportions for symbols are normative.
- Stacked specifications: Permits and defines rules for stacking linear size specifications (useful when combining tolerances or stacking with geometric tolerances).
- Specification operators and modifiers: Clarifies the ISO default operator and supports drawing-specific defaults; introduces notation changes (e.g., addition of k×/n× for stacking with geometric specifications; removal of “/0” in favor of the ACS modifier).
- Specific cases and annexes: Normative annexes cover specialized uses (e.g., linear size on circles of cones, torus sections, parallel lines); informative annexes discuss data handling with statistical sizes and legacy practices.
- Additional requirements: Rules for indication of the toleranced feature, envelope requirements for internal/external features, filtration, and direction feature are included.
Practical applications and users
- Who uses it: Mechanical designers, CAD/CAM engineers, manufacturing engineers, metrologists, quality/control engineers, technical drafters, and standards committees.
- Where it applies: Product design and drawings, tolerance specification on assembly drawings, inspection and metrology procedures, CAD model and drawing annotation, supplier quality requirements, and interchange of manufacturing data across firms and borders.
- Benefits: Consistent, unambiguous linear size specification; improved interoperability between design, manufacturing and inspection; clearer stacking and combination rules with geometric tolerances.
Related standards
Keywords: ISO 14405-1, SIST EN ISO 14405-1:2025, linear sizes, dimensional tolerancing, GPS, cylinders, spheres, tolerance specification, metrology.
