Overview
EN ISO 17450-3:2016 (ISO 17450-3:2016) is a fundamental Geometrical Product Specification (GPS) standard published by CEN/ISO. It provides default definitions for extracted features (integral or derived) of workpieces that are used as toleranced features in GPS specifications - covering dimensional, geometrical and surface texture characteristics. This part of ISO 17450 defines the default geometrical features and decision rules used when specifying and verifying toleranced features.
Key topics and requirements
- Default feature definitions: Provides standardized definitions for integral features, median features and elementary toleranced features, ensuring consistent interpretation of toleranced geometry.
- Extracted features: Describes how extracted integral features are derived from real workpiece geometry (point extraction, sectioning and intersection rules).
- Opposing point pair and median concepts: Defines terms such as opposing point pair, median point/line/surface and median centre used to calculate sizes and positions for features of size.
- Rules for establishing geometrical features: Specifies default rules for forming section lines, intersection planes (full or half planes), boundaries and how a complete extracted integral feature relates to elementary toleranced features.
- Relationship to GPS characteristics: Explains how toleranced features link to GPS characteristics (intrinsic, location and orientation) used in dimensional and geometrical specifications.
- Verification implications: Clarifies default assumptions used in inspection and verification when infinite point extraction is not possible in practice.
Applications and users
EN ISO 17450-3 is used wherever consistent interpretation of toleranced features is required:
- Mechanical design and CAD/CAM: defining and communicating toleranced geometry in drawings and models.
- Manufacturing and process engineering: setting and interpreting feature tolerances for machining, assembly and production control.
- Metrology and QA/inspection laboratories: establishing how measured data map to extracted and toleranced features for verification and acceptance.
- Standards bodies and technical committees: harmonizing terminology and rules across GPS standards and regulatory documents.
Typical users: mechanical designers, metrologists, inspection engineers, quality managers, calibration laboratories and standards developers seeking consistent GPS practice.
Related standards
Keywords: EN ISO 17450-3:2016, ISO 17450-3, Geometrical Product Specifications, GPS, toleranced features, extracted features, median feature, opposing point pair, dimensional specification, metrology.
