Overview
EN ISO 21920-3:2022 (ISO 21920-3:2021) is the GPS (Geometrical Product Specification) standard that defines the complete specification operator for surface texture evaluated by profile methods. It establishes the default decision rules, setting classes and attribute values required to turn a surface-texture indication on a drawing or data sheet into an unambiguous measurement and acceptance procedure.
This part of ISO 21920 is a general GPS standard (chain link C) and replaces ISO 4288. It standardizes how profile surface texture specifications are interpreted, measured and reported for engineering, inspection and quality control.
Key topics and technical requirements
- Scope and normative references: integrates with ISO 21920-1 (indication) and ISO 21920-2 (terms & parameters) and references filtration standards (ISO 16610-21, ISO 16610-31).
- Complete specification operator: defines how a drawing indication becomes a full measurement specification, including filtration, evaluation length, acceptance rules and feature handling.
- Default settings and setting classes (Scn): introduces setting classes (Sc1–Sc5) and rules for default settings based on the drawing indication or specified tolerances.
- Default attribute values: provides default attributes and units for common profile parameters (height, spatial, hybrid, material-ratio, volume and feature parameters) defined in ISO 21920-2.
- Tolerance acceptance rules: adopts the maximum tolerance acceptance rule as the default; provides guidance for upper, lower and bilateral tolerances.
- Profile position and defects: by default, surface defects are considered part of the specified surface when determining profile position.
- Informative annexes: guidance on determining specification operators, worked examples, relation to the GPS matrix model and changes from ISO 4288.
Practical applications
- Standardizes how to define, measure and accept surface texture (profile) in engineering drawings, reducing ambiguity between designers, manufacturers and inspection labs.
- Used by:
- Metrology and quality engineers defining inspection procedures
- Manufacturing and process engineers controlling surface finish
- Calibration and test laboratories implementing measurement protocols
- CAD/PLM teams and drawing authors who need robust surface-specification rules
- Instrument suppliers implementing measurement software and filters
- Typical industries: automotive, aerospace, medical devices, precision engineering and any sector requiring controlled surface function and interchangeability.
Related standards
By aligning drawing indications with the rules in EN ISO 21920-3:2022, organizations ensure consistent surface texture measurement, reporting and acceptance across the supply chain.
