Overview
SIST EN ISO 1101:2017 (ISO 1101:2017) is the international standard that defines the symbol language and interpretation rules for geometrical product specifications (GPS). It establishes the foundation for indicating and reading geometrical tolerances on engineering drawings and CAD models, covering tolerances of form, orientation, location and run‑out. The standard supports explicit visible annotation (including Theoretically Exact Dimensions - TEDs) and notes that equivalent indications may be attached indirectly to 3D CAD models (see ISO 16792).
Key topics and requirements
- Symbol language and rules: Standardized symbols and syntax for expressing geometrical tolerancing unambiguously.
- Toleranced features and tolerance zones: Definitions and defaults for tolerance zones, including variable‑width, cylindrical and spherical zones.
- Datums and datum systems: Rules for datum indications and how datum references control orientation and location.
- Geometrical specifications: Formal definitions for straightness, flatness, roundness, cylindricity, line/surface profile, parallelism, and other characteristics.
- Annotation conventions: How to present tolerance indicators, feature identifiers, stacked tolerances, supplementary indications and drawing defaults.
- Advanced constructs: Intersection planes, orientation planes, direction features, collection planes, projected toleranced features and restrictive specifications.
- CAD integration: Guidance that specifications may be indicated indirectly via 3D CAD (ISO 16792) with possible query/metadata access instead of visible annotation.
(These topics reflect the standard’s content structure and mandatory interpretation rules; specific measurement procedures and supplemental details are provided by referenced standards.)
Practical applications
- Create unambiguous, standardized mechanical drawings and technical documentation for manufacturing.
- Communicate tolerancing requirements between design, manufacturing and quality teams.
- Define inspection criteria for metrology, coordinate measuring machines (CMM) and surface analysis.
- Annotate 3D CAD models with GPS data for model‑based definition (MBD) workflows.
- Support contractual specifications between OEMs and suppliers to ensure consistent part acceptance.
Who should use this standard
- Mechanical, manufacturing and design engineers
- CAD modelers and MBD practitioners
- Quality engineers, metrologists and inspection labs
- Technical drafters and standards managers
- Contract engineers and sourcing/specification teams
Related standards
- ISO 16792 (CAD product definition for indirect indication on 3D models) - explicitly referenced.
- Other ISO/CEN GPS standards (referenced in Clause 2 and Tables 3–4) provide complementary measurement, verification and application details.
Keywords: ISO 1101, ISO 1101:2017, GPS, geometrical tolerancing, tolerances of form orientation location run‑out, TED, 3D CAD, datum, tolerance zone, geometrical product specifications.