Overview
EN ISO 1660:2017 - "Geometrical product specifications (GPS) - Geometrical tolerancing - Profile tolerancing (ISO 1660:2017)" is a CEN-adopted ISO standard that defines the rules for profile tolerancing of both integral and derived features. It sets out how to apply line profile and surface profile characteristic symbols (as in ISO 1101) and establishes decision rules and tools for specifying profile tolerance zones on 2D drawings and 3D CAD models.
Key topics
- Scope and purpose: Rules for specifying profile tolerances for non‑straight lines, non‑flat surfaces and simpler features (planes, cylinders, etc.).
- Theoretically exact feature (TEF): Clarified rules for defining the nominal geometry used as a reference for tolerance application.
- Toleranced feature definition: Updated to follow the feature principle and GPS conventions (see ISO 8015).
- Tolerance zone rules: Default and additional rules (listed A–L) cover:
- Rule A–C: definition of TEF, type of toleranced feature, and tolerance zone definition.
- Rule D–L: additional specification elements - restricted and compound features, unequally disposed zones, linear/angular offsets, variable tolerance width, filtering, associations and non‑rigid parts.
- Annexes: Informative guidance on compound features, illustrative examples, historical practices and relation to the GPS matrix model.
- Meta-rules: References and alignment with GPS principles (ISO 14638), decision rules (ISO 14253‑1), and CAD attachment practices (ISO 16792).
Applications
EN ISO 1660:2017 is used wherever precise profile control is required:
- Design engineers specifying complex surface and line tolerances on drawings and 3D models.
- CAD modelers and PLM teams attaching unambiguous profile tolerancing to digital definitions.
- Manufacturing engineers and shop floor personnel interpreting profile tolerances for process selection.
- Quality and metrology teams creating inspection plans, CMM programs and acceptance criteria for surface/profile verification.
- Suppliers and contract manufacturers receiving specification-compliant profile requirements.
Practical benefits include clearer nominal/real feature definition, rules for non‑uniform tolerance zones and improved interoperability between design, manufacturing and inspection through consistent GPS profile tolerancing.
Related standards
Keywords: EN ISO 1660:2017, profile tolerancing, geometrical product specifications, GPS, ISO 1101, tolerance zone, theoretically exact feature, GD&T, CAD, metrology.