ISO 14405-2:2018

Overview

ISO 14405-2:2018 - Geometrical product specifications (GPS) - Dimensional tolerancing - Part 2: Dimensions other than linear or angular sizes - addresses how to specify and interpret dimensions that are not linear sizes or angular sizes on engineering drawings, CAD models and other product documentation. The standard explains the ambiguity caused by using ± tolerancing for such dimensions and shows how geometrical specifications (per ISO 1101) provide unambiguous control. It is part of the ISO 14405 series and the wider GPS matrix for dimensional and geometrical product specifications.

Key topics and technical requirements

• Specification ambiguity: Explains why ± tolerancing for distances or features that are not features of size can be ambiguous on real workpieces because of form and orientation deviations.
• Recommendation to use geometrical specifications: For non-size dimensions, geometrical tolerancing (position, orientation, form) is recommended to remove ambiguity.
• Illustrative examples: Clause 7 provides multiple examples (linear distances between integral or derived features, radii, arc lengths, step heights, angular distances) showing ambiguous ± tolerance cases and unambiguous geometrical alternatives.
• Normative references and decision rules: Relies on ISO 1101 (geometrical tolerancing), ISO 14405-1 and -3 (linear and angular sizes), ISO 8015 (fundamentals), and ISO 129-1 (presentation rules). Default decision rules from ISO 14253-1 and GPS matrix relations (Annex B) apply.
• Units and defaults: Linear units default to millimetres (mm); angular units to degrees. Rules for indicating units are given.
• Annexes: Annex A explains ambiguity examples; Annex B relates this part to the GPS matrix model.

Practical applications and users

Who uses ISO 14405-2:

• Design and mechanical engineers specifying tolerances on drawings or 3D models
• CAD modelers applying tolerancing annotations in digital product definitions (PMI)
• Metrologists and quality engineers creating inspection plans and defining measurement methods
• Manufacturing engineers and suppliers interpreting tolerances for process capability
• Standards committees and technical authors aligning documentation with GPS principles

Practical benefits:

• Eliminates interpretation disputes between design, production and inspection by replacing ambiguous ± dimensioning with clear geometrical controls
• Improves inspection reproducibility and traceability of acceptance criteria
• Facilitates Model-Based Definition (MBD) and digital workflows that depend on unambiguous specification semantics

Related standards

• ISO 1101 - Geometrical tolerancing (rules for geometrical specifications)
• ISO 14405-1 - Linear sizes
• ISO 14405-3 - Angular sizes
• ISO 8015, ISO 129-1, ISO 17450 series - GPS fundamentals and presentation

Keywords: ISO 14405-2:2018, geometrical product specifications, dimensional tolerancing, ± tolerancing ambiguity, geometrical tolerancing, GPS, ISO 1101, drawing tolerances, metrology, engineering design.