ISO 129-1:2018

Overview

ISO 129-1:2018 - Technical product documentation (TPD) - Presentation of dimensions and tolerances - Part 1: General principles establishes the general rules for how dimensions and associated tolerance indications are presented on technical drawings. The standard applies primarily to 2D technical drawings across all disciplines and trades and can also be used for 3D applications. ISO 129-1:2018 specifies presentation conventions (layout, symbols and notation) but does not define the meaning or application of dimensional tolerances - see ISO 14405‑1 for tolerancing principles.

Key topics and requirements

ISO 129-1:2018 covers the core elements needed for consistent, unambiguous dimensioning and includes:

• Presentation rules for dimensions, repeated and auxiliary dimensions, and theoretically exact dimensions
• Elements of dimensioning: property indicators, dimension lines, extension lines, terminators, leader lines and dimensional values
• Symbols and notation: surface indicators, developed length, “between” indicator, diameters, radii, spheres, arcs and special graphical symbols
• Arrangement methods: chain, parallel, running (uni-/bidirectional), coordinate (Cartesian and polar) and combined dimensioning
• Tabular dimensioning, complement indications, flag notes and textual instructions for special cases
• Presentation of dimensional tolerances (format and placement) but not the interpretation of tolerance intent or functional tolerancing rules
• Guidance for drawing consistency, characters and annotation placement; notes on nominal (model) vs non‑ideal (skin) representations

Practical applications

ISO 129-1:2018 is designed to improve clarity and interoperability in engineering documentation. Typical uses:

• Producing standardized CAD drawings and 2D prints for mechanical design, manufacturing and inspection
• Creating drawing templates and company drawing standards to ensure consistent dimension presentation
• Training drafters, CAD operators and technical illustrators in accepted dimensioning conventions
• Supporting quality control and metrology by reducing ambiguity in dimension placement and notation

Who benefits: mechanical engineers, CAD designers, technical product documentation specialists, manufacturing engineers, quality/inspection personnel and CAM programmers.

Related standards

• ISO 14405‑1 - Geometrical tolerancing principles (tolerancing meaning and application)
• ISO 29845 - Applicability of rules to different drawing types
• ISO 6284 - Additional guidance for construction engineering
• Referenced GPS (Geometrical Product Specification) standards for advanced tolerancing topics

For authoritative text and purchase, consult the ISO website (www.iso.org).