ISO 128-2:2022

Overview

ISO 128-2:2022 - part of the Technical Product Documentation (TPD) series - defines the basic conventions for lines used in technical drawings (diagrams, plans, maps and related product documentation). The standard establishes line types, designations, configurations and general draughting rules, plus rules for leader and reference lines and the arrangement of instructions on or at leader lines. Annexes cover field‑specific guidance for mechanical, construction and shipbuilding drawings and include CAD preparation notes.

Key topics and technical requirements

• Types of lines and subtypes: identification of basic line families and subtype distinctions (by width and application).
• Graphical basic elements: definition of elements (dots, dashes, continuous segments) that form lines and non‑continuous line calculation guidance (Annex A).
• Line dimensions and width: provisions on line width, permissible deviations and configuration principles.
• Draughting rules: spacing, junction handling, placement of overlapping lines and hierarchy when lines intersect.
• Leader and reference lines: presentation rules, components, reference line representation and arrangement of associated instructions or labels.
• Colours and designation: guidance on colour use (where applicable) and how line types should be designated on drawings.
• Field‑specific annexes: normative and informative annexes for construction (B, C), mechanical engineering (D, E) and shipbuilding (F, G) applications.
• CAD considerations: Annex A provides practical info for preparing lines with CAD systems and ensuring conformity with the standard.

Practical applications - who uses it and why

• Mechanical and civil drafters, shipbuilders and CAD engineers: apply consistent line conventions across parts, assemblies and construction drawings.
• Technical authors and documentation specialists: ensure product documentation meets ISO TPD conventions for clarity and legal/contractual acceptance.
• Manufacturing, QA and procurement teams: reduce interpretation errors by standardizing line presentation and hierarchies on drawings.
• Standards managers and engineering educators: integrate ISO 128-2 into company drawing practices, templates and training.

Benefits include improved interoperability of drawings, reduced misinterpretation in manufacturing/installation, and easier automation of CAD-to-document workflows.

Related standards

ISO 128-2 is part of the ISO 128 series (general principles of representation). Relevant cross‑references in the document include: ISO 128-3, ISO 129-1, ISO 1101, and other TPD and drawing standards cited in the normative references for dimensioning, tolerancing and domain‑specific drawing practices. Use ISO 128-2 together with these standards to create complete, standards‑compliant technical documentation.