Overview
SIST EN ISO 128-2:2023 / ISO 128-2:2022 specifies the basic conventions for lines used in technical product documentation (TPD). It defines the types of lines used in technical drawings (diagrams, plans, maps), their designations, configurations and general draughting rules. The standard also covers presentation rules for leader lines and reference lines, arrangement of instructions, and includes industry-specific annexes for mechanical, construction and shipbuilding drawings. This edition replaces the 2020 version and aligns with ISO 128 series principles for consistent representation in engineering and architectural documentation.
Key topics and technical requirements
- Types of lines and subtypes: Identification and naming of basic line types (continuous and non-continuous) and permitted variations and combinations.
- Line dimensions and width: Guidance on line width selection, acceptable deviations and how width affects graphical clarity.
- Line configuration and spacing: Rules for spacing of graphical basic elements that compose non-continuous lines (e.g., dashes, dots) and for arranging parallel lines.
- Draughting of lines: Best practices for drawing lines, including junctions, terminations and positioning of overlapping lines (hierarchy rules).
- Leader and reference lines: Conventions for presentation, components and placement of instructions or notes on or adjacent to leader lines.
- Colours and designation: General notes on using colour and marking lines for clear, unambiguous documentation.
- CAD implementation: Annex A provides guidance for preparing lines in CAD systems to ensure digital drawings comply with the standard.
- Industry-specific annexes: Normative and informative annexes (B–G) giving examples and applications for construction, mechanical engineering and shipbuilding technical drawings.
Practical applications
- Create consistent, standardized engineering drawings, shop drawings, construction plans and shipbuilding documentation.
- Define CAD layer and style standards (line types, line weights and leader conventions) to ensure interoperability across teams and systems.
- Improve communication between design, manufacturing and regulatory stakeholders by using uniform line conventions to avoid misinterpretation.
- Train drafters, CAD operators and quality reviewers on standardized representation for product documentation and compliance checks.
Who should use this standard
- Mechanical, civil and naval engineers; architects and draughting professionals
- CAD administrators and BIM managers establishing templates and line libraries
- Technical illustrators, document control and quality assurance teams
- Standards bodies and organizations producing or checking TPD for procurement, manufacturing or regulatory submission
Related standards
- Part of the ISO 128 series on general principles of representation. Use ISO 128-2 together with other ISO 128 parts for complete guidance on projection, views and complementary drawing conventions.
Keywords: ISO 128-2, SIST EN ISO 128-2:2023, technical product documentation, basic conventions for lines, technical drawings, leader lines, reference lines, CAD drawing standards.