Overview
ISO 129-5:2018 - Technical product documentation - Indication of dimensions and tolerances - Part 5: Dimensioning of structural metal work specifies how to dimension drawings for structural metal work made mainly of plates, bars and profile sections. The standard defines clear rules for representing profile codes, simplified dimensioning, datum lines and specific features (bolts, rivets, welds) to ensure consistent, unambiguous technical product documentation for fabrication and inspection.
Key topics and requirements
- Datum and basic rules
- Dimensioning shall follow general principles of ISO 129-1.
- The centroidal line of a component is the preferred datum line for dimensioning.
- Dimensions must be simple, clear and readable; dimension lines may be omitted for clarity where appropriate.
- Simplified dimensioning
- Use schematic representation methods conforming to ISO 5261 for bars and profile sections.
- Arc lengths and bent radii must be dimensioned correctly (e.g., radius on bent parts).
- Profile coding and graphical symbols
- Profile sections use a standardized profile code (graphical symbol/letter code + standard number + main sizes + cutting length), with conventions for cold-formed sections (type code “C”).
- Annex A provides the profile graphical symbols and their proportions.
- Profile codes should be shown close to the corresponding component or in tabular form for multiple parts.
- Detailing requirements
- Dimension features along main axes; indicate centroidal lines and separate intersecting centroidal lines before dimensioning.
- Specific instructions for unequal leg angles, gusset plates, batten plates and connection detailing (bolt hole centers, distances).
- Bolts, rivets and welding
- Bolts and rivets may be shown simplified and identified with leader lines and symbols (see Table 4).
- Annex B outlines welding dimensioning using welding symbol system A (ISO 2253) for typical welded components.
Applications and users
ISO 129-5:2018 is used by:
- Structural steel detailers and fabricators for producing shop drawings
- Mechanical and structural engineers creating erection and assembly documentation
- CAD draughtsmen standardizing profile codes and part lists
- Quality inspectors and procurement teams verifying dimensions and tolerances
- Technical documentation specialists ensuring compliant drawings for manufacturing and construction
Practical applications include shop fabrication drawings, cutting lists, connection details, bolt/rivet specifications and welded-joint dimensioning for structural metalwork projects.
Related standards
- ISO 129-1 (general principles)
- ISO 5261 (simplified representation of bars and profiles)
- ISO 10209 (vocabulary for technical drawings)
- ISO 657 series (hot-rolled steel section dimensions)
- ISO 129-4 (shipbuilding dimensioning)
- ISO 2253 (welding symbol system A)
Keywords: ISO 129-5:2018, technical product documentation, dimensioning, structural metal work, profile code, centroidal line, bolts and rivets, welding dimensioning.
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