ISO 13920:2023

Overview

ISO 13920:2023 - Welding - General tolerances for welded constructions - Dimensions for lengths and angles, shape and position - defines uniform, workshop-based tolerances for welded constructions. It specifies general tolerances for linear and angular dimensions and for shape and position (straightness, flatness, parallelism) in four tolerance classes. The standard is intended to be used on drawings as a convenient shorthand (e.g., ISO 13920-B or ISO 13920-BE) when individual tolerances are not specified.

Key topics and requirements

• Tolerance classes: Four primary classes (A, B, C, D) for linear and angular tolerances, selectable based on functional requirements and customary workshop accuracy.
• Form tolerances: Separate classes (e.g., E–H) for straightness, flatness and parallelism of surfaces and overall weldment dimensions.
• Independency principle: Applies ISO 8015 - dimensional and geometrical tolerances are independent of one another.
• Application scope: Applies to weldments, welding assemblies and welded structures; special provisions may be required for complex or large structures.
• Drawing indications: The selected tolerance class must be shown on the manufacturing drawing; drawings without an adequate reference to general tolerances are deemed incomplete (except temporary dimensions).
• Testing and measuring: Recommends commonly used measuring devices - straightedges, tape measures, vernier callipers (ISO 13385), dial gauges (ISO 463), optical devices, water levels and surface plates - and gives test methods for straightness, flatness and parallelism.
• Non-conformities: Acceptance of parts not meeting ISO 13920 is determined by suitability for intended purpose; deviations may be accepted by agreement.

Practical applications and users

ISO 13920:2023 is practical for:

• Welders and fabricators seeking clear production tolerances for shop work
• Design and detailing engineers specifying tolerances on fabrication drawings
• Quality, inspection and QA/QC personnel performing acceptance checks
• Procurement and project managers ensuring contract clarity for welded components Common applications include structural steelwork, industrial equipment, frames, tanks and general welded assemblies where functional fit and workshop-level accuracy are required.

Related standards

• ISO 8015 - Geometrical product specifications: fundamental independency principle.
• ISO 1101 - Geometrical tolerancing for form and position (referenced for additional geometric symbols).
• ISO 13385-1 / ISO 13385-2 and ISO 463 - Recommended metrological equipment standards for calipers and dial gauges.

Keywords: ISO 13920:2023, welding tolerances, welded constructions, tolerance classes, linear and angular dimensions, shape and position, straightness, flatness, parallelism, ISO 8015.