Iso 13920-d Jun 2026

Compliance can often be verified with standard tools like tape measures and straightedges rather than precision gauges.

The standard excludes complex dimensions that rely on machining after welding. Instead, it focuses on the inherent variability of thermal joining processes.

For nominal sizes ranging from 30 mm up to 1200 mm, Class D permits deviations of approximately ±1.5 mm to ±3 mm. For example, a cut plate intended to be 500 mm long under ISO 13920-D can be accepted between 498.5 mm and 501.5 mm. This is significantly looser than Class B (which would be ~±0.8 mm for the same length) but tighter than Class E (~±5 mm). This tolerance allows for thermal cutting (oxy-fuel or plasma) without secondary machining. iso 13920-d

is not a "low-quality" standard. It is a strategic tool for cost-effective heavy fabrication. By accepting coarser tolerances, you align engineering expectations with physical reality of welding processes.

Tolerances for linear dimensions are based on the nominal length, while angular tolerances are based on the length of the shorter leg of the angle. ISO - International Organization for Standardization Why Use Class D? Compliance can often be verified with standard tools

, the international standard for general tolerances of welded constructions. This standard is used to simplify engineering drawings by providing a default set of acceptable deviations for linear and angular dimensions, as well as shape and position, specifically for welded parts. ISO - International Organization for Standardization Key Characteristics of ISO 13920-D

For angles (e.g., 45° miters), the tolerance is not a fixed degree but a length-based deviation over the leg length. For nominal sizes ranging from 30 mm up

ISO 13920 specifies four classes—, B (Medium) , C (Coarse) , and D (Very Coarse) —for linear and angular dimensions. While Class B is the most common for general engineering, Class D allows for the largest deviations. Nominal Size Range ( Class D Tolerance ( Comparison: Class B ( Over 120 to 400 Over 1,000 to 2,000 Over 4,000 to 8,000 Over 16,000 to 20,000 Values based on standardized tolerance tables . Scope and Dimensions Covered

The standard applies to . It focuses on four primary geometric aspects: Linear Dimensions: Length, width, and height.

Geometric tolerancing is a method of specifying the acceptable limits of variation in the shape, size, and orientation of features on an engineering drawing. It provides a way to communicate the design intent and ensure that manufactured parts meet the required specifications. Geometric tolerancing is essential for ensuring the proper functioning, assembly, and interchangeability of parts.