By defining a "medium" standard, it balances the high cost of extreme precision with the need for stability. Application in Industry
Therefore, a callout of indicates that a workshop must meet medium precision constraints across all dimensional, angular, and geometric orientations. Linear Dimension Tolerances (Class B)
Class B specifies the following typical tolerances based on the length ( ) of the part: plus or minus 1.0 plus or minus 1.0 plus or minus 3.0 plus or minus 6.0 (Tolerances continue to scale for larger structures) Shape and Position (Class F)
: ±15 minutes of a degree (approx. ±4.5 mm per meter). en iso 13920-bf
Understanding EN ISO 13920-BF: The Benchmark for Welded Steel Structures
This is the tolerance class for lengths (like the distance between two plates) and angles. Class
This refers to the tolerance for straightness, flatness, and parallelism. While linear dimensions use letters A through D, shape and position tolerances use E through H. Class F is the second-most precise level in this category (often considered "Medium" for shape). Why Use EN ISO 13920-BF? By defining a "medium" standard, it balances the
: This letter assigns Tolerance Class F to all geometrical aspects, controlling the acceptable limits for straightness, flatness, and parallelism.
These values apply strictly to lengths, widths, heights, and thicknesses of welded fabrications. Per the ISO 13920 Guidelines , the allowed limits for Class B include: Nominal Size Range ( Class B Tolerance limit ( ±plus or minus ±plus or minus Over 30 up to 120 ±plus or minus Over 120 up to 400 ±plus or minus Over 400 up to 1,000 ±plus or minus Over 1,000 up to 2,000 ±plus or minus Over 2,000 up to 4,000 ±plus or minus Over 4,000 up to 8,000 ±plus or minus Over 8,000 up to 12,000 ±plus or minus 2. Angular Dimensions
: Represents the tolerance class for shape and position (such as straightness, flatness, and parallelism). Tolerance Tables for EN ISO 13920-BF While linear dimensions use letters A through D,
Individual pieces prior to final assembly. Welded Structures: Structures containing welded joints.
If you have a welded beam with a nominal length of :