En Iso 13920-bf 💯 Fresh

For parts where centering is important (e.g., a boss on a plate).

| Nominal Size (mm) | Permitted Deviation (Class B) | | :--- | :--- | | Up to 120 | 1 mm | | 120 to 400 | 2 mm | | Over 400 | 3 mm |

The first letter defines tolerances for lengths, widths, and angles.

This guide explains the technical specifications for EN ISO 13920-BF, an international standard used to define general tolerances for welded constructions. Overview of EN ISO 13920

The ISO 13920 standard specifies general tolerances for linear and angular dimensions, as well as for shape and position of welded structures. It is designed to ensure functional suitability in manufacturing without requiring excessive precision that could increase costs unnecessarily. Breaking Down "BF" en iso 13920-bf

When a drawing specifies EN ISO 13920-BF, it is identifying two specific tolerance classes:

B (Tolerance Class for Linear and Angular Dimensions): This is the "Medium" class for lengths and angles. It defines the allowable deviation for measurements like the length of a beam or the degree of an angle.

F (Tolerance Class for Shape and Position): This specifies the allowable variations for geometric attributes such as straightness, flatness, and parallelism. Key Tolerance Areas

The standard covers four main categories of dimensional variations: Linear Dimensions: Lengths of welded parts. Angular Dimensions: Angles between welded components.

Straightness and Flatness: How "true" a surface or edge must be. Shape and position tolerances

Parallelism and Alignment: Ensuring parts are correctly positioned relative to each other. Application and Usage

Drawings: Engineers indicate this standard in the "General Tolerances" block of a technical drawing (e.g., "General Tolerance: EN ISO 13920-BF") to avoid labeling every single dimension with a specific tolerance.

Industry Use: It is commonly used in heavy-duty fabrication, such as for filtration distributors, corona rings, and offshore mattressing structures.

Revision Note: The original 1996 version (EN ISO 13920:1996) was revised by the updated ISO 13920:2023 standard. ISO 13920 An Explained Guide to Welding General Tolerances

To truly understand "EN ISO 13920-BF," you must know the numbers. Below are the key tolerance ranges for Class B (Medium). Tolerance grades and classes

This standard specifies tolerance classes (fine, medium, coarse) for:

It does not define welding symbol positions (covered by ISO 2553), but ISO 13920-BF is an internal drawing notation referencing backing weld requirements in conjunction with tolerances.