En Iso 13920-bf

The designation EN ISO 13920-BF refers to a specific set of general tolerances for welded constructions, combining two distinct classes of accuracy defined by the ISO 13920 standard. Breakdown of the Code

The code BF specifies the precision level required for the manufacturing of a welded part:

B: Represents the tolerance class for linear and angular dimensions. Class B is considered "medium" or "customary workshop accuracy".

F: Represents the tolerance class for shape and position (such as straightness, flatness, and parallelism). Tolerance Tables for EN ISO 13920-BF en iso 13920-bf

These tolerances apply when no specific tolerance is indicated for a dimension on a technical drawing. 1. Linear Dimensions (Class B)

Tolerances for lengths, such as external sizes, internal sizes, and step sizes. Range of nominal sizes (mm) Tolerance (mm) ±1plus or minus 1 ±2plus or minus 2 120 to 400 ±2plus or minus 2 400 to 1000 ±3plus or minus 3 1000 to 2000 ±4plus or minus 4 2000 to 4000 ±6plus or minus 6 2. Shape and Position (Class F) Tolerances for straightness, flatness, and parallelism. Range of nominal sizes (mm) Tolerance (mm) Up to 1000 1000 to 2000 2000 to 4000 4000 to 8000 Application in Industry This standard is commonly cited in technical drawings for:

Steel Construction: Used by firms like Hazemag and C.C. JENSEN to ensure structural components fit together without excessive machining costs. The designation EN ISO 13920-BF refers to a

Mechanical Engineering: Often paired with ISO 2768-mK (which covers tolerances for machined parts) to provide a complete specification for assemblies that include both welded and machined features.

Quality Control: Serves as the basis for inspection reports to determine if a welded assembly meets the functional requirements of the design. Specification Steel Construction - hazemag

Development Review: EN ISO 13920-BF

Standard: EN ISO 13920 (Welding – General tolerances for welded constructions) Class: BF Status: Active (Harmonized across EU) Development Review: EN ISO 13920-BF Standard: EN ISO

When Should You Use ISO 13920 Class B?

If your project calls for Class B tolerances (whether BD or BC), you are working within the most common parameters for general fabrication.

Ideal applications include:

Class B allows for the natural thermal distortion that occurs during welding without requiring expensive post-weld machining or straightening processes.

1. Executive Summary

EN ISO 13920-BF defines a specific set of "General Tolerances" for welded structures. It is intended to replace specific tolerance indications on technical drawings where high precision is not critical. The "BF" classification represents a Medium/Fine tolerance grade, making it the most commonly specified default for structural steel and general machinery welding where aesthetics and fit-up are important, but machining-level precision is not required.