En Iso 13920-bf Today

Here is the breakdown:

Summary answer to your query:

"EN ISO 13920-BF" is not a valid designation in the standard itself (ISO 13920 has no BF). It most likely means:
"Weld edge preparation type BF according to ISO 9692-1, with general tolerances according to EN ISO 13920."

If you need the exact dimensional tolerances for such a preparation (e.g., root face, gap), that would be found in ISO 9692-1, not ISO 13920.

The designation EN ISO 13920-BF a specific set of general tolerances for welded constructions, combining two different accuracy classes defined in the for linear/angular dimensions and for form and position Breakdwon of "BF" When this standard is cited on a drawing (e.g., ISO 13920-BF ), it indicates the following requirements: B (Linear/Angular Dimensions):

This is the "Medium" (mean) tolerance class for lengths and angles. F (Shape and Position):

This class governs tolerances for straightness, flatness, and parallelism. Key Tolerance Categories ISO 13920 standard

replaces individual tolerance callouts on drawings with general workshop-based standards. CertBetter Tolerance Classes Available Class in "BF" Description Linear & Angular A, B, C, D Medium Accuracy

: Standard workshop accuracy for most general steel constructions. Shape & Position E, F, G, H Medium Form Tolerance

: Defines limits for straightness and flatness based on the largest dimension of the part. Application Rules ISO 13920 An Explained Guide to Welding General Tolerances

EN ISO 13920-BF is a combined tolerance designation used in the fabrication of welded structures to specify acceptable deviations in dimensions and shape without detailing every single measurement on a technical drawing. Standard Breakdown EN ISO 13920

: The international standard for "General tolerances for welded constructions". : Refers to the tolerance class for linear and angular dimensions

(lengths and angles). Class B is generally considered "medium" or standard workshop accuracy. : Refers to the tolerance class for shape and position en iso 13920-bf

(straightness, flatness, and parallelism). Class F is often used for structural assemblies where moderate precision is required. Summary of Tolerances

The exact deviation allowed depends on the nominal size of the component. Larger components are permitted greater absolute deviations than smaller ones. Linear Dimensions (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)

Class F governs how much a part can warp or sit out of alignment (straightness, flatness, and parallelism): : Max deviation of : Max deviation of : Max deviation of Why This is Used Using a general tolerance like EN ISO 13920-BF

simplifies technical drawings by removing the need for hundreds of individual plus or minus

callouts. It ensures that different fabrication shops produce parts to a consistent quality level, reducing the risk of components not fitting together during final assembly. comparison table

of the different tolerance classes (A, B, C, and D) to see which fits your project best? EN ISO 13920

The designation EN ISO 13920-BF refers to a specific combination of tolerance classes for welded constructions. It is a standard shorthand used in engineering drawings to define acceptable variations in dimensions without needing to label every single part. Breaking Down "BF"

The code is split into two distinct parts that cover different geometric features: B (Linear and Angular Dimensions):

This is the tolerance class for lengths (like the distance between two plates) and angles. Class

is considered "medium" or customary workshop accuracy for welded parts. F (Shape and Position): This refers specifically to straightness, flatness, and parallelism Here is the breakdown:

defines how much a welded beam can bow or a plate can warp during the welding process. American National Standards Institute - ANSI Key Features of the Standard

ISO 13920:2023 - Welding Tolerances for Dimensions and Positions

Understanding EN ISO 13920-BF: A Guide to Welding Tolerances

The designation EN ISO 13920-BF refers to a specific set of general tolerances for welded constructions. It combines two distinct tolerance classes defined by the international standard ISO 13920: Class B for linear and angular dimensions, and Class F for straightness, flatness, and parallelism.

This standard is essential for ensuring consistency and quality in structural steel fabrication when individual tolerances are not specified on a drawing. 1. Breakdown of the "BF" Designation

The "BF" suffix is a shorthand used in engineering drawings to indicate the level of accuracy required for a welded assembly.

Class B (Medium): This is the most common tolerance class used in general engineering and construction. It covers linear dimensions (lengths, widths, heights) and angular dimensions.

Class F: This class specifically governs the geometric tolerances of the weldment, including how straight a part is or how flat a surface must be. 2. Tolerance Tables for Class B (Linear & Angular)

According to technical guides from Scribd and Modulus Metal, the permitted deviations for Class B depend on the size of the component: Range of Nominal Size (mm) Linear Tolerance (± mm) Over 30 to 120 Over 120 to 400 Over 400 to 1,000 Over 1,000 to 2,000

For Angular Dimensions in Class B, the tolerance is determined by the length of the shorter leg of the angle: Up to 400 mm: ± 45 minutes of a degree. Over 400 to 1,000 mm: ± 30 minutes. Over 1,000 mm: ± 20 minutes. 3. Geometric Tolerances for Class F

Class F defines the allowable variation for the shape and position of the structure. Common tolerances for Class F include: Over 30 to 120 mm: +1 mm. Over 120 to 400 mm: +1.5 mm. Over 400 to 1,000 mm: +3 mm. 4. Why Use EN ISO 13920-BF? EN ISO 13920 is the standard for Welding

Adopting these general tolerances simplifies the design and manufacturing process by:

ISO 13920 Welding General tolerances for welded constructions

This review is designed for engineering, quality assurance, and drafting departments to determine if this standard is suitable for a given project.

Mistake #4: Confusing Symmetry with Coaxiality

Symmetry tolerance (Class B = up to 3 mm) is not the same as coaxiality of bores. For two bores that must align for a shaft, use a separate geometric tolerance (GD&T), not ISO 13920.

1. Overview of EN ISO 13920

EN ISO 13920 is the European adoption of the international standard ISO 13920:1996 – Welding – General tolerances for welded constructions.
It specifies general tolerances for linear and angular dimensions, flatness, straightness, and parallelism for welded structures, where no individual tolerances are indicated on the drawing.

The standard applies to:

2. Understanding the "BF" Designation

In the context of EN ISO 13920, "BF" is not a tolerance class from the standard itself. Instead, it appears in welding symbols or technical notes to denote a specific weld preparation shape – typically Backing run with Flat face or Backing + Flat.

However, in practice, when designers write "EN ISO 13920-BF", they usually mean:

"General tolerances according to EN ISO 13920 apply, and the weld preparation follows a 'BF' type (often from ISO 9692-1 – butt weld preparation)."

2. Scope of EN ISO 13920

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.