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These values apply to nominal sizes such as lengths, widths, heights, and distances between components. Nominal Size Range (mm) Tolerance Class b (mm) Over 30 to 120 Over 120 to 400 Over 400 to 1000 Over 1000 to 2000 Over 2000 to 4000 Over 4000 to 8000 Over 8000 to 12000 Over 12000 to 16000 Over 16000 to 20000 Over 20000 Tolerances for Angular Dimensions (Class b)
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):
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 en iso 13920-bf
The EN ISO 13920 code utilizes a dual-letter classification system to dictate manufacturing limits. In the case of , the letters break down as follows:
In the ISO 13920 coding system, the second letter regarding geometrical tolerances is either C (Fine) or D (Medium). There is no "F" class for geometry. These values apply to nominal sizes such as
If the final measurement shows length = 2,008 mm (violation by 3 mm), the part fails. The solution? Re-cut side members 5 mm short next time to compensate for weld shrinkage.
To truly understand "EN ISO 13920-BF," you must know the numbers. Below are the key tolerance ranges for (Medium). comparison table The EN ISO 13920 code utilizes
(lengths and angles). Class B is generally considered "medium" or standard workshop accuracy. : Refers to the tolerance class for shape and position
Understanding EN ISO 13920-BF: Tolerances for Welded Structures
The standard was recently refreshed as ISO 13920:2023 , replacing the long-standing 1996 version to align with modern ISO styles and references . 📋 Key Technical Categories
Choosing "BF" instead of a tighter class (like "A") can save thousands in labor. It acknowledges that heat from welding naturally distorts metal, so "perfect" isn't always practical or necessary.
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