: The letter "B" represents the tolerance class for general linear and angular dimensions. EN ISO 13920 categorizes acceptable deviations into four tolerance classes based on customary workshop accuracy:
This notation tells the welder: "Use Class B for most features, but tighten up this specific surface."
: The international standard for "General tolerances for welded constructions". : Refers to the tolerance class for linear and angular dimensions
This is the tolerance class for linear dimensions. For a length of 2 meters, a "B" rating allows for roughly of deviation. The "F" (Form): en iso 13920-bf
The second letter defines tolerances for straightness, flatness, and parallelism.
For the "F" class in shape and position tolerances (covering straightness, flatness, and parallelism), the permissible deviation (in millimeters) depends on the nominal dimension of the inspected feature:
Interpretation: If you weld a frame with a nominal length of 1,500 mm, the actual finished length can be between 1,495 mm and 1,505 mm and still be compliant with EN ISO 13920-BF. : The letter "B" represents the tolerance class
Ensures that large welded frames don't warp or twist beyond a functional limit during the cooling process. 🏗️ Why It Matters (The "Interesting" Part)
Mastering EN ISO 13920-BF: The Blueprint for Welded Construction Tolerances
| | EN ISO 13920 Tolerance Class B: Limit Deviation (± mm) | | :--- | :--- | | 2 to 30 | ± 2 | | >30 to 120 | ± 2 | | >120 to 400 | ± 3 | | >400 to 1000 | ± 4 | | >1000 to 2000 | ± 6 | | >2000 to 4000 | ± 8 | | >4000 to 8000 | ± 10 | | >8000 to 12000 | ± 12 | | >12000 to 16000 | ± 14 | | >16000 to 20000 | ± 16 | | >20000 | As agreed upon between parties. | For a length of 2 meters, a "B"
"EN ISO 13920-B, BUT FLATNESS OF MOUNTING FACE F1 (reference surface) TO BE HELD TO CLASS A (±0.5 mm)"
ISO 13920:2023 - Welding Tolerances for Dimensions and Positions
The drawing note "ISO 2768-mK / EN ISO 13920-BF / ISO 9013-331" is a common sight on technical drawings, demonstrating how these standards work together to govern different aspects of a single manufactured part.
Q: How do I determine the tolerance class for my welded construction? A: The tolerance class depends on the specific application, industry, and required level of precision. Refer to the standard or consult with a qualified engineer or inspector.
: This refers to the tolerance class for shape and position (straightness, flatness, and parallelism) . Key Features of ISO 13920 ISO 13920 An Explained Guide to Welding General Tolerances