En Iso 13920-bf 【PRO】

These tolerances apply to external and internal lengths, step heights, and center distances.

| Nominal Size Range (mm) | Permitted Deviation (Class B) | | :--- | :--- | | 30 to 120 | ± 2 mm | | 120 to 400 | ± 3 mm | | 400 to 1,000 | ± 4 mm | | 1,000 to 2,000 | ± 5 mm | | 2,000 to 4,000 | ± 6 mm | | 4,000 to 8,000 | ± 7 mm | | > 8,000 | ± 8 mm + 0.5 mm per 1,000 mm |

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.

If you are a design engineer, using this standard correctly will save your workshop hours of confusion. en iso 13920-bf

Incorrect usage:

"USE STANDARD WELDING TOLERANCES"

Correct usage (per ISO guidelines):

"GENERAL TOLERANCES: EN ISO 13920 – B (MEDIUM). ALL OTHER DIMENSIONS ± 0.5 mm"

Advanced usage (with modifiers): If your "BF" actually means "B + Filter," you might add:

"EN ISO 13920-B, BUT FLATNESS OF MOUNTING FACE F1 (reference surface) TO BE HELD TO CLASS A (±0.5 mm)" These tolerances apply to external and internal lengths,

This notation tells the welder: "Use Class B for most features, but tighten up this specific surface."

Interpret as:

To truly understand "EN ISO 13920-BF," you must know the numbers. Below are the key tolerance ranges for Class B (Medium). "USE STANDARD WELDING TOLERANCES"

| Parameter | Requirement | |-----------|--------------| | Weld type | Butt weld, single V, or U with backing | | Backing location | Root side | | Backing material | Steel, ceramic, or permanent (specified separately) | | Dimensional tolerance | Class C (medium) or Class D (coarse) per EN ISO 13920 | | Inspection | Visual after backing, then after final weld |