13920-bf Portable — En Iso

The suffix tells the manufacturer exactly which tolerance "bracket" to use for different types of measurements:

(For the sake of this post, we will assume the user implies a requirement, which is standard Class BD , or is asking about the specifics of Class B ). en iso 13920-bf

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

| Nominal Size (mm) | Permitted Flatness Deviation (Class B) | | :--- | :--- | | Up to 120 | 1 mm | | 120 to 400 | 1.5 mm | | 400 to 1,000 | 2 mm | | 1,000 to 2,000 | 2.5 mm | | 2,000 to 4,000 | 3 mm | | 4,000 to 8,000 | 4 mm | | > 8,000 | 5 mm | It defines the allowable deviation for measurements like

This is the "Medium" class for lengths and angles. It defines the allowable deviation for measurements like the length of a beam or the degree of an angle.

| Tolerance Class | Typical Application | Cost Impact | | :--- | :--- | :--- | | | Precision machinery, jigs, fixtures | High (requires post-weld machining) | | B (Medium) | General mechanical structures, frames, supports | Optimal (achievable with standard welding) | | C (Coarse) | Heavy construction, shipbuilding, basic frames | Low (minimal inspection) | | D/E (Very coarse) | Simple structural steel, agricultural equipment | Very low |