Geometrical rules ensure that components stay flat, straight, and properly aligned with interacting components. Class F parameters are determined based on the of the relevant surface or edge.
Understanding the standard requires isolating the two distinct tolerance classes combined within the "BF" identifier:
For linear measurements, Class B dictates the following permissible deviations: ±1 mm Over 30 mm to 120 mm: ±1 mm Over 120 mm to 400 mm: ±2 mm Over 400 mm to 1000 mm: ±3 mm Over 1000 mm to 2000 mm: ±4 mm Over 2000 mm to 4000 mm: ±6 mm Over 4000 mm to 8000 mm: ±8 mm Over 8000 mm to 12000 mm: ±10 mm Over 12000 mm to 16000 mm: ±12 mm Over 16000 mm to 20000 mm: ±14 mm Over 20000 mm: ±16 mm Angular Dimensions en iso 13920-bf
Therefore, signifies that a welded structure is built according to intermediate quality standards for both dimensional accuracy and structural shape. Core Components of EN ISO 13920-BF
: Represents the tolerance class for linear and angular dimensions . Class B is considered "medium" or "customary workshop accuracy". Core Components of EN ISO 13920-BF : Represents
Raising the baseline temperature of the base metal minimizes the localized thermal shock caused by the welding arc.
| Class | Typical use | |-------|--------------| | | Fine – machined parts, precise jigs | | D | Medium – general structural steelwork | | E | Coarse – large fabrications, shipbuilding | | F | Very coarse – flame-cut plates, heavy beams | | Class | Typical use | |-------|--------------| |
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.
: Represented by uppercase letters (E, F, G, H).