Iso 13920-bf: En

| Wrong usage | Correction | |-------------|-------------| | "EN ISO 13920-BF" as tolerance class | Use C/D/E/F only. BF is weld prep code. | | Assuming BF means both tolerance and prep | Split into two references: ISO 13920 for tolerances + ISO 9692-1 for BF | | Using Class B | Not defined – switch to Class C if fine needed |

EN ISO 13920 is the international standard titled "Welding — General tolerances for welded constructions." en iso 13920-bf

Its primary purpose is to simplify technical drawings. Instead of adding individual tolerance values for every single dimension (length, angle, straightness), a manufacturer and client can agree on a general tolerance class. Unless otherwise specified, the dimensions of the welded structure must fall within the limits set by that class. | Wrong usage | Correction | |-------------|-------------| |

Before diving into the "BF" subclass, it is essential to understand the parent standard. EN ISO 13920 is the international standard titled

EN ISO 13920 (full title: Welding — General tolerances for welded constructions — Linear and angular dimensions — Shape and position) is the European adoption of the international ISO standard. It serves as a universal reference for permissible deviations in welded assemblies.

Unlike machining tolerances (which are very tight), welding tolerances account for the inherent variability of heat-based joining processes. The standard provides five distinct tolerance classes: A (fine), B (medium), C (coarse), D (very coarse), and E (extremely coarse). These classes allow designers to specify how much deviation is acceptable based on the function of the part.