: Represents the tolerance class for shape and position (such as straightness, flatness, and parallelism). Tolerance Tables for EN ISO 13920-BF
For a length of 1 meter, the allowed deviation is approximately ±2plus or minus 2 Covers straightness, flatness, and parallelism. en iso 13920-bf
(straightness, flatness, and parallelism). Class F is often used for structural assemblies where moderate precision is required. Summary of Tolerances : Represents the tolerance class for shape and
The classes are independent of each other, meaning a drawing can call for a high-precision size (e.g., class B) while still allowing for a wider tolerance on shape (e.g., class F). This is exactly what the combination signifies: class B for dimensions (lengths & angles) and class F for geometry (shape & position) . The specification ISO 2768-mk is used for a similar purpose but for machined parts, while ISO 13920-BF is used explicitly for welded constructions . Class F is often used for structural assemblies
If you need the exact for such a preparation (e.g., root face, gap), that would be found in ISO 9692-1, not ISO 13920.
The suffix tells the manufacturer exactly which tolerance "bracket" to use for different types of measurements: