En Iso 13920-bf Link

: Governs lengths, widths, heights, distances, and angular configurations. Class B represents a "medium" tolerance tier out of four classes (A, B, C, and D), striking a balance for structural frames, brackets, and machine housings.

This is the critical section for quality control.

Class F dictates the allowable deviations for . It specifically caps errors in straightness, flatness, and parallelism. Geometrical classes span from E (tightest) to H (loosest). Class F strikes a balance, offering standard structural alignment ideal for frames that interface with secondary components. Technical Tolerance Values Under Class BF en iso 13920-bf

If you see on a document, it is highly likely a typo or a non-standard internal code. It almost certainly implies Class B for linear dimensions. The "F" likely refers to a "Fine" requirement for geometry (which would make it ISO 13920-AD ), or it is a typo for D (making it ISO 13920-BD ).

: The tolerance class for shape and position (straightness, flatness, and parallelism). Typical Applications : Governs lengths, widths, heights, distances, and angular

This covers the "straightness" of the beam or the "flatness" of a plate. It ensures that while the part might be the right length, it isn't "banana-shaped" or twisted.

Stop guessing and start specifying. Are you using BF for your general steelwork, or do you prefer a tighter tolerance? Class F dictates the allowable deviations for

The standard uses a letter-code system to define four distinct tolerance classes. The code is actually a combination of two separate tolerance categories.

The most straightforward implementation is to add a note to the drawing's title block, such as . This clearly defines the baseline expectation for all dimensions not otherwise specified, removing ambiguity.

Do you have any specific questions about EN ISO 13920-1:2014 or HSS products in general? I'm here to help!