En Iso 13920-bf Direct

In the context of EN ISO 13920, is not a tolerance class from the standard itself. Instead, it appears in welding symbols or technical notes to denote a specific weld preparation shape – typically Backing run with Flat face or Backing + Flat .

This class specifically governs the geometric tolerances of the weldment, including how straight a part is or how flat a surface must be. 2. Tolerance Tables for Class B (Linear & Angular) en iso 13920-bf