is a specific technical designation used in engineering drawings to define general tolerances for welded constructions. It combines two distinct precision levels from the ISO 13920 standard to ensure that welded parts fit together correctly without needing individual, complex dimensioning for every single weld. Breaking Down the Code: "BF"
This refers to the tolerance for straightness, flatness, and parallelism. While linear dimensions use letters A through D, shape and position tolerances use E through H. Class F is the second-most precise level in this category (often considered "Medium" for shape). Why Use EN ISO 13920-BF? en iso 13920-bf
Using this standard shorthand simplifies communication between designers and fabrication shops. Instead of calculating individual limits for every length and angle, a single note——applies a pre-defined set of rules based on the size of the component. is a specific technical designation used in engineering
This represents the "Medium" or "Mean" tolerance class. It is the most commonly used class in general engineering and steel construction. It provides a balance between functional accuracy and cost-effective fabrication. While linear dimensions use letters A through D,
This standard is widely used in machine construction , steel structures , rail vehicles, and shipbuilding. Tolerance Tables Overview
Specifying "Class B" avoids the high costs associated with the ultra-precise "Class A," while preventing the safety or assembly risks of the looser "Class C".