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".
"USE STANDARD WELDING TOLERANCES"
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" en iso 13920-bf
The permissible deviation (in millimeters) for linear dimensions such as lengths, widths, and heights. As the nominal dimension of the part increases, the allowable tolerance increases correspondingly.
The ISO 13920 international standard regulates dimensional deviations in welded assemblies, frames, and steel structures. When metal is subjected to the intense heat of structural welding, it undergoes thermal expansion and contraction, naturally causing a degree of warping and misalignment. Specifying "Class B" avoids the high costs associated
: Guarantees that parts fabricated in different shops or by different welders will fit together seamlessly during final assembly.
(lengths and angles). Class B is generally considered "medium" or standard workshop accuracy. : Refers to the tolerance class for shape and position Breaking Down the Code: "BF" The permissible deviation
Symmetry tolerance (Class B = up to 3 mm) is not the same as coaxiality of bores. For two bores that must align for a shaft, use a separate geometric tolerance (GD&T), not ISO 13920.
The first letter denotes the allowed variance for overall sizes, distances, step configurations, and intersecting weld corners. The standard defines four classes: : Fine B : Cool/Medium C : Coarse D : Very Coarse.
Understanding EN ISO 13920-BF: The Standard for Welding Tolerances
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".
"USE STANDARD WELDING TOLERANCES"
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"
The permissible deviation (in millimeters) for linear dimensions such as lengths, widths, and heights. As the nominal dimension of the part increases, the allowable tolerance increases correspondingly.
The ISO 13920 international standard regulates dimensional deviations in welded assemblies, frames, and steel structures. When metal is subjected to the intense heat of structural welding, it undergoes thermal expansion and contraction, naturally causing a degree of warping and misalignment.
: Guarantees that parts fabricated in different shops or by different welders will fit together seamlessly during final assembly.
(lengths and angles). Class B is generally considered "medium" or standard workshop accuracy. : Refers to the tolerance class for shape and position
Symmetry tolerance (Class B = up to 3 mm) is not the same as coaxiality of bores. For two bores that must align for a shaft, use a separate geometric tolerance (GD&T), not ISO 13920.
The first letter denotes the allowed variance for overall sizes, distances, step configurations, and intersecting weld corners. The standard defines four classes: : Fine B : Cool/Medium C : Coarse D : Very Coarse.
Understanding EN ISO 13920-BF: The Standard for Welding Tolerances
