High Quality: En Iso 13920-bf
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 is an internationally recognized standard that provides a vital framework for quality control in welded structures. It applies to a wide range of industries, including steel construction, bridge building, crane manufacturing, shipbuilding, and general machinery.
If you saw "EN ISO 13920-BF" on a , it is likely a typo or shorthand used by a designer. The correct standard for edge preparations is ISO 9692-1 (or EN ISO 9692-1). EN ISO 13920 only covers general tolerances (linear, angular, flatness, etc.), not weld preparation shapes.
Table derived from data where class B angular tolerance is listed as 0.75°, 0.5°, 0.33° for ranges 0-400, >400-1000, >1000 respectively, converted to mm/m using the tangent of these angles. en iso 13920-bf
Tolerance depends on the length of the shorter leg of the angle.
The standard defines acceptable levels of variation for welded parts, thereby creating a common language between designers, fabricators, inspectors, and clients. This shared reference point helps projects run smoother, safer, and more efficiently by minimizing disputes and costly rework. Without such a standard, one fabricator might deem their work acceptable while the client insists on higher precision, often leading to delays and financial losses. By agreeing on ISO 13920 tolerances upfront, both parties share the same benchmark, reducing arguments and keeping projects on schedule.
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) Class F dictates the allowable deviations for
EN ISO 13920 is a European standard titled, "Welding — General tolerances for welded constructions — Dimensions for lengths and angles — Shape and position" . It is the European adoption of the international standard ISO 13920:2023, having been approved by CEN (European Committee for Standardization) without any modification. This standard is a critical tool in the manufacturing and engineering industries, as it specifies general tolerances for all welded structures, including weldments, welding assemblies, and other fabricated constructions.
| Tolerance Class | Typical Application | Cost Impact | | :--- | :--- | :--- | | | Precision machinery, jigs, fixtures | High (requires post-weld machining) | | B (Medium) | General mechanical structures, frames, supports | Optimal (achievable with standard welding) | | C (Coarse) | Heavy construction, shipbuilding, basic frames | Low (minimal inspection) | | D/E (Very coarse) | Simple structural steel, agricultural equipment | Very low |
: Class BF provides functional accuracy without demanding excessive precision. Demanding tighter tolerances (like Class A or E) requires expensive jigs, fixtures, and post-weld machining. Class F strikes a balance, offering standard structural
Thus, "EN ISO 13920-BF" signifies that the drawing is governed by the EN ISO 13920 standard. This means that all welded dimensions are to be manufactured to general tolerance (the standard medium precision for lengths and angles), while all applicable shape and position features must adhere to general tolerance Class F (a medium precision for geometry).
is widely considered the "standard workshop accuracy" class. It is the "Goldilocks" zone for general mechanical engineering—tight enough to ensure parts align during assembly but loose enough to be achieved by a skilled welder without specialized jigs or constant measurement. Practical Application
Under Class B, the permitted deviations for lengths, widths, and heights scale directly with the nominal size of the weldment. Smaller parts require higher accuracy, while larger assemblies are allowed more breathing room to accommodate cumulative weld shrinkage. Range of Nominal Sizes Class B Permitted Tolerance (mm) ±1plus or minus 1 Over 30 up to 120 ±2plus or minus 2 Over 120 up to 400 ±2plus or minus 2 Over 400 up to 1,000 ±3plus or minus 3 Over 1,000 up to 2,000 ±4plus or minus 4 Over 2,000 up to 4,000 ±6plus or minus 6 Over 4,000 up to 8,000 ±8plus or minus 8 Over 8,000 up to 12,000 ±10plus or minus 10 Over 12,000 up to 16,000 ±12plus or minus 12 Over 16,000 up to 20,000 ±14plus or minus 14 Over 20,000 ±16plus or minus 16 (Data sourced from ISO 13920 Workshop Guidelines ) Angular Dimension Tolerances (Class B)
