Practical example: A 200 mm long corner joint allowed deviation is approximately ±1 mm measured at the tip.
To fully appreciate Class D, one must examine its specific numerical limits across three critical parameters: linear dimensions, angular dimensions, and shape/position (flatness, straightness, parallelism). iso 13920-d
The standard categorizes welded structures into five tolerance classes: . These range from very fine (Class A, typically for precision machinery) to very coarse (Class E, for massive steel structures like bridges or ship hulls). Class D , the subject of this essay, sits in the middle-lower range of the spectrum. It is best described as the “standard commercial” tolerance class. It is neither precision engineering (Class A/B) nor rough construction (Class E). Instead, ISO 13920-D applies to general fabrication where fit-up is important, but where post-weld machining is not anticipated. Practical example: A 200 mm long corner joint
The engineering team reviewed the functional requirement. The crane end trucks could accommodate up to 20 mm of misalignment. They re-specified to ISO 13920-D , which allows 19 mm over 8-12 meters. These range from very fine (Class A, typically