Fabrication tolerance

Fabrication tolerance is the permitted deviation of a fabricated hull part from its nominal dimension, straightness, flatness, alignment, or angularity, set by the yard’s quality acceptance standard so the structure stays within the strength and fit-up assumptions of the approved drawings. The reference framework is IACS Recommendation 47 (Shipbuilding and Repair Quality Standard for New Construction), which tabulates standard and limit ranges for plate misalignment, weld profile, distortion, and block dimensions. A deviation inside the standard range is accepted; beyond the limit range it is rejected and reworked; the band between is repaired by agreement. Tight tolerances control distortion, fit-up, and the locked-in stress carried into service.