General Metal Sheet Tolerance

Fifty years ago sheet metal tolerances were about +/-.06" (1.5mm). Today they are approximately 10% of that, or +/-.006" (.15mm). As a general design practice, you should consider the tolerance to be +/-.010". If you are looking for more information on this subject, ASTM A 176 details the standard specification for general requirements for flat-rolled stainless and heat-resisting steel plate, sheet, and strip.