Managing tolerances Precision sheet metal has many variables that effect tolerance, shape, size, and features. For example, sheet thickness tolerances from a mill can vary from +/-.0035 on the most used gages, which are 14-20 gage (.074” – .036”) to +/-.0075 on the thicker gages. A common issue to watch is designs with zero clearance between parts. This can create a tolerance stack up, resulting in parts that will not fit during assembly. When assemblies are modeled, the tolerance of the parts should be accounted for in the spacing of the parts to be sure they will fit together when assembled. Tooling considerations The tooling required to make a part can limit that part’s shape. Conventional press-brake tooling, for example, allows for precision straight-line bends that can be fitted to almost any length and are typically used on most fabricated sheet metal parts. Keeping designs in this shape area allows for lowest cost and fastest manufacturing times. This holds true for features like round embosses, bridge lances, countersinks, extrusions, or other features. These can be typically done in a punch press and every effort should be made to stay with standard sizes when possible...