Sheet Metal Design Sheet Metal Design Design Resources Tolerances Sheet metal tolerances should not be tighter than necessary to make the part functional.
Tight tolerances raise the cost of manufacturing significantly.
Practical tolerances vary according to the design requirements. Linear tolerances should be held as loose as possible. Flatness Flatness specifications are applied with perfect form not required at maximum material condition. In general the primary datum should have some type of form specified. Defining the primary datum by datum targets in a retrained condition is preferred.