General tolerance ISO 2768 does not specify where to use these tolerances. You should define tolerance class as per design requirements and manufacturing capability. For example, the manufacturer recommends ISO 2768-mk for sheet metal parts and ISO 2768-fh for machined components. In the above example, “m” and “k” have defined the tolerance class.

You can calculate the critical dimension tolerance using tolerance stack-up analysis. You can also use a tolerance stack-up calculator for this purpose.

It is not possible to define engineering tolerances against each dimension. Therefore engineers define general tolerances in engineering drawings to define the variation. ISO 2768 standard defines general tolerance for:

We suggest you read this article on go-no-go gauges.