DIN 8570-1:1987-10

It specifies general tolerances for linear and angular dimensions of welded structures in four tolerance classes, these being based on customary workshop accuracy. The main criterion for the selection of a particular tolerance class should be the functional requirements which are to be met. If smaller tolerances are required, or if larger tolerances are both permissible and more economical, then they shall be indicated individually in accordance with DIN 406 Part 2.