I'm copying from a closed thread that ALMOST answers my question perfectly...
"weavedreamer (Automotive)14 Jul 15 13:10
Per ASME:
Flatness comes into play in with the "To or Thru Rule".
1) If the stack goes to a surface, the form of the surface must be accounted for in the stack.
2) If the...
I have a plastic part which is injection molded, then subsequently R.F. Welded. One area of the part has fairly thin sections which is where the welding will eventually occur.
We call out a nominal thickness of .030" +/- .005"
The welding operation is not tolerant of SUDDEN changes in...