Welded assemblies move under heat input; machined parts can hold tight feature-to-feature relationships when fixtured predictably. Mixing both on the same critical interface requires careful datum planning.
If you need a machined bore pattern to align after welding, specify whether post-weld machining is allowed and which surfaces establish the final datum scheme.
Weld symbols should reference acceptable processes and inspection (VT, PT, etc.) when structural integrity is regulated.
Communicate “as-welded” vs “machined after weld” clearly—quotes depend on which side of the process owns the tolerance stack.