I sold a craftsman table saw with a cast iron top having the same
trouble, the fella I sold it to was an auto mechanic who took the
table off and took it to an auto machine shop that had a wide belt
sander for flattening automotive machine heads. Cost him $15 worked
like a charm according to him. I do think he followed that up with
some 600 grit and a nice wax job to complete it.

EJ