Cast iron is easy to thread- - - - -just don't try to use a SAE (fine) thread for any particular size bolt. Coarse (UNF) threads work best in cast iron applications.
Jerry
FYI, Coarse threads are designated UNC - for Unified National Coarse) not UNF. SAE threads are measured in inches as opposed to metric, and include fine and coarse patterns. Fine SAE threads are designated UNF.
But Jerry is correct that coarse threads should be used in cast iron.
