In Reply to: Need help posted by Thad on June 24, 2019 at 15:29:35:
On any machine this old the original size may have been messed-up so bad it was drilled out and tapped some larger size. Maybe a previous owner tried to fit a water temp gauge fitting in the drain hole. I keep a small assortment of fittings in bins mostly so I can match up threads before starting to look for parts. There are some thread charts on-line that can be used to figure out thread sizes if you don't have a selection of fittings sorted.