Just a thought but you could get a new shaft. Take the large part of your broken shaft to a machine shop, have them clean up the break and cut keyway slots in the old piece and the new shaft. Then you install the old drive part on the new shaft. Just a thought but either way I would take the shaft to a local machine shop and see what they think. They just may have a better idea than all of us being as they do stuff like that all the time.
P.S. Cast iron can be welded. We would use Nicad rods, a torch for preheating and a ballpeen hammer to ping the weld after every rod. Admittedly this was usually just for skin casing on boilers and nor for anything under pressure or being torqued in any way.
Everything i build comes with a redneck warranty. If it breaks you get to keep both pieces.
Last edited by Mikhail2400; 08-10-2018 at 11:57 AM.