So like like old machines often do, this grinder turned out to have some hidden damage. In this case, the belt side was run with the tracking out of adjustment until the casting was cut completely through for about 90% of its length in the perfect shape of the belt. If not for the thick heavy duty casting, and a thicker mounting plate the tensioner bolts to, I suspect it would have already failed and blown apart in the face of the operator.
The drive wheel is very firmly stuck so for the moment I had to make this repair while the guard was on the machine. Welding that much cast iron, out of position with no pre/post heat control was a no go so I've settled on grinding out the cut and filling it with jb weld. I settled on Kwikweld as the strongest compound that would set fast and not flow out due to gravity.
At some point in the future this machine will get a full restoration and this will get cleaned up and possibly braze-reinforced in spots.
The first section filled:
Jb weld leaking through the back end of the cut:
