I too have many grinders set up for specific duties. One grinder I have set up with diamond lapidary plates. I use them for everything and have many different grits for the job. You’d have to make a hub backing plate but they work phenomenal. I made the backing plate out of a pc of aluminum 1/4 thick.
As for the SG problems that doesn’t look to bad to fix. If that were me I would replace the top piece that’s broke with a chunk of steel. Machining should be difficult. Looks like a rectangle block that should have some recessed mounting holes to bolt to the vertical upright. Then I’m sure there is a bore in the center for a cup and race bearing. Pretty basic machining. With the crack probably being around the bearing bore I wouldn’t recommend jb weld. If above your skill you can always remove and send it out to be duplicated. I’d be open to help if need be. Good luck.
As for the SG problems that doesn’t look to bad to fix. If that were me I would replace the top piece that’s broke with a chunk of steel. Machining should be difficult. Looks like a rectangle block that should have some recessed mounting holes to bolt to the vertical upright. Then I’m sure there is a bore in the center for a cup and race bearing. Pretty basic machining. With the crack probably being around the bearing bore I wouldn’t recommend jb weld. If above your skill you can always remove and send it out to be duplicated. I’d be open to help if need be. Good luck.