I have an old grinder that I am debating changing out the shaft for a longer one. Any suggestions on where or what to look for? This is an independent grinder that is belt driven so no motor problems. I have seen mention of getting drill bit shank? Currently it is 3/4 on the ends and slightly larger in the center that allows for easier time punching out the ball bearings.

If pictures would help just let me know. Currently it is all apart, finally, it took multiple days to break down such a small grinder hub due to years of use.