Ok so I picked up some hardware. 1/2" steel zinc threaded rod , nuts, wing nuts and lock nuts. Should be able to basically slide the shaft in or out by unscrewing a wing nut when done. I removed the original axle and it appears to fit in fine.

Next I need to pull out the grinder and cut away the center post that is in the way and drill out all the holes the shaft will slide through to 1/2"