: 1/2" & 5/8" Tapered Spindle Adapter Threaded ...
→1st, remove the outer guard, grinding stone and inner guard on bench grinder; 2nd, fix spindle adapter to grinder shaft with grub screw. Kindly note: one adapter provide one screw, it's tight enough to fix the spindle adapter to grinder shaft as per our factory's test, the balance 2 holes are auxiliary for mount and demount adapters.