Ive never seen a nut that large with a hole that small in it. The nut is 22mm with a 5mm hole. This size nut usually takes about a 10mm bolt, plus it has that little slope on it. Where did you find this??
You can find them, but they are hard to find. The last tool I made was made from a 5/16" countersunk head allen bolt using two washers, a nut, and a plastic grommet that fit into the brass grommet. Works well, and if you go slow and swap the bolt around the other way after the initial "flare" has been made to finish the process, it usually won't split the grommet.