Got this little idea the other day and had a buddy turn it out of 3/4 in brass round stock. It allows me to chuck it in the headstock, put a brass tube on the lathe for ruffing up the surface and then use the same drive to hold one of the bushings for turning the actual segment of the pen. The little hole in the center of the point zeros up the error, if any . Filing the jaws true while turning slowly helps validate the surface for the flange to rest against.