Some antiques I was restoring had attachment with similar fitments. I got rid of some of the roughness with emery without sanding down the residual stud. After that I took some thin wall brass tubing from the hobby shop of the "just" right id to fit over the stud and epoxied it on. after all set up I thinned down the od of the tubing just a bit with emery and slightly enlarged the id of the self threading nuts with an awl and ran them on.