trayraynor, Like I said, try a machinist's scribe-the kind that is used to do layouts on steel with machinist's blue. It is strong, but quite thin and comes to a fine point. With it, you might be able to chase out most of the thread. It sounds like your powdercoater used small tapered plugs, sort of like miniature rubber stoppers, which is typical. They might have been narrow and therefore went further into the hole than ideal and got painted over. They should come out pretty easily, leaving, perhaps, just a bit of fused powder that slipped through.