I made this set of snap-on soft jaws for my old Irwin 3″ clamp-on vise. (As of 2017 this vise appears to be sold as “Yost 3-in Cast Iron Vise” but don’t take my word for it.) It includes a horizontal notch for holding dowels or threaded rod. Just snap them on when needed. (The jaw profile is asymmetrical on this vise, so the 2 soft jaws are slightly different.).