I have the X and Y ballscrews and nuts for a Milltronics knee mill. It is Willis iron made in 1996. The screws are used, with .004 error per inch. 50.00 each, OBO, pickup near Kalamazoo Mi, or I can put them in the crates the new ones came in and ship them. No attempts have been made to rebuild them or determine the cause of inaccuracy.