For lead screw nut, use 932 or 660 bearing bronze, much easier to cut and thread. You get a better wear ratio, giving you little wear to the screw thread vs the nut. 954 will hold up longer with little wear, but will wear out your lead screw by the time a new nut is needed. And will give you grief trying to machine it at times. Amco 18 is ideal but very expensive and hard to get.