Abstract: An improved precision lead screw and nut assembly, including an improved nut, includes a nondeformable screw member having a helical thread on the exterior thereof, the thread being formed by a rib having a crest, adjacent side walls, the rib defining a helical groove having a root which is located between the side wall of adjacent crests. The screw cooperates with a housing, the nut being positioned within the housing and cooperating with the screw such that relative rotation between the nut and the screw causes translational movement between the two. The nut includes a helical thread formed by a rib and adjacent side walls, the rib defining a helical groove having a root located between the side walls of the adjacent crests of the nut. The nut is preferably formed of a thermoplastic base material such as an acetal resin containing finely divided particles of a fluorocarbon resin such as polytetrafluoroethylene uniformly distributed throughout the base material.

Abstract: A tapered gib for use in machine tools is composed entirely of a plastic material such as an acetal resin containing uniformly dispersed, finely divided particles of polytetrafluoroethylene so as to provide reduced friction. The surface of the gib in contact with the associated table and positioned between the saddle and the table is formed with raised portions forming the contact surfaces. Various forms of raised surfaces may be used including nibs, ridges and the like. The gib, by virtue of the material of which it is made, fits better, may be operated without lubrication and offers the advantage that it wears relatively slowly and in preference to the metal components with which it is in sliding contact. When worn, the gib may be easily replaced and the new gib easily adjusted since it can be stressed to fit the way in the table with a minimum of deforming creep and short of taking a permanent set by virtue of the compressive forces encountered.