Hydrostatic nut and lead screw assembly, and method of forming said nut

Abstract

A method of forming a hydrostatic nut that cooperates with a lead screw for translating a wheel head, or carriage, on a grinding machine, such as a cam grinder. A lead screw standard, or master, which is externally threaded, is inserted into a cylindrical mold, which is internally threaded. The standard is retained therein by pressure plates that seal off opposite ends of the open bore of the mold. Beads of wax, or tape, or some other rigid instrumentality, are adhered to the exterior surfaces of the helical threads on the standard, while the rest of the standard is treated with a release coating. A continuous cavity is defined between the internal threads on the nut and the external threads on the standard. An epoxy resin or other castable polymer is introduced through an inlet port in the mold into the cavity. The castable polymer is allowed to cure into a rigid mass that adheres to the internal threads on the mold except for the helical beads. The standard is removed, the mold is machined to its final configuration as a hydrostatic nut, and the wax, or tape, is removed to leave voids in the rigid cured polymer. The voids define oppositely directed helical channels that are pressurized to form a thin fluid film that prevents metal to metal contact between the complementary helical threads on the nut and lead screw. The cured polymeric mass is structurally reinforced by the threads defined on the metal nut, so that the channels defined on the exterior surface thereof maintain their dimensions.