Method of forming hard carbon film over the inner surface of guide bush

Abstract

A hard carbon film is formed in a vacuum vessel directly or through an intermediate layer for enhancing adhesion over an inner surface of a guide bush with a uniform thickness and excellent adhesion wherein the inner surface is in sliding contact with a workpiece and the guide bush is mounted on an automatic lathe for holding the workpiece rotatably and slidably in the axial direction near a cutting tool. Accordingly, the method comprises disposing the guide bush in a vacuum vessel, inserting an auxiliary electrode into the center bore forming the inner surface of the guide bush to be at a ground potential, introducing a gas containing carbon into the vacuum vessel through the gas inlet port after evacuating the vacuum vessel, and applying a DC voltage to the guide bush through a reactor, thereby producing a plasma in the vacuum vessel so that a hard carbon film of hydrogenated amorphous carbon is formed over the inner surface of the guide bush by a plasma CVD method.