Guide bush and method of forming diamond-like carbon film over the guide bush

A guide bush substantially in a cylindrical shape, having a center bore penetrating through the entire length thereof along the longitudinal axial direction, said guide bush comprising:

• an outer taper surface and slots for providing elasticity thereto, formed at one end thereof in the longitudinal axial direction;
• a threaded section formed at the other end thereof for being attached into a column of an automatic lathe;
• and
• an inner surface for holding a workpiece, formed at the inner radius of a portion where the outer taper surface is formed, wherein the workpiece inserted in the center bore is held by the inner surface rotatably and slidably in the longitudinal axial direction in close proximity of a cutting tool, when the guide bush is attached to the automatic lathe, the inner surface is provided with a cemented carbide alloy containing at least cobalt and an intermediate layer is formed over the cemented carbide alloy while a diamond-like carbon film is formed over the intermediate layer, cobalt contained in the surface of the cemented carbide alloy adjoining said intermediate layer being removed therefrom,
• wherein marks caused by a grinding process are removed from the surface of the cemented carbide alloy adjoining said intermediate layer, and
• wherein the surface of the cemented carbide alloy adjoining said diamond-like carbon film is not specula but has rough finish.