A microwave plasma technique has been employed to deposit polycrystalline diamond film over a molybdenum substrate button using a gas mixture of hydrogen and methane at a substrate temperature of 851 degrees C. A CVD diamond coated molybdenum substrate button was mounted with a load against hot nickel plate and rotated for 3.45 h in a hydrogen ambient. Hot tungsten filament was used as a heat source to maintain the temperature of the nickel block and CVD diamond coated molybdenum button at 848 degrees C. This experiment has reproducibly shown the successful polishing of polycrystalline CVD diamond by not nickel. A Tencor profilometer and scanning electron microscope have been used to evaluate the surface smoothness and morphology before and after polishing the polycrystalline diamond thin films.