There are mainly ultra-precision turning, mirror grinding and grinding. It is micro-turned on a super-precision lathe with a finely ground single crystal diamond turning tool. The cutting thickness is only about 1 micron. It is often used for the processing of spherical, aspherical and planar mirrors of non-ferrous materials with high precision and high surface roughness. Components. For example, an aspherical mirror with a diameter of 800 mm for processing a nuclear fusion device has a maximum precision of 0.1 μm and a surface roughness of Rz 0.05 μm.