Sapphire single crystals have been ground by the ultra-precision surface grinder with various cup-type resinoid-bonded diamond wheels of #400-#3000 in grain size. The relationship between the surface roughness and grinding conditions has been clarified in the ductile mode. The smooth surface of sapphire single crystal less than 1nm rms or 1nm Ra in surface roughness can be obtained by the ultra-precision grinding without any polishing process.
