Since the 1970 's, a large number of man-made abrasives have been produced, of which the most important are silicon carbide and alumina two kinds. Silicon carbide commonly known as Emery, will be pure silica sand mixed with coke to add a small amount of sawdust, into the electric furnace, in 2,200~2,480℃ roasting about 36 hours and made. Alumina, commonly known as corundum, is commonly used in industrial arc furnaces to heat molten bauxite, which is made of white and transparent as a thermally sensitive metal, and is used for processing castings and steels. The man-made diamond grinding wheel is the most hardness abrasive, which is necessary for the grinding of cemented carbide tools. Synthetic diamond can also be made into a variety of shapes and sizes of tools to apply to cutting glass and ceramics. The hardness of boron carbide is higher than that of silicon carbide, it is not suitable for making grinding wheel, it can be used to replace expensive diamond when polishing hard material. Cubic boron carbide is twice times the hardness of silicon carbide, 2.5 times times that of alumina, which is useful for grinding certain tool steels.