Diamond is a allotrope of carbon, a material which is found in nature has been the hardest. Diamond tool with high hardness, high wear resistance and high thermal performance, are widely used in the processing of non-ferrous metals and non-metallic materials. Especially in high-speed cutting of aluminum and silicon aluminum machining, diamond tools are difficult to replace the main varieties of cutting tools. Can achieve high efficiency, high stability, long life and processing of diamond tools is an important tool for modern CNC machining indispensable.     ⑴ types of diamond tools       ① natural diamond tools: natural diamond as a cutting tool has been a century of history, natural single crystal diamond tool after fine grinding, can be worn extremely sharp edge, edge radius of up to 0.002μm, to achieve ultra-thin cutting, can high precision machined workpiece and low surface roughness, is recognized as the ideal and not a substitute for the ultra-precision machining tool.       ② PCD diamond tools: natural diamond expensive diamond is widely used in cutting or polycrystalline diamond (PCD), since the early 1970s, the use of high temperature and high pressure synthesis technology to prepare polycrystalline diamond (Polycrystauine diamond, referred to the successful development of PCD inserts later, in many cases natural diamond tools have been replaced by synthetic polycrystalline diamond. PCD rich source of raw materials, only a few tenths of one to ten fraction of natural diamond price.       PCD tools can not grind extremely sharp cutting edge, the surface quality of processing is not as natural diamond industry today can not be easily manufactured with PCD inserts chipbreaker. Thus, PCD only for non-ferrous metals and non-metallic fine cut, is difficult to achieve ultra-precision mirror cutting.       ③ CVD diamond tools: Since the late 1970s to the early 1980s, CVD diamond technology in Japan appear. CVD diamond is the chemical vapor deposition (CVD) in a heterogeneous substrate (such as cemented carbide, ceramic, etc.) synthetic diamond film, CVD diamond structure and having the same characteristics of natural diamond. CVD diamond's performance compared with the natural diamond is very close, both natural advantages of single-crystal diamond and polycrystalline diamond (PCD), to a certain extent, but also overcome their deficiencies.