Precision and micro CVD diamond-coated grinding tools

Both for ultra-precision and for micro-machining diamond is used very often as tool material. The reason is the very high dimensional stability of diamond due to its extreme hardness. Diamond is used for two kinds of machining processes: for cutting, like turning, drilling or milling, as well as for abrasive processes, like grinding. Diamond cutting tools can be made with massive diamond (monocrystal, CVD diamond, PCD) or with diamond coatings. Standard diamond abrasive tools are made by bonding diamond monocrystals onto a base body. A new grinding layer technology is presented: chemical vapour-deposited microcrystalline diamond layers have crystallite tips with very sharp edges that can act for grinding processes. Base body materials and coating technology is presented. Application results of grinding experiments show that very high workpiece quality can be reached, e.g. a roughness Ra of 5 nm with glass workpieces. Truing and recoating techniques are discussed for reuse of worn CVD diamond grinding wheels. Micro grinding tools (abrasive pencils, burrs) can be manufactured with the same coating technology. Very small tools with diameters of 50 μm have been made and successfully tested.