Abstract of research: It is well known that a diamond tool will be worn severely when cutting process is performed to ferrous material by a diamond tool. The purpose of this research is to develop a three dimensional micro machining method for a diamond by utilizing this phenomenon. The experiment is conducted by a lathe, where a ferrous material rod is fixed at the chuck of the lathe, and a single crystal diamond is fixed on top of a shank in the tool post of the lathe. A screw pattern is given to the external surface of the ferrous material rod and the feed rate during cutting process is made into the same value as the pitch of the screw. By this process, the pattern of screw can be transferred on the diamond surface. From the above experiments, the following conclusions can be obtained. 1. A diamond can be machined by this method 'irrespective of the crystallographic orientation. 2. The removal rate of diamond is the largest in (1,1,0) plane, and it is the smallest in (1,1,1) plane. 3. The cutting temperature degree during the process is effective on the removal rate of diamond. 4. The machined surface by this method is much better than that one by YAG laser machining. The machining removal rate by this method is better than that by other rubbing method. 5. The process of this machining is investigated by measuring the cutting force, the machining temperature and the actual depth of cut.