Focused ion beams (FIBs) have found a place in several research thrusts for the manufacture of mini or micro mechanical objects. This article reports the use of FIB in three distinct applications in microfabrication: prototype structures, micron-sized machine tools and microsurgical manipulators, and ion milling of three dimensional features. Examples of each of these applications are given with the FIB component identified as the enabling or critical component in the technology. The possibility of using FIB milling as part of a production method for micron-sized machine tools is discussed, and the mass production consequences of molds fabricated by three dimensional ion beam milling is also considered. The mathematical procedure and programming steps needed to accurately control FIB three dimensional milling are outlined.