Diamond machining of materials for optical applications is becoming an important fabrication process. This report describes current development work in material-removal technology to better understand the mechanics of the diamond-turning process, its limitations, and applications. The technique is presently limited to a select group of metals, most of which are of a face-center-cubic crystal structure. Machinability studies were done which were designed to better understand diamond compatibility and thus expand the range of applicable materials. Nonconventional methods such as ultrasonic tool stimulation were investigated. Work done to determine the machinability of infrared window materials indicates that this is a viable fabrication technique for many materials, although additional effort is needed to optimize the process for particular materials.