Advantages of focused ion beam (FIB) technology in micromachining are high feature resolution, capable of maskless processing, rapid prototyping, and adaptive for various materials and geometries. FIB was extensively used to fabricate a variety of microtools for ultraprecision machining and micromachining with typical dimensions ranging from 10 to 40 mu m and a curvature radius of 25 nm or even smaller. The microtools with controlled geometries, such as arc and sawtooth shapes, were shaped using FIB milling technique corresponding to different cutting requirements. The FIB milling is able to shape desired tool geometries with microscale features by means of controlling suitable ion beam parameters and precise orientation of the tools with respect to projection direction of ion beam. The cutting microtools used here are made from hard alloy. Testing experiments were carried out using a microtool with arc-shaped cross section to machine concentric rings and an annular plane in planar metal workpiece. Another microtool with sawtooth-shaped cross section was used to fabricate microdiffractive optical elements. The machining results demonstrated that the FIB-fabricated microtools can accurately machine desired microstructures. This fabrication method shows significant advantages of higher precision and lower cost than that of the conventional tool lapped finishing methods. It is promising to be an effective method for fabricating the microtools with complex shapes. (c) 2009 American Vacuum Society. [DOI: 10.1116/1.3054294]