2. Material and methods 2.1. Single-grit tool fabrication and specimen preparation A natural diamond that was pyramid-shaped with a tip radius of approximately 20 μm was welded on the front end of the tool, as shown in Fig. 1. Then, a focused ion beam (FIB) system was used to fabricate a sharp pyramid shaped tool tip on the top end of the natural diamond, as shown in Fig. 2(a). The tool tip has a regular pyramid shape with a square cross section and has dimensions of 20 20 10 μm, as shown in Fig. 2(b). The tip radius is smaller than 1 μm. A commercially popular leucite glass–ceramic was selected for use in this study.