The ultra-precision machining process using a single crystal diamond tool has been mainly used for machining molds of optical components. Since the micro patterns of various shapes having excellent surface roughness can be machined by using ultra-precision machine tools, the micro pattern on a large light guide plate (LGP) is mainly machined using a diamond tool. The tool wear occurs due to long machining distances and time while machining a large-area LGP mold. The deformation and dimensional error of micro pattern are caused by tool wear, as a result, the light efficiency of LGP declines. The characteristics of tool wear should be analyzed in order to precisely machine large-area LGP mold from all sorts of materials. The experiments were performed in order to compare wear characteristics of a V90° diamond tool using Al3003, 5052, 6061 and 7075. The prism pattern of depth 10 μm was machined in order to analyze characteristics of tool wear according to machining distances (0.5, 1 and 1.5 km). The effects of tool wear on pattern shape were analyzed by applying overlapped cutting depths (Rough machining is (10+8+7) μm and Finish machining is (5+3+2+1) μm) by continuously machining a prism pattern of W shape of 25 μm in depth.