Because CNC machine tools are mainly used for small and medium-sized batch machining, and parts are frequently replaced, and the machining dimensions of parts are different, the materials of machining parts and tools are different, the difference between rough machining and finish machining, etc., therefore, different machining speeds need to be selected. Rough machining requires low speed and finish machining requires high speed; hard materials require low speed and soft materials require high speed. According to the range of parts processed by CNC gantry file milling machine, when drilling small holes or finishing (such as machining light alloy with bar milling cutter), the required rotational speed is the highest, while when filing large holes or aligning the cutter, the required rotational speed is the lowest. If the highest speed is 60 rpm and the lowest speed is 5 rpm, the speed range can reach 12 times.