Main shaft structure of numerically-controlled machine tool

The invention provides a main shaft structure of a numerically-controlled machine tool. The main shaft structure comprises a cutter bar connected with a main shaft and a cutter bit connected with the cutter bar. The head of the cutter bar is inserted into the main shaft. The tail of the cutter bar is in an inverted-tapered shape, the tail is connected with the cutter bit, and the specific value of the diameter of the end of the tail and the diameter of the cutter bit is smaller than or equal to 1.7:1. The specific value of the diameter of the end of the main shaft and the diameter of the head of the cutter bar is smaller than or equal to 1.5:1. The taper of the head of the cutter bar is smaller than or equal to 2 degrees. The taper of the tail of the cutter bar is smaller than or equal to 10 degrees and larger than or equal to 3 degrees. The specific value of the length of the tail of the cutter bar and the length of the portion, exposed out of the cutter bar, of the cutter bit is smaller than or equal to 2.5:1. The surface of the cutter bit is covered with an ultramicron layer. The main shaft structure has the advantages of being simple and reasonable in structure, flexible to operate, high in working efficiency and long in service life.