the spindle protruding refers to the distance design from the front end face of the spindle to the front support (usually the middle point of the front radial support), which is mainly the middle point of the radial reaction force determined by the structure. However, a value has a great influence on the stiffness and vibration-resistant spindle parts, so when determining the value, the value should be as small as possible to meet the structural requirements. The main shaft of xk2116 CNC gantry boring and milling machine is 0.1 M. according to the structure requirement Its structural layout has the following characteristics: