CNC lathes all have spindle components, some have only one spindle component, and some have multiple. The machine tool spindle refers to the shaft that drives the workpiece or tool to rotate on the machine tool. It is a hollow stepped shaft. The hollow shaft occupies a larger volume of space, but can reduce weight. According to the material mechanics analysis, when the torque is transmitted by the rotating shaft, viewed from the radial section, the effect of transmitting effective torque is greater in the outer part. When the shaft needs to transmit a large torque, a thicker shaft diameter is required. And because the effect of transmitting torque at the center of the shaft is small, hollow is generally used to reduce the weight of the shaft. Spindle components are usually composed of the main shaft, bearings and transmission parts (gears or pulleys).

The motion accuracy and structural rigidity of the spindle components are factors that determine the machining quality and cutting efficiency. Indexes for measuring the performance of main shaft components are mainly rotation accuracy, stiffness and speed adaptability.

① Rotation accuracy: under the condition of no load and low speed, the radial and axial runout (see shape and position tolerance) mainly depends on the manufacturing and assembly quality of the spindle and bearing.

② Dynamic and static stiffness: It mainly depends on the bending stiffness of the main shaft, the stiffness and damping of the bearing. Insufficient static stiffness of the spindle will directly affect the machining accuracy and machine performance.

③ Speed adaptability: The maximum allowable speed and speed range are mainly determined by the structure and lubrication of the bearing, as well as the heat dissipation conditions.

The main shaft component is the executive part of the machine tool. Its function is to support and drive the workpiece or tool to complete the surface forming movement, and at the same time, it also plays the role of transmitting motion and torque, bearing loads such as cutting force and driving force.

Spindle aperture is also one of the factors affecting stiffness

The inner hole of the spindle is used to pass the bar and tool clamping device. It can also be used to connect the pneumatic (hydraulic) chuck (hollow pull rod). The larger the inner diameter of the spindle, the larger the diameter of the bar material that can be passed, the wider the range of use of the machine tool, and the lighter the spindle components. The diameter of the inner hole of the spindle is mainly restricted by the stiffness of the spindle. When the ratio of the bore diameter of the spindle to the diameter of the spindle is less than 0.3, the rigidity of the hollow spindle is almost the same as the stiffness of the solid spindle: when the ratio of the diameter of the bore of the spindle to the diameter of the spindle is 0.5, the rigidity of the hollow spindle is 90 %; When the ratio of the diameter of the spindle bore to the diameter of the spindle is greater than 0.7, the rigidity of the hollow spindle decreases sharply.