Spindles are electrically or air-powered devices that come in numerous sizes. Typically, there is a shaft that holds the tool together, a motor, and a taper used to control various tools. Then, the spindle rotates on an axis. The axis is controlled by commands coming from either a person or a computer.
Spindle is a rotating shaft with a fixture for holding a tool (in the case of a milling, grinding, or drilling spindle) or a workpiece (in the case of a turning spindle). The spindle shaft serves as a support, a positioner, and a rotary drive for the tool or workpiece.
Varieties of spindles include grinding spindles, electric spindles, machine tool spindles, low-speed spindles, high speed spindles.
CNC Machine Spindle
CNC Machine Spindle Design
CNC Machine internal design show in Picture above