A milling machine has a carriage, a main spindle seat extending along an axis, and a motor operable to drive displacement of the main spindle seat relative to the carriage along the axis. A deflection correction system includes a control unit, a displacement sensor, at least one pressure cylinder, and a pressure sensor. The pressure cylinder includes a cylinder body, and a control rod extended retractably into the cylinder body. The control unit is configured to determine a pressure range as a function of displacement detected by the displacement sensor, and to maintain fluid pressure in the pressure cylinder within a pressure range, thereby controlling the control rod via the cylinder body to position the second end portion of the main spindle seat relative to the axis.