an adaptive control system for a machine tool or the like includes two pairs of thrust sensors for measuring radial and axial spindle deflection and a temperature sensor for measuring spindle bearing temperature . data processing apparatus , typically comprised of a microcomputer , is coupled to the thrust and temperature sensors and regulates the spindle bearing preload and spindle axis feed rate in accordance with the radial and axial spindle thrust . the microcomputer simultaneously regulates the percentage of oil in the oil / air mixture lubrication mist sprayed on bearing contact surfaces in accordance with bearing temperature , thereby assuring optimum machine tool performance .