In order to overcome the self-excited vibrations in internal turning (chatter) a new design for boring bar, which depends on using steel-balls to support boring bar system [1]. The steel balls system increases the stiffness’s of both boring bar and workpiece. The pressure of the pressurized oil used in this system has a noticed effect on the self-excited vibrations. In the present paper, a gear pump driven by a DC motor system is designed to control the pressure. The oil of this system is pumped to the boring bar with low pressure to decrease the tendency of the system to chatter. The pump-motor system model was created in MATLAB/ SIMULINK simulation and then PID controller parameters designed to control the pressurized oil for keeping it less or equal 4 bars to save these lf-excited vibrations within the desired limits. The PID parameters were optimized by the Genetic Algorithm (GA). The algorithm gave the desired pressure in a noticed small time.