In this paper, experimental results about the speed stability of one shaft operating by using the hydraulic motor with proportional valve are presented. Exclude the elastic deformation of the transmission belt. Besides, the mathematical model and fuzzy self-tuning PID controller is introduced. In the model, the V-belt is assumed as an elastic module and the friction coefficient and mass inertia moment of the hydraulic motor can be considered as constant. The Matlab is used to simulate the speed response of the hydraulic motor to the working shaft. The main parameters for the experimental investigation are setting time, overshoot and error of rotation at the steady state. So, speed stability of the working shaft operating by the hydraulic motor which is controlled by the proportional valve with the fuzzy self-tuning PID controller. Based on our findings, we propose the applicability on the main shaft of the metal cutter.