Abstract: A closed hydraulic system for band saws transmits manually actuated control of the saw blade tension, provides for easy and remote reading of blade tension, instantly stops rotation of the upper saw blade wheel in case of blade breakage, shuts off the motor drive when blade breakage occurs, and prevents restarting of the motor until a new blade is installed and tension is applied thereto. The upper idler blade band wheel is equipped with a spring loaded brake held in a non-braking position by hydraulic fluid which is pressurized from a manually actuated crank which shifts the upper wheel to apply tension to the saw blade band and when the band breaks to release the tension, the fluid pressure drops sufficiently to allow the springs to actuate the brake for stopping the wheel. At the same time, a fluid pressure actuated switch in the electric circuit for the driving motor is opened to prevent restarting of the motor until tension is once again applied to a new saw band.