Abstract: Window sashes such as double hung sashes often are assembled with a counterbalancing mechanism to facilitate the opening and closing of the window. When the sashes are made from vinyl, the counterbalancing of the window is commonly achieved by the use of a pair of coil springs, one mounted within a channel in the sash on either side of the window. A programmable motorized hand tool is used to apply tension quickly to each of the springs thereby improving production rates and quality control while reducing the risks of repetitive motion injury to the person using the hand tool. A programmable stepper controller drives the motor and controls the functions of the hand tool such as the speed and direction of rotation, the number of revolutions and the start-up and operating torques.