Abstract: A device employed with a vibratory apparatus such as a mill or the like which is used to change the lead angle between rotating eccentric weights. Eccentric weights are mounted at either end of a drive motor and caused to rotate with the motor shaft at specific angles with respect to one another to develop a specific vibratory action. At one end, the eccentric weight is fixedly mounted on the shaft. At the other end, the weight is rotatably mounted on the shaft. A stop mechanism is associated with the shaft adjacent the rotatably mounted weight to prevent the weight from pivoting through more than a predetermined angle. By rotating the motor and shaft in a first direction, the rotatably mounted weight assumes a position on the shaft at a first stop. When the motor is reversed, the rotatably mounted weight swings to a position at a second stop.