A saw has a system for sensing the torque on a cutting blade to signal when the blade begins to cut material. The saw has a drive belt extending between a driven wheel and a drive wheel and a belt tensioner that engages a side of the belt and maintains tension in the belt. The belt tensioner is movable to maintain the tension in the belt. A control system calculates the movement of the belt tensioner. The saw has a system for determining the size of the sacrificial blade. A through beam photoelectric emitter and receiver pair are positioned on opposite sides of the blade such that a largest cutting blade is moved above the beam regardless of a horizontal position of the cutting blade and sensor senses a vertical position of the axis of the blade. The sensor senses the vertical position of the blade axis when the blade is moved above the beam.