From grade school math you may remember that a 2″ circle will have a 1″ radius, a 1″ circle will have a 1/2″ radius, a 3/4″ circle will have a 3/8″ radius, etc… The diamond dresser tool on your Wissota 911 Machine will dress (shape) the face of your grinding wheel to the curvature shape of any radii between 1/4" and 1 1/4".