the rotating cutting tool of a sub - grader is adjustably mounted transverse the front of the frame of the machine upon a tool support in a manner which isolates changes in grade from changes in slope and which minimizes the influence of changes in slope upon the grade of the tool . the transverse pivot axis for grade control of the tool support is located at an intermediate point on the main frame , while the cutting tool , its associated drive means and housing are mounted on an independent pivot axis for slope control that extends longitudinally on one side of the main frame . any changes made in the grade are accomplished by raising and lowering the entire tool support on the transverse axis equally at both ends which does not alter the slope of the tool . the arc of movement is relatively long so that the change in fore and aft altitude of the tool is minimal . the rotating tool is maintained perpendicular to and in the plane of its longitudinal slope control axis by the tool frame . however , any changes in slope are entirely independent of the grade deviations and the tool is maintained in a desired plane at all times .