Upon longitudinal travel of template 1 at constant speed, tracer 2, equipped with a roller, raises valve spool 3. At this, fluid, delivered under pressure by pump 4 to valve body 8 at a pressure maintained by relief valve 5, is admitted to the upper end of cylinder 6 whose piston 7 is rigidly attached to an upright of the milling machine. Cylinder 6, as well as valve body 8 and milling cutter 10, is mounted on the vertical slide, and they travel upward until spool 3 blocks off ports in valve body 8, stopping fluid delivery to the upper end of cylinder 6. Fluid from the exhaust end of cylinder 6 is discharged through valve 8 to the tank. When tracer 2, held in contact with template 1 by spring 9, moves downward, a similar process is repeated, but only in the opposite direction. Thus, milling cutter 10 machines a surface on the work corresponding to the profile of template 1.
$4211$CHP,Dr$