1. IN A HYDRAULIC FEED PISTON-CYLINDER ASSEMBLY FOR CUTTING TOOLS AND THE LIKE, A SOURCE OF HYDRAULIC FLUID UNDER PRESSURE CONNECTED TO ONE END OF SAID ASSEMBLY, AN EXHAUST LINE LEADING TO A HYDRAULIC DRAIN CONNECTED TO THE OTHER END OF SAID ASSEMBLY, A FLOW REGULATOR IN SAID EXHAUST LINE OPERATIVE TO CONTROL THE FEED RATE FOR SAID ASSEMBLY, A FLUID CHAMBER CONNECTED TO SAID EXHAUST LINE AHEAD OF SAID FLOW REGULATOR, RECIPROCABLE PISTON MEANS PROJECTING INTO SAID FLUID CHAMBER OPERATIVE TO VARY THE VOLUME OF SAID CHAMBER TO MODIFY THE FEED RATE OF SAID ASSEMBLY, AND HYDRAULICALLY DRIVEN VALVE MEANS OPERATIVE TO RECIPROCATE SAID PISTON THUS TO MODIFY THE RELATIVELY UNIFORM FEED RATE OF SAID ASSEMBLY.