1. A TOOL MOUNTING ARRANGEMENT, PARTICULARLY FOR A PLANNING MACHINE WHICH CUTS ON BOTH FORWARD AND REVERSE STROKES, COMPRISING: A TOOL HOLDER; A TOOL HEAD MOVABLY MOUNTED IN THE TOOL HOLDER, SAID TOOL HEAD HAVING A CYLINDRICAL OPENING THEREIN; A TOOL HAVING A CYLINDRICAL STEEL SHANK AND ALSO HAVING A PAIR OF CUTTING TIPS AT ITS LOWER END, SAID SHANK EXTENDING UPWARDLY INTO SAID CYLINDRICAL OPENING IN SAID TOOL HEAD; CONICAL CLAMPING SPRING RINGS ARRANGED AROUND THE PERIPHERY OF THE TOOL SHANK AND DISPOSED WITHIN SAID CYLINDRICAL OPENING; AND A CLAMPING RING MOUNTED ON THE LOWER END OF SAID TOOL HEAD FOR MOVEMENT IN A DIRECTION AXIALLY OF SAID CYLINDRICAL OPENING, SAID CLAMPING RING BEING ENGAGEABLE WITH SAID CONICAL CLAMPING SPRING RINGS SO THAT AXIAL MOVEMENT OF SAID CLAMPING RING MOVES SAID CONICAL CLAMPING SPRING RINGS INTO OR OUT OF CLAMPING ENGAGEMENT WITH SAID TOOL HEAD AND SAID SHANK.