Expansible mandrel

Claim 1

FOR SUPPORTING A RING SUCH AS A CUTTER HAVING A FIRST BORE OF PREDETERMINED DIAMETER EXTENDING AXIALLY THERETHROUGH, THE COMBINATION OF, A FIRST TUBULAR MEMBER ROTATABLE ABOUT A PREDETERMINED AXIS AND HAVING A SECOND BORE OPENING OUTWARDLY AT ONE END OF THE MEMBER, MEANS DEFINING AN AXIALLY FACING SHOULDER AT SAID ONE END FOR ABUTTING AGAINST SAID RING, A THIN WALLED SLEEVE RIGID WITH AND PROJECTING FROM SAID ONE END AND ADAPTED TO TELESCOPE INTO SAID FIRST BORE, A SECOND TUBULAR MEMBER CONSTITUTING A RIGID EXTENSION OF SAID MEMBER AND TELESCOPED WITHIN SAID SLEEVE TO COOPERATE THEREWITH AND DEFINE A FIRST ANNULAR CHAMBER WITHIN SAID SLEEVE FOR HOLDING HYDRAULIC LIQUID, A SECOND CHAMBER FOR HYDRAULIC LIQUID DISPOSED WITHIN ONE OF SAID MEMBERS AND IN CONTINUOUS COMMUNICATION WITH SAID FIRST CHAMBER, A PISTON SLIDABLE IN SAID SECOND CHAMBER, AN ABUTMENT LARGER THAN SAID SLEEVE ENGAGEABLE WITH THE OUTER END FACE OF SAID RING WHEN THE LATTER IS TELESCOPED ON SAID SLEEVE, AND A SCREW AND NUT MECHANISM CONNECTING SAID ABUTMENT AND SAID PISTON INCLUDING AN ACTUATING ELEMENT MOVABLE RELATIVE TO SAID MEMBER IN ONE DIRECTION FIRST TO PRESS SAID ABUTMENT AGAINST SAID RING AND CLAMP THE LATTER AGAINST SAID SHOULDER AND THEN MOVE SAID PISTON IN A DIRECTION TO FORCE LIQUID FROM SAID SECOND CHAMBER INTO SAID FIRST CHAMBER AND THEREBY EXPAND SAID SLEEVE AGAINST THE WALL OF SAID FIRST BORE.