Retrievable drilling apparatus

Claim 1

IN A RETRIEVABLE DRILLING BIT ADAPTED TO BE LOWERED WITHIN AND COUPLED TO THE LOWER PORTION OF A STRING OF PIPE DISPOSED IN A WELL BORE: A UNITARY BODY MOVABLE LONGITUDINALLY THROUGH THE PIPE; A PLURALITY OF INITIALLY RETRACTED CUTTER MEANS MOUNTED ON AND CIRCUMFERENTIALLY SPACED ABOUT SAID BODY FOR EXPANSION LATERALLY OUTWARDLY OF SAID BODY; SAID BIT INCLUDING MEANS ADAPTED TO ENGAGE A LOWER PORTION OF THE PIPE TO LOCATE THE BIT IN THE PIPE WITH SAID CUTTER MEANS PROJECTING BELOW THE LOWER END OF THE PIPE; MEANS CARRIED BY SAID BODY FOR EXPANDING SAID CUTTER MEANS FROM ITS INITIALLY RETRACTED POSITION LATERALLY OUTWARDLY OF THE BODY TO DRILL AN EFFECTIVE HOLE DIAMETER GREATER THAN THE OUTSIDE DIAMETER OF THE PIPE; AND MEANS FOR COUPLING SAID EXPANDING MEANS TO THE PIPE, WHEREBY THE PIPE IS ADAPTED TO ROTATE THE BIT AND TRANSMIT TORQUE THROUGH SAID EXPANDING MEANS AND BODY TO SAID CUTTER MEANS.