Bone cutting apparatus

Claim 1

IN A TREPANNING APPARATUS OF A TYPE INCLUDING A BODY PORTION HAVING A LONGITUDINAL AXIS; DRIVE MEANS INCLUDING A ROTOR JOURNALED THEREIN AND HAVING AN OUTPUT SHAFT; MEANS FOR ROTATING SAID DRIVE MEANS AT SPEEDS IN EXCESS OF 20,000 R.P.M.; CHUCK MEANS ATTACHED TO SAID SHAFT; A CUTTER ELEMENT INSERTED AND RETAINED IN SAID CHUCK MEANS AND COMPRISING A SHANK PORTION AND A UNIFORMLY TAPERING BLADE PORTION, THERE BEING IN SAID BLADE PORTION A FLUTE HAVING A RAKE ANGLE SELECTED FROM THE RANGE OF FOUR DEGREES FORWARD TO TWO DEGREES BACKWARD; A STRUT FIXED TO SAID MAIN BODY AND LYING IN A PLANE CONTAINING SAID AXIS, WITH A GUIDE FOOT FIXED TO THE END OF SAID STRUT SO AS TO BE IN SPACED APART RELATION TO THE END OF SAID CUTTER ELEMENT; THAT IMPROVEMENT WHICH COMPRISES: SAID FLUTE FORMING A SINGLE CUTTING EDGE HAVING A RADIAL RELIEF SELECTED FROM A RANGE OF EIGHT THOUSANDTHS OF AN INCH TO SIXTEEN THOUSANDTHS OF AN INCH, WITH SAID CUTTER ELEMENT BEING DRIVEN AT SPEEDS IN EXCESS OF 20,000 R.P.M.; AND STRUT HAVING AN ISOSCELES TRAPEZOIDAL CROSS SECTIONAL FORM AND DISPOSED WITH THE LARGER PARALLEL SIDE PARALLEL TO AND SPACED FROM SAID CUTTING EDGE.