US PATENT SUBCLASS 175 / 261
.~.~.~ With additional torque transmitting abutment on bit head and shaft


Current as of: June, 1999
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175 /   HD   BORING OR PENETRATING THE EARTH

257  DF  TOOL REMOVABLE OR INSERTABLE THROUGH OR AROUND DRIVING OR DRIVEN SHAFT OR CASING {2}
258  DF  .~ Laterally shiftable cutter element movable through shaft {2}
260  DF  .~.~ Cutter element engages torque transmitting abutment on shaft when expanded {1}
261.~.~.~ With additional torque transmitting abutment on bit head and shaft


DEFINITION

Classification: 175/261

(under subclass 260) Apparatus in which the cutter element is carried by a bit head and the shaft and bit head are also provided with mutually engaging drive transmitting surfaces which transmit torque between the shaft and bit head.