US PATENT SUBCLASS 175 / 388
.~.~ Leading portion is a screw

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

327  DF  BIT OR BIT ELEMENT {21}
385  DF  .~ Bit with leading portion (e.g., pilot) forming smaller diameter initial bore {6}
388.~.~ Leading portion is a screw

DEFINITION

Classification: 175/388

(under subclass 385) Apparatus in which the leading or pilot portion describes a helical convolution, said convolution extending through at least 180 deg..

SEE OR SEARCH THIS CLASS, SUBCLASS:

394+, and the search there noted for other helical boring structure.