(under subclass 327) Apparatus in which the cutter element or cutting edge of the bit is so arranged that the bit makes an annular cut in the formation and leaves a central undisturbed portion of the formation in the form of a cylinder.
(1) Note. Patents which specifically describe forming a core of the earth formation have been classified in this subclass even though the claims do not recite the forming of a core.
SEE OR SEARCH THIS CLASS, SUBCLASS:
4, for processes or devices in which a core receiver is driven into a formation by an explosive.
244+, and the search there noted for a core forming type bit combined with means movable relative thereto to receive, retain, or sever an undisturbed core.
332+, for a rolling cutter bit of the core forming type.
387, for a bit with a leading or pilot portion forming a smaller diameter initial bore in which the leading or pilot portion is core forming type. 402, for similar structure described for use as a casing shoe.
405.1, for a core forming type bit including diamond as a specific material.
421, for a forked rotary bit having structure which may permit the formation of a core.
SEE OR SEARCH CLASS
73, Measuring and Testing,
864.44+, for a sampling and tolling implement.
125, Stone Working,
20, for disk cutting saws for stone working.
408, Cutting by Use of Rotating Axially Moving Tool,
