Patent ID: 7188689

Claim:
A variable gauge drilling apparatus comprising: (a) an apparatus housing having a housing size which is suitable for insertion in a subject borehole which has a subject borehole size within a design range of borehole sizes; (b) a plurality of interchangeable borehole engaging devices having different device sizes for mounting on the apparatus housing to provide the drilling apparatus with a drilling apparatus size within a range of drilling apparatus sizes, wherein the range of drilling apparatus sizes is compatible for use of the drilling apparatus within the design range of borehole sizes, wherein the plurality of interchangeable borehole engaging devices is comprised of a plurality of interchangeable rotation restraining devices; and (c) a universal borehole engaging device mount located on the apparatus housing, wherein the mount is configured to accept for mounting any one of the plurality of interchangeable borehole engaging devices, wherein the mount is comprised of a pocket defined by an exterior surface of the apparatus housing; wherein each of the plurality of interchangeable rotation restraining devices is comprised of a rotation restraining assembly for mounting in the pocket, wherein the rotation restraining assembly is comprised of an assembly housing and a rotation restraining member connected with the assembly housing, wherein the assembly housing has an assembly housing size and wherein the assembly housing size defines the device size.