Stabilizer for drill strings

A rotary drill string stabilizer apparatus for use in rotary drilling of a bore hole:

• a body structure having connecting means adapted to secure such structure in a tubular running string, said body structure including a body member having a conical outer surface and a passage therethrough through which drilling fluid from the tubular running string can flow, a stabilizer comprising a stabilizer sleeve having a conical inner surface matching the conical configuration of said conical outer surface of said body member, said stabilizer sleeve being mounted on said body member with said conical outer and inner surfaces in friction contact, said stabilizer sleeve having an effective outside diameter conforming to the diameter of the bore hole, said sleeve having a plurality of longitudinal passages for the longitudinal flow of drilling fluid therethrough, longitudinally spaced peripheral seals preventing fluid leakage between said inner and outer surface from the region between said seals, and means for conducting fluid under pressure to the region between said conical inner surface and conical outer surface and between said seals to expand said sleeve and enable said sleeve to be moved relatively longitudinally along said conical outer surface to shrink-fit said sleeve on said body member upon relieving of the fluid pressure.