TOOL FOR EXPANSION OF SHAFT OF HOLE Russian patent published in 2001 - IPC

FIELD: mining industry. SUBSTANCE: proposed tool is made of milling cutter linked to shaft of hydraulic face motor whose frame is coupled to lower end of rod of piston mechanism whose body in its turn is joined to lower pipe of drill pipe string. Piston coupled to rod and stopper are housed in body of piston mechanism. Rod is smoothly bent in axial direction. Milling cutter is manufactured in the form of rolling cutter bit which outer surface has shape of ellipsoid and its symmetry axis is displaced in parallel with regard to axis of linking thread of body of milling cutter. EFFECT: enhanced functional efficiency of tool. 2 cl, 4 dwg