An expandable downhole tool comprises a tubular body, at least one moveable arm disposed within the tubular body and being radially translatable between a retracted position and a wellbore engaging position, and at least one piston operable to mechanically support the at least one moveable arm in the wellbore engaging position when an opposing force is exerted. A method of reaming a formation to form an enlarged borehole in a wellbore comprising disposing an expandable reamer in a retracted position in the wellbore, expanding at least one movable arm of the expandable reamer radially outwardly into engagement with the formation, reaming the formation with the at least one moveable arm to form the enlarged borehole; and mechanically supporting the at least one moveable arm in the radially outward direction during reaming.
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims the benefit under 35 U.S.C. .sctn. 119 of U.S. provisional application Ser. No. 60/468,767 filed May 8, 2003 and entitled "Concentric Expandable Reamer", hereby incorporated herein by reference for all purposes.
