A tool for working a workpiece comprises an elongate member and a cam member. The elongate member comprises at least two extremities comprising at least one blade member. The at least two extremities are operable to separate in response to a pressurized medium. A conduit is in fluid communication with the extremities, and a pair of vents are in fluid communication with the conduit. The vents are operable to expel fluid communicated through the conduit. The cam member comprises an inner surface defining an opening. The inner surface of the cam resists expulsion of fluid from the vents, such that the cam and vents are operable to vary the pressure of fluid communicated through the conduit. The pressure variation varies the separation of the extremities as the elongate member is advanced through the cam toward a workpiece. The tool may be used to create bores having a non-cylindrical profile.