REAMING TOOL

摘要

This invention relates to a reaming tool for use in a subterranean well bore, the tool having axially spaced apart first and second reaming stages. 2-stage underreamers have been proposed in which the bodies of the upper and lower stages are releasably secured to each other by way of a threaded interconnection. Whilst such an arrangement considerably assists the manufacture of the tools it suffers from the disadvantage that very close manufacturing tolerances are necessary if, when the upper and lower body parts are screwed together, the blades on the upper and lower parts are to end up at exactly the correct angular position relative to each other. Further, the presence of a screwthreaded joint between the upper and lower stages of the tool reduces the strength of the body as compared with the strength of a unitary body.