Patent ID: 7484571

Claim:
A downhole abrading tool for rotatably abrading an object in a well, the downhole abrading tool comprising: a body for connection to a drill string and having a drilling fluid passageway therethrough with an outlet for the passage of a drilling fluid having a drilling fluid pressure; a cutting end on the body for rotation against an object in the well; a chamber having a wear-away portion that is recessed within the cuffing end, the wear-away portion wearing away and exposing the chamber to a wellbore pressure when the cutting end wears a selected amount; and a movable restrictor in fluid communication with the chamber and the drilling fluid passageway and slidably carried within the drilling fluid passageway; for sliding movement along an inner wall surface of the drilling fluid passageway from a first position to a second position, the second position defined by a portion of the movable restrictor sliding along the inner wall surface of the drilling fluid passageway to at least partially block the outlet to create a pressure increase in the drilling fluid passageway when the chamber is exposed to the wellbore pressure.