Abstract: There is disclosed a tool comprising a body having an opening which may be moved over a nut threaded onto a bolt and a surface on the opening to support the flat side of the nut, a bore in the body connected at one end with the opening opposite the supporting surface, and a rod having a cutting edge longitudinally reciprocal within the bore toward and away from the nut in the opening. The rod is so reciprocated by an operating system which includes a piston on the rod reciprocable within a cylinder on the body connecting with the other end of the bore.