Abstract: The device is designed for borehole reaming during casing—casing reamer shoes mounted in the conductor guide hole of a string or liner. The casing reamer shoe has a sub connected via a sleeve with a spiral mandrel having at least one screw groove, and a mandrel with a drill shoe located at one end thereof, and a pipe with at least one pin at the other end. The mandrel is mounted movably on the spiral mandrel inside a case being rigidly connected to the sub. The pin is arranged in the groove. The cross section of the screw groove has a shape of a trapezoid expanding in the direction of the longitudinal axis of the shoe. The pin has a stepped cylindrical shape with a conical transition. The device increases reliability and lifetime of the casing reamer shoe due to the shape of the grooves and pins.