Boring tool

In a boring tool having a shaft and at least one support which is inserted in a cylindrical blind hole in the shaft and is attached by means of a fixing screw, the support having a rear cylindrical portion with a circular cross-section adapted to fit in the blind hole and, adjoining this, a forward approximately half-cylindrical portion with an essentially semi-circular cross-section of the same diameter, the forward half-cylindrical portion having a recess for a replaceable cutting insert through which a clamping screw passes, the recess having a seating which is parallel to the top surface of the insert which passes approximately along a diameter of the shaft and abutment surfaces for the replaceable cutting insert, and in which a thread for the clamping screw is arranged perpendicularly to the seating, the improvement comprised in that the support has a second thread arranged parallel to the first thread for the clamping screw, the second thread receiving a fixing screw which is screwed from below through an oblong hole in the shaft into the support, wherein an adjusting screw is provided in the base of the blind hole and is arranged to be parallel to and displaced from the axis of the blind hole, the adjusting screw having a cylindrical centring shoulder which is a snug fit in a passage in the shaft and, adjoining the centring shoulder, a cylindrical spigot at its forward end, which is smaller in diameter than the centring shoulder and is a snug fit in a recess of the cylindrical portion of the support, and in which the rear and/or front end(s) of the adjusting screw have a depression to allow engagement of an adjusting tool.