Abstract: An improvement in a boring bar assembly is disclosed. The improvement relates to a lateral bar assembly in combination with the adjustable boring bar assembly of U.S. Pat. No. 2,838,316 issued to Albert Thomas, a co-inventor of the present invention. The improvement includes a lateral bar to which a major portion of the shank member of the boring bar assembly is removably fixed. The lateral bar has a plurality of longitudinally spaced threaded receptacles into which an end of the shank may be screwed. The shank may be selectively screwed into the lateral bar to thereby change the diameter of the boring bar assembly. The lateral bar may be varied in overall length with the number of receptacles likewise varied to thus vary the magnitude of the ranges of diameters of operation of the boring bar assembly.