Micro-adjusting cartridge for cutting tool

A boring tool with an adjustable cutting diameter, comprising a boring bar having a long axis and an outwardly facing, open recess extending along the long axis and a tool cartridge mounted in said recess, said cartridge having a bight portion with means for mounting the cartridge in said recess, a pair of legs extending from said bight portion in spaced apart, substantially parallel relation with each other and the long axis in said recess with an inner leg abutted against the boring bar and an outer leg carrying cutting means for cutting engagement with a workpiece and being resiliently movable relative to said inner leg, said legs each having transverse threaded bore means in axial alignment, with the threaded bore means of one leg having different pitch threads from the threaded bore means of the other leg, said cartridge further comprising transverse screw means threadably received in the threaded bore means connecting said legs and having an inner end terminating in said inner leg short of said boring bar so as to be out of contact therewith with the screw means having different pitch threads adjacent opposite ends corresponding with those of the respective threaded bore means such that rotation of said screw means moves said outer leg and cutting means thereon relative to said inner leg to adjust cutting diameter without said screw means having to engage the boring bar for such adjustment.