Abstract: An apparatus radially adjusts a position of a plurality of tool cartridges of a machine tool having rotatable, concentric, elongate, inner and outer drive spindles. A plurality of pockets are formed through the outer spindle to communication with a passage for the inner spindle. A wedge is disposed in each pocket for longitudinal movement in response to relative rotation of the inner spindle when the inner spindle is in a predetermined selectable position. A rotatable member is disposed in each pocket and has a threaded external surface operably engageable to move the rotatable member longitudinally in response to rotation of the rotatable member with respect to the outer spindle. A tool cartridge is operably engaged within each pocket for radial movement in response to relative movement of the corresponding wedge.