Abstract: A contouring and threading attachment for use with numerically controlled multi-function machine tools having automatic tool changing capability. The attachment has a spindle-actuated body adapted to detachably engage an adapter collar rigidly fixed to the outer end of the spindle sleeve. The body may be installed and removed by the automatic exchange arm mechanism of the machine tool and be stored in the tool magazine when not in use. A cutting tool on the outboard end of the attachment is movably radially of the spindle axis. The radial movements of the cutting tool are executed automatically through corresponding axial movements of the spindle under the numerical control of the machine tool.