Abstract: A threading attachment is provided in the tooling area of a multiple spindle machine tool, wherein the tap holder is rotated by a motor which has an infinitely variable speed within a given range and includes a first speed for advance movements to tap workpieces. This advance movement is provided by a motive power unit to move the tap holder in the advance movement and also in a retract movement at the completion of tapping. The motor has a second variable speed condition to back the tap out of the workpiece. This threading attachment is modular in construction to permit it to be physically mounted in any of the spindle positions of the multiple spindle machine tool and to be capable of being utilized with machine tools of different frame sizes. The foregoing abstract is merely a resume of one general application, is not a complete discussion of all principles of operation or applications, and is not to be construed as a limitation on the scope of the claimed subject matter.