Abstract: A device for modifying a lathe having predetermined standard thread settings. Primarily, it can be used to adjust the lathe for extra non-standard thread cutting. The device is comprised of an adapter which can be attached to a compound tool rest for moving longitudinally the upper block of the compound tool rest a predetermined amount relative to the carriage during the thread cutting process. A calibrated scale can be set to add or subtract up to 10% from any lead selected from the standard thread series on the lathe. Automatic drive is provided by linking the motion of the carriage being driven by the worm screw on the lathe to the adapter. The adapter is comprised of a plurality of blocks which create a moment arm for moving the upper block relative to the lower block of the compound tool rest when the carriage is being driven.

Abstract: 1.