Believed to have been originally developed by Joseph Nason of New York, who obtained US Patent No. 10,383 on January 3, 1854 for an "arrangement for cutting screws in lathes." the "chase" system of screwcutting was widely used on precision bench lathes of all makes. The P & W was no exception and could be provided with an arrangement whereby a T slot, which ran down the back face of the bed, held supports that carried a sliding shaft holding a toolholder. Above this, at the headstock end, was a "master thread" driven by a selection of gears from the end of the main spindle in such a way that each "master" had its threading range extended by a multiple of six. A follower (with an insert carrying a few threads of the same pitch) pressed against the "master thread" and transmitted its form to the workpiece via a sliding shaft and threading tool held in an adjustable slide rest (illustrated left).
Whilst this system produced absolutely accurate threads - and was especially suited to delicate operations on thin-wall tubes used to construct such items as microscopes and telescopes - the length and pitch of thread that could be cut depended upon the availability of the appropriate "master".
Rather cleverly, each Pratt and Whitney "master" was supplied complete with a hob at one end for chasing a nut to suit the thread being generated by the lathe.
A very simple form of this screwcutting mechanism can be seen on the Goodell-Pratt Pages and other pictures of similar mechanisms on the Stark, Waltham Machine Works, Ames and Wade lathes.
Besides the system whereby the tool slide another form of chase screwcutting involved a sliding headstock spindle - a system that was to be even more highly developed when used on mass-production "Swiss Autos" used in the manufacture of tiny screws and other fittings for the horological and instrument trade. Makers of sliding-headstock spindle machines included most of the German makers of bench precision lathes including Boley, Lorch, Wolf-Jahn, Kärger and Auerbach.