Illustrated below is an early example of the backgeared and screwcutting Portass Model S with its bed and headstock cast as one. Fitted with a 3-step headstock pulley, designed to be driven by a round leather rope, the lathe was fastened to a substantial cast-iron chip tray that was originally mounted on iron legs - the left-hand one of which carried a treadle-operated flywheel. The cut-out in the tray - in line with the headstock pulley - gave clearance for the drive belt. There was no compound slide - instead a single, swivelling tool slide could be fitted into either of the two T slots formed in the top surface of the saddle. The tool slide itself was T slotted - a useful feature for the model and experimental engineer.
Later models of the "S" had separate, bolt-on headstocks with the very last examples - which were generally of heavier build and better quality - having larger spindles and bearings as well.
Because no tumble reverse was fitted to the changewheel drive- and the extended saddle carried a full nut for the leadscrew - a simple but effective dog clutch was provided to allow for the instant disengagement of screwcutting and sliding feeds..