Designed personally by Mr. Franklin Hardinge - and in production for the first time during WW1 (1914 -1918) - the fabulous Hardinge 9" x 28" "Cataract Quick-Change Swing Precision Lathe" was a new departure for the company. Built in very limited numbers - it is though that only three-hundred or so were sold - today 45 have been located with the serial numbers jumping from a 3-digit form at No. 334 to a 4-digit at 5789. The highest number so far found is 7374 with some evidence existing that production might have continued until as late as 1928. The earliest-known survivor is No.6 and the last example to emerge, No. 136, was found in England during 2017. As standard the lathe's capacity was, considering the enormous depth, width and weight of the bed, very modest but, as its name implied ("Quick-Change Swing"), it was possible to make better use of its strength  and order a set of raiser blocks for headstock, tailstock and toolpost that took the centre height from 4.5 to a more useful 7.5 inches. These blocks were missing from an example owned by the writer some years ago (date stamped 1917), a machine that had been standing  neglected for many years; although superficially in poor order, the quality shone through and with just a thorough clean, careful oiling and attention to the main adjustments it was successfully restored to active and accurate duty.
With an excellent general specification there were, amongst other delights, an enormously deep and wide bed, a carriage with immensely long wings and  a 21/32-inch diameter front headstock bearing carrying a massive, well-supported, hardened and ground 1.25" bore spindle that took 5C collets - a fitting that was to become rather popular. However, although the catalogue specification was for a 5C, it's entirely possible that lathes might have been supplied with alternatives - for example, a customer with a large collection of 4C collets might have ordered that fitting instead (the 4C has a body diameter of 0.95", a length of 3.00, not including the domed portion and a 15/8" x 10 t.p.i. thread; the 5C spindle thread is 23/16 x 10 t.p.i. 
Hardinge obviously went to an enormous amount of trouble with the design and patented not only the whole lathe (in so far as that could be done) but also each significant individual feature, including the quick-change screwcutting and feeds gearbox, the carriage and apron-feed mechanism, headstock bearings and ball bearing/thrust adjustment--and even the collet carousel (searching US Patents using the Google system will reveal most of the details). One useful fitting (continued until the present day on the Hardinge HLV-H lathe) was a quick withdrawal mechanism whereby the top slide could be instantly disengaged from a screwcutting job even with the spindle running at high speed. The original spoked, cast-iron backgears were perhaps on the fragile side - they have been known to strip - but this was the lathe's only known weak point. A full screwcutting gearbox was fitted and drove a 1-inch diameter 6 t.p.i leadscrew with a separate powershaft for the standard-fit power sliding and surfacing feeds (both engaged by safety-overload friction clutches) with an automatic, precision-adjustable disengagement to the sliding feed. Extremely long saddle wings overlapped the front and back of the headstock by several inches - giving improved support to the cutting tool when brought up to the spindle nose. Taper turning (with fine-screw adjustment of the setting) was fitted as standard; the top slide could be swivelled through 360° (just one square-headed bolt required slackening first); twin-bolts clamped the tailstock in place and a useful swing-out rotating collet tray was fitted beneath the chip tray. To improve productivity and the finish on work, the operator was encourage to use the right rate of feed (three being available for each setting of the gearbox) just a single control lever, which worked through the gearbox input gears, being used to make the change.
It appears that the Cataract Quick-Change Swing lathe inspired Mr. Edgar Holbrook to produce the very similar Model B No.9, a lathe with an identical bed, the same quick-withdrawal mechanism on the top slide and also, it is believed, a 5C collet fitting in the headstock spindle..