Of very heavy construction and considerable power, the three lathes in the SU"A" Series were first offered during the early 1960s, like many lathes by TOS, the machines took their model names from their swing over the bed, these being, in ascending order, 630, 800 and 900 mm. Although all shared an identical mechanical construction - the SU80A and SU90A being identical in all respects save for their centre height and spindle speed ranges - the SU63 was, in effect, a slightly scaled-down version. Its bed, at 567 mm wide, was appreciably narrow than the 698 mm of both the SU80A and SU90A and its spindle bore 60 mm against the 70 mm of the two larger machines.
Between-centres capacities varied from 1250 to 8000 mm on the SU63A and from 2000 to 8000 mm on the other.
All models had 30 spindle speeds, arranged in two groups of high and low by the use of a 12-speed gearbox, a 2-speed main drive motor and one pair of "pick-off" gears (gears that could be swapped from shaft to shaft to double or halve the ratio). The SU63 had a slow range of 8 to 375 r.p.m and a fast of 25 to 1180 r.p.m.; the SU80A had a slow range of 6.7 to 315 r.p.m. and a fast of 21.2 to 1000 r.p.m while the SU90A was set at suitably lover rates of 6 0 280 r.p.m and 19 to 900 r.p.m.
The standard motor supplied with the SU63A was a 710/1420 r.p.m unit of 18 kW (12 h.p.)  and that fitted to the two larger models one of 24 kW (16 h.p.) also running at 710/1420 r.p.m. The drive to the spindle passed through a hydraulically-operated, multi-plate clutch with two separate, powerful brakes also incorporated, one to stop the spindle and the other to operate on the bottom countershaft near the motor. Built into the spindle-speed change gearbox was a take-off to drive the lathe's power sliding and surfacing feeds, this also passing its drive through a multi-plate clutch.
40 rates of longitudinal carriage feed from 0.064 to 6.00 mm/rev and 40 in traverse from 0.025 to 0.2.32 mm/rev were available. Rapids, at the rate of 3000 mm/min and driven by a separate motor 1.1 kW 1420 r.p.m. built into the apron, were provided as standard - though only on the longitudinally feed .
Screwcutting, by a 60 mm diameter, 12 mm pitch leadscrew was arranged through two gearboxes, one big to provide a very wide range of Whitworth (inch), metric, module, diametrical and circular pitches and one small that housed supplementary gearing to cut normal metric threads with the aid of a rack-pinion system - a device also employed on some other models of TOS lathes. The system provided 36 metric pitches from 0.875 to 48; 42 English inch pitches from 96 to 7/8 t.p.i.; 36 module from 0.218 to 12, 36 Diametrical from DP 896 to 1.75 inches and 36 circular pitch 7/256 to 1.5 inches.
Equipped with a large No. 6 Morse taper, the tailstock spindle on all models was 120 mm with 275 mm of travel on the SU63A and 355 mm on the others
The shortest bed SU63A weighed 5 metric tons and the longest bed SU80A 10 metric tons. The full specification of the three lathes - and details of the various options and accessories can be found below..