Introduced in 1952 as the SU50 Series of lathes - and steadily developed in the years following - in 1967 the revised SU50A range was introduced. Essentially the same mechanically, the new models were improved in several ways including a more modern appearance, higher spindle speeds driven by more powerful motors, and a wider range of screwcutting pitches and power feeds. A No.6 Morse taper was used in the tailstocks of the SU50A and SUK50A and a No.5 in the SS50A and SSK50A.
Intended as a general workshop and production lathe, the SU50A was the base version; designed for more rapid production work, the SS50A lacked screwcutting (as did similar "production lathes from other makers) but was equipped with both a powerful electromagnetic clutch/brake assembly and higher spindle speeds; fitted with a mechanism for repeated automatic work cycles, the SUK50A and SSK50A, both could also be used for ordinary, one-off jobs. 
All versions had the same 250 mm centre height and could be had with a choice of between-centres capacities of 1000, 1500 and 2000 mm. Full details of the various specifications can be found below..