Smart & Brown Model M 4" x 18" This lathe was based closely on the pre-war German Boley L3/L4 with the 6 t.p.i. leadscrew disposed centrally under the bed and the whole of the changewheel bracket arranged to swing in order to provide a "tumble-reverse" to the leadscrew drive. However, the design was not left entirely alone, S & B deciding to fit a conventional full-width backgear assembly instead of the original type that was clustered up against the front spindle bearing - though they did retain the helical-form gears. On the Mk. 2 Smart & Brown further modified the lathe to include a neatly-engineered power shaft along the front of the bed to drive the sliding and surfacing feeds. On some versions of the Mk. 1 (including one owned by the writer) the cabinet stand was in cast aluminium, through most seem to have been in iron. The stand contained a motor, mounted on a simple adjustable plate fitted to slide rails that allowed the easy fitting of alternatives makes and sizes. A typical original fitting would have been a 3-phase, 3/4 h.p. Thomson-Houston 940 r.p.m. unit fitted with a 3-speed flat-belt pulley driving direct to the spindle. This gave nominal speeds of 411, 787 and 1432 r.p.m in open drive and through the 5 : 1 ratio backgear of approximately 82, 157 & 286 r.p.m. Some models are thought to have had a 3-speed gearbox in the cabinet base, in which case the number of speeds totalled 12, through with a very similar span from slowest to fastest.
For its size the lathe had a generously large spindle thread - 1 ¾" x 8 t.p.i. backed by a long (1 ¾" ) register length behind. The spindle was machined to take direct-fitting collets with a 25 mm diameter body - though if it were not for this arrangement the bore could easily have been made larger. Interestingly, the collets are almost identical to the Schaublin Type W25 - though the seat in the headstock spindle differs by a couple microns - probably a case of S & B putting the spindle bore on size whereas Schaublin put the collet on size and added 5 microns to the spindle bore.
Built in Mk 1 and Mk. 2 versions the first model appeared during late 1946 and the later - considerably modified - in 1948. Production ran, it is believed, until 1959. More details of the lathe's construction can be fond on the Boley page..