Early Smart & Brown Model A Mk 1 4.5" x 18" (118 mm x 508 mm) circa 1947 - 1957
Like all the larger toolroom S & B lathes the speed-change gearbox of the model A was mounted inside the base of the cast-iron cabinet stand and the drive transmitted smoothly to the plain-bearing headstock by a flat belt. The apron contained an automatic oil pump whilst the headstock bearings, and gear drive to the screwcutting gearbox, were lubricated by a hand pump - the plunger handle of which can be seen protruding through the headstock cover.
The maximum collet capacity was 0.75" (19 mm), the spindle nose was 1.75" x 8 t.p.i and the headstock bore 63/64" (25 mm). The centres were No. 2 Morse taper, the twelve spindle speeds ranged from 39 to 1430 rpm. and the machine weighed 1736 lbs.
Pictures showing details of the Model A are lower down the page.
One important point about early versions of the Model A concerns the sometimes-encountered difficulty of changing speeds - this being done by a 3-position quadrant lever, on the front face of the stand, connected by a shaft to a three-speed gearbox mounted inside the cabinet. The design of this mechanism is faulty, the shaft connecting the lever to the gearbox being fixed rigidly in position on the lever, but free to move up and down with gearbox motor-support plate. As the latter is adjusted up and down to set the tension of the headstock drive belt, the shaft is deflected out of line making gear section difficult - or even impossible. The solution? Make sure that the belt is kept as short as possible; this means that any necessary adjustment of the belt's final tension is reduced to a minimum and hence shaft misalignment greatly reduced. As short-cut, if gear changing is difficult, before moving the quadrant lever, use the belt tensioning lever to slacken the belt, change the speed and then re-tension. Lathes.co.uk can supply the correct drive belt, made from either this or this.
Phone 01298-871633 for more details of belts and their fitting