Finished in gold paint the 3-inch centre height by 19.25" between centres Model 109.21280 was the last lathe made by the AA company and listed in the Craftsman catalog until the late 1960s. Although rather crudely finished and detailed its build was considerable more robust than early versions with a distinctly "square" appearance to the headstock - the styling of which has sometimes caused it to be confused with the later Atlas Mk. 2 6-inch - which was also sold branded as a Craftsman.
Whilst previous 109 beds had been formed with two V-ways on this last model the front was a V and the rear a flat - with both shared by carriage and tailstock. Most small lathes have been arranged for the carriage and tailstock to run on different ways, or parts of the same way, to ensure that the tailstock did not have to run over the bed worn away by the saddle and so spoil its height alignment. Unfortunately, on all 109s, the ways were shared.
The headstock, with a comprehensive threading chart attached to the front face, had its back section left completely open (in traditional 109 style) but was not, as on previous models, further cut way over the top of the bearings; instead, to improve stiffness, the side walls were made as deep as possible from front to back. The spindle, much heavier than on any previous AA lathe and quipped with a No. 2 Morse taper socket, ran in plain bearing and was fitted with a 5 : 1 ratio epicyclic slow-speed "backgear" built into the largest diameter of the 3-step pulley. In order to engage the low-speed range the outer casing of the epicyclic gear was prevented from rotating by a crude bolt carried on a bracket bolted to the back of the bed. Once the casing was immobilised, and a small pin removed to allow the internal "planet" gears to be rotated by the "sun" gear attached to the drive pulley, the mechanism would turn and provide a range of low speeds. Even though the headstock pulley was driven directly from the motor, with no intermediate speed-reducing countershaft, the arrangement gave a total of 6 speeds of which the slowest just allowed for safe screwcutting and the turning of large diameters on a faceplate.
Although constructed as previous 109 models with apron and saddle cast as one unit the entire carriage assembly was completely re-engineered. The full-depth apron carried a proper handwheel, driving through a reduction gear to a rack on the bed (instead of a handwheel on a leadscrew that ran though a full-nut on the apron), and both cross and top slides (the latter looking remarkably similar to that used on the contemporary 6-inch Atlas) were fitted with micrometer dials.
Unlike earlier models of the 109 the tumble-reverse lever, which allowed the carriage travel to be reversed and right and left-hand threads cut at will, was not located by a spring indent; instead the end cover had to be opened and the unit unbolted before the gears could be repositioned. Small adjuster screws, to set the mesh of the tumble gears with the headstock spindle gear, passed through each side of the casting to impinge against the locking bolt.
The set-over tailstock was a robust unit and, at last, after years of inadequate and frustrating use of the tiny No. 1 Morse taper, was given the much more useful No. 1
Of all the 109 versions this is the rarest, and hence probably sold only in limited numbers..