Originally 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 Sears, Roebuck Craftsman catalog until the late 1960s. Although rather crudely finished and detailed, its build was considerable more robust than early versions of the 109, 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, also sold branded as a Craftsman but with no connection at all to the AA lathe. The machine at the top of this page has been repainted grey - the one lower down is in its factory finish and, almost certainly, the very best of its type yet to be offered for sale.
While 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. For decades, most small lathes have been arranged so that carriage and tailstock run on different ways, or different parts of the same way, to ensure that the tailstock does not have to run over the bed worn away by the saddle and spoil its height alignment. Unfortunately, on all 109s, in the interests of economy, the ways were shared.
With a comprehensive threading chart attached to the front face, the headstock 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 equipped with a 1" x 10 t.p.i. nose and 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 stud 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 (a common failing on many Craftsman-branded lathes), 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 leadscrew was, for an AA lathe, of both unusually fine pitch and large diameter: 5/8" x 16 t.p.i.
A robust unit, the set-over tailstock was, after years of inadequate and frustrating use of the tiny No. 0 Morse taper, finally given the much more useful No. 1
Of all the AA109 versions this is the rarest, and hence probably sold only in limited numbers. .

The tumble reverse mechanism, carried on a crude bracket,  had to be unbolted before it could be moved and the carriage drive could be reversed in directions. Note the small adjuster screw, to set the mesh of the tumble gears with the headstock spindle gear, running through the casting from the top to impinge against the lock screw. Another adjuster ran through from underneath to set the mesh of the other gear.

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 rack and pinion gearing (instead of a handwheel on a leadscrew that ran though a full-nut on the apron), and both cross and top slides were fitted with micrometer dials.

Direct belt drive from the motor - the lack of an integral countershaft being a common failing on many Craftsman-branded lathes - was partially compensated for by the inclusion of an effective and neat epicyclic "backgear" built into the 3-step headstock pulley. It was engaged by preventing the rotation of the outer casing by a simple bolt, carried on a bracket bolted to the back of the bed. A small pin, visible on the front face of the pulley, would have required moving (though sideways or by extraction is not known) to allow the "planet" gears to be rotated by the "sun" gear attached to the 3-step pulley. Although the back of the headstock was completely open, as on previous 109 lathes, in this case the casting had not been further cut way over the top of the bearings but arranged to go as far back as possible to improve stiffness.