Continued:
During the early 1940s, as industry switched over to war production, several variations on the standard lathe were produced including Craftsman-badged versions built to the better Atlas specification with two different types of roller-bearing headstock (instead of plain bearings); one was a standard Atlas unit with just a badge change and the other a specially-made headstock that resembled (with its frontal bulge) the shape of the ordinary Craftsman plain-bearing unit. For more details of the Craftsman versions, including departures from the official specification, click here.
Tumble reverse was fitted as standard to the changewheel drive, so allowing the spindle to run freely or to cut right and left-hand threads by just lifting or lowering a lever into spring-plunger indented positions. Because the lathe was capable of very high spindle speeds, the small-diameter tumble-reverse gears ran quickly enough to be unacceptably noisy; to cure this late-model machines (from some unspecified date) used plastic "gears to engage with the spindle - this fitting also having the benefit (as no shear-pin incorporated in the drive) of providing some degree of protection for the  relatively fragile ZAMAK gear train. Changewheels on all versions of the 6-inch were 24DP and with a 14.5-degree pressure angle.
A simple but adequate single-sided apron with proper twin clasp nuts and a "geared-down" drive from the handwheel to the leadscrew was used and remained unchanged for the life of the machine. Like that used on all other Atlas lathes the cross slide was of the "short" type that tended to wear the ways in their middle section, though it did carry a sheet metal cover at the rear to protect the feed screw.  No attempt was ever made to market, as an accessory, a T-slotted cross slide or boring table, both being useful and common fittings at the time on many British small lathes yet virtually never usedin America. The top slide could be rotated through 360º and, happily,  was T-slotted - so easing the fitment of alternative toolposts to the simple and traditional single holder fitted as standard. Unfortunately both the feed screw micrometer dials and handles were tiny though by way of compensation all the carriage hand controls, even the leadscrew clasp-nut handle, were chrome plated.  The leadscrew was threaded 0.5" Acme and a dial-thread indicator included in the standard equipment.
Although the headstock carried a No. 2 Morse-taper centre, the tailstock was only a No. 1 - possibly, together with the tiny feed-screw micrometer dials, the only real specification failings in an otherwise well-designed machine. A shorter-bed version, the "Model 612", with just 12 inches between centres, was also manufactured - but this seems to be a comparatively rare machine, despite the undeniable attraction of being light enough to be lifted by one person from under the stairs onto the workbench.
Although they are very different, confusion has arisen in the past between the Atlas/Craftsman 6-inch, and two other lathes sold be Sears (but made by the AA Company) the "109" and the later "Craftsman 80". The lathes produced by AA were very simple, minimalist machines and, in comparison with the Atlas, very inexpensive: in the mid 1950s an AA Craftsman 80 cost just $48 - compared to over $160 for the Atlas.
In view of the lathe's excellent specification, its compact dimensions and neat, built-on countershaft it remains surprising that, unlike its 10-inch brother, the lathe was not widely cloned overseas. One exception in post-WW2 years was the Swedish Högbo - a machine that copied the earlier rather than later countershaft design. On some versions of this lathe the bed was longer and given a V-way at the front and a flat at the rear - and other detailed changes incorporated as well.
In the early 1970s Atlas introduced a Mk. 2 version of the lathe; this was styled in a very "square" fashion and, with the traditional separate speed-reducing countershaft removed, had a very compact drive system with its eight speeds taken directly from the motor by a tensioned V-belt to a multi-step pulley mounted outboard of the left-hand end of the headstock spindle..

Atlas 6" lathe specially configured for armature reconditioning. A variety of specifications was available, all based on the use of a special set of Jacobs chucks, one of which contained a bearing to support to tail end of the armature, and the electrically-driven mica under-cutter head.

Roller-bearing headstock with flip-top oilers - adequate for this model, but not for the plain bearing of the "Craftsman" specification model which would have been safer with proper, continuous-drip oilers - or restricted to owners with a good memory and a conscientious character…..

Early bench-type countershaft unit used from the lathe's introduction until some point in 1940 when a modified version of the more robust stand-type was used instead.

The carriage assembly - with its 360 degree rotating top slide - remained unchanged during the machine's production life. Even though a T-slotted cross slide would have greatly expanded the lathe's versatility, and been a popular addition, Atlas never bothered to offer one.

Carriage drive gears, carried on a Zamak housing,  that gave a reduction between apron handwheel and bed-mounted rack.

A special intermediate bracket, Part No. M6-810, formed a hinge point for an adjustable motor-mount plate and acted as a carrier for the countershaft when lathes prior to M1975 were mounted on the maker's narrow, wooden-topped stand.

Stand countershaft unit with its mounting boss but less the motor platform.

Motor-Driven Mica Under-cutter.
This unit mounted in place of the cross slide and was used to cut back the mica insulation when a dynamo or starter armature had been cleaned up in the lathe.

Swivelling Vertical Milling Slide M6-500/500A with built-in vice - this unit plugged into the fitting normally occupied by the top slide and was a smaller version of that available for the 10" lathe.
Overall Height 111/2"
Vertical Feed 13/4"
Vise Capacity 2"
Jaw Depth 3/4"
Jaw Width 2"
Another picture here.

Bed-mounted micrometer stop

Bed extension 

A rare accessory: the genuine Atlas light unit with flexible stem and mounting bracket