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Atlas 6-inch Lathe Mk. 2
Additional Atlas 6-inch Mk.2 pictures here
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A Handbook and Parts List is available for this model

By 1974, after 37 years of production, the 6" Atlas (now catalogued as the Model 3950) had been extensively redesigned and, in an effort to keep the price competitive was being sold direct from the factory. Two versions were available, one Imperial (English) and the other metric; the latter machine, known officially as the Atlas 150, was able to cut only metric threads - of which 23 were available from 0.1 mm to 3.0 mm. The leadscrew, cross feed and top slide screws were also of metric pitch and the feed dials, tailstock barrel, threading chart were all in metric calibrations - in other words, a complete metric machine rather than just a simple screwcutting conversion.  The version with English calibrations offered threads between 8 and 96 tpi (or optionally, at extra cost, from 5 tpi) using, in addition to ordinary changewheels, a novel and ingenious system of "Gearsettes" - combinations of changewheels (sold in 6 different sets) marked with a circular metal disc that indicated the thread and feed range - together with an indication of which other gearwheels would mesh with them to provide the correct set up. As a comparison the Myford ML7 will only cut down to 8 tpi with the changewheel cover closed - if coarser threads are required the cover has to be left off and gears larger than 75t used on the exposed bracket.
A major change involved removing the expensive countershaft assembly, bolting the motor directly to the bench behind the lathe and fitting the headstock drive pulley in an overhung position on the left-hand end of the 17/32" bore, 1" x 10 tpi,  headstock spindle. To tension the belt, in the absence of any means of  moving the motor, a simple adjustable jockey pulley, sliding on a stud, was fitted above the belt run. Unfortunately this "modern" method of engineering a headstock drive had the effect of reducing the number of spindle speeds from 16 to 8 but with a still-respectable range of 55 to 2300 rpm with the maker's recommended 1/3 hp 1725 rpm 60 cycle motor. The Emco Compact 8, Myford 254 and various modern Chinese lathes also use a similar drive system - but were not the first small lathe makers to employ this cost-saving set up, the EXE Company of Exeter, England, used exactly the same idea on their machines in the 1930s, as did several makers of cheaper, less highly-stressed wood-turning lathes. The carriage showed evidence of cost cutting as well, though in this case the results were not so benign; the cross slide was still of the "short" type - which wore just the central portion of its ways - and an adjustable gib strip was fitted at the back of the saddle. This had become an old-fashioned method of adjusting the saddle to the bed in the 1920s and, although more complicated to engineer, the strip should have been placed at the front, so leaving a "solid" rear face to take tool thrust directly against the bed. Although, with its chrome-plated handles, the compound slide rest looked very handsome, lurking beneath the surface was a drawback: the gib strips were made of plastic and the metal-reinforced dimples for the adjuster screws tended to snap. This did not affect the side-to-side play by allowed the slide to lift when a heavy cut is made; making, or having made, a new set of metal gibs is the obvious, low-cost solution.
The tailstock could be adjusted to set over for taper turning, was solidly built and, happily, used a proper compression fitting to lock the 3/4" diameter spindle. The travel however was only 1.25 inches and the Morse taper a No. 1 - these (together with the very short cross slide) being the only serious specification failures in an otherwise well-designed little lathe sold at a price affordable by the amateur machinist.
In 1974 the lathe was painted grey but at some unknown point, before production ceased in 1980, this was changed to blue.
Mechanically the early and late versions of the Mk. 2 Atlas 6-inch are identical, however, early versions appear to have been fitted with Japanese-manufactured NTN ball bearings in the headstock whilst later models used Timken tapered-roller bearings. The lathe was 34" long, 17" deep and stood 11 inches high; it weighed approximately 92 lbs without its (extra-cost) electric motor. Additional Atlas 6-inch Mk. 2 pictures can be found here..

The outboard drive system as fitted to the late model Atlas 6" lathe. Instead of  engineering a system whereby the motor could be moved to release the belt tension (when a change of speed was required) a simple adjustable jockey pulley was fitted above the belt run.
Before the backgear assembly can be brought into operation the 4-step pulley must be released from the shaft by pulling out a small ring on its end.  See the detailed drawing below.

Engaging backgear on the Model 101 Atlas 6" lathe. At first sight there is no obvious way of releasing the large V pulley from its embrace with the spindle. The secret is the "external locking ring" on the end of the pulley; this is simply pulled outwards to uncouple it from the shaft and the backgear lever then operated as usual to mesh the respective gears.

The changewheels were arranged as "Gearsettes" - a system reminiscent of the Pick-O-Matic screwcutting used for a short time in the 1940s on the 10-inch lathe.

Three of the Gearsettes for screwcutting.

View from the back of the headstock showing the backer engagement lever and, on the right-hand face, the stud and nut used to tension on the main drive belt jockey pulley.

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