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One feature common to all versions of the 9, 10 and 12-inch lathes was the huge number of thread pitches that could be generated - achieved by using a multi-slot changewheel arm that allowed an almost infinite variety of changewheel arrangements to be set up. Most threads between 4 and 96 t.p.i. could be obtained using just the standard changewheel set of: 2 x 20t, 24t, 32t, 36t, 40t, 44t, 46t, 48t, 52t, 54t, 56t and 3 x 64t (though the gear set supplied may well have varied over the years). When a screwcutting section was added to the handbook - strangely it was missing from the first edition of 1937 though space was provided for it to be added - the bulk of the publication consisted of charts showing how to arrange for screw threads and feeds and ways of setting up a vast number wire-winding options. All Atlas 9-inch, 10-inch and 12-inch lathe used changewheels of 16DP with a 14.5-degree pressure angle, a face width of 0.375", a bore of = 0.753 and a "double" keyway 0.1875" wide. The gears are interchangeable across the models to the extend that they fit on the same studs, but the one from the 9-inch have a thinner central boss.
Listed for only one year the Model D was also produced as a simplified version, the Model "E", as part of the Atlas "Unit Plan" system. Following the D came the long-lived power cross-feed Model F - which had not only a completely redesigned apron but a leadscrew increased in diameter from 5/8" to 3/4". Immediately before the introduction of the F the opportunity was taken to redesign and significantly improve the top slide assembly - the base casting of which had originally been in ZAMAK, a material unsuited to the strains of being fastened by two T bolts into a circular T slot cut into the top face of the cross slide (the front retaining bolt can be seen in the picture above). As the base casting was tightened down - and almost certainly exacerbated by taking heavy cuts - the casting distorted and caused the slide to bind. Atlas solved the problem by switching to cast iron and incorporating a stout post, cast integral with the cross slide over which the top slide dropped. Square-headed bolts, passing through the lower of the two top-slide castings, pushed short, bevelled-ended bars against an inverted conical face on the post and so drew it down tightly. After WW2 the English Raglan lathe employed an exact copy of this design - a feature that was to prove robust and entirely trouble-free. Strangely, one omission from the extensive Atlas accessory range was a full-length T-slotted cross slide, a fitting common for many years on most small British lathes and one that greatly enhances their versatility. If you would like a T-slotted cross slide for your Atlas lathes.co.uk sometimes have them available.
Illustrated at the bottom of this page the first 10-inch (10.25" x 24.5") Atlas lathe was introduced during 1934; the machine was considerably more robust than the two-year old Series-9 it replaced, especially in the area of the headstock where a completely redesigned casting resulted in a much stiffer structure. Bolted to the back of the headstock was a conventional backgear assembly and this, in conjunction with a two-step pulley drive from motor to countershaft, gave a very useful 16 speeds that spanned 28 to 2072 r.p.m. In general appearance the rest of the machine did not differ greatly from the original model and a further two years passed before the next revision, the Model D in 1936, addressed many of the machine's remaining weaknesses - this version being almost the final evolutionary form of the machine apart from the power cross feed Model 10-F introduced a year later and the quick-change screwcutting gearbox versions (QC42 and QC54 ) of 1947.
Enormously improved in almost every area the Model D lathe had long, stiffening bed feet, the saddle was given arms that tapered in thickness towards the outside edges, the compound slide redesigned on more robust lines and the compound slides fitted with zeroing micrometer dials. The headstock was further stiffened and the tailstock, strengthened and redesigned so as to "reach" further over the carriage, was provided with a "dip oiler" (often holding poisonous white lead) to lubricate the back centre. The changewheel cover, now in cast aluminium (or plastic when constructed in the UK) was held fast by a spring-loaded catch and some versions, especially those intended for use in educational and training establishments, were available with complete guarding of the drive belts. The swing of the lathe was 101/4" and between-centres' capacities of 18", 24" , 30" and 36" were all available. 16 spindle speeds were provided, from approximately 28 to 2072 rpm, depending on the motor used. The spindle was bored through 25/32", held a 3 Morse taper centre and was provided with a useful 60 hole, plunger-locked indexing device; the tailstock was No. 2 Morse. Because the backgear assembly was bolted to the back of the headstock this allowed the machine to be offered without the gears in simpler "utility" versions at a lower price.
Two designs of countershaft were offered, both with (screw-down) grease-cup lubricated Hyatt roller bearings held within simple but ingenious-designed self-aligning housings: the "Horizontal" bolted to the bench at the back of the lathe (and made the whole assembly rather deep front to back) whilst the "Vertical" was attached to the back of the bed and headstock and made a much more compact and portable unit. As offered in standard form the vertical type was not fitted with a belt-run guard (but individual guards were fitted to the backgears) whilst the horizontal type leant itself more readily to a simple guard that covered just the front run of the headstock belt. However, at considerable expense, an all-enveloping "safety" enclosure that appealed to schools and other training establishments was available for both the vertical and horizontal countershafts. Whilst the plain-bearing models are relatively easy to dismantle for a change of V-belt, the roller bearing models require the complete dismantling of the headstock. In the latter case (to save time and avoid damaging bearings) it is almost certainly better to use an industrial link belt of the T-link type.
Interestingly, the English versions, Sphere and Halifax and Acorntools, did not just sport different badges but had either the "maker's" name cast into the bed foot together with the claim "British Made" (Sphere) or with so few major mechanical differences (Halifax and Acorntools) that they must either have been specially constructed by Atlas, or copied and manufactured under licence in England or, more likely, built up there from a combination of made-in-England parts and original spares. It is certain that many standard Atlas lathes were imported into the UK by Acorntools (1930) Ltd. with war-time shipping manifests showing the supply of standard TV-36 models with individual serial numbers for each machine. The Halifax-badged version did incorporated several significant changes (although they are not evident on all examples): a screwcutting gearbox of the post-1958 type - but fitted to the earlier 10F-type lathe, tumble reverse (like the USA Craftsman model) instead of the leadscrew "reversing gearbox", plastic headstock and countershaft pulleys and a wider cross slide. The Sphere also had the wider cross slide and used plastic not only for the matching headstock and countershaft pulleys but also for the changewheel and headstock covers and even, on some models, for the leadscrew reversing gearbox casing and carriage-traverse handwheel; unlike the Atlas it had only one bolt holding down the tailstock end of the bed, rather on the lines of the Raglan Little John, with which it shares the clasp nuts and a few other minor apron parts - Raglan obviously saving themselves the cost of expensive new dies by adopting the readily-available and inexpensive American components. A variant of the Atlas offered by Acorntools during the 1940s and early 1950s, but not apparently market by Atlas in their home market, was a simple hand-operated capstan lathe. If any reader has an Acorntools, Sphere or Halifax lathe, the author would be pleased to hear from them.
Concurrent with the introduction in 1937 of the power cross feed Model F Atlas introduced a Timken taper-roller bearing headstock model alongside the plain-bearing type - the roller bearing set-up was described by the makers as being for: whenever the spindle speed must be exceptionally high for long intervals ..... for the shop handling both wood and metal work … The plain headstock, used a "babbit" or "white-metal" bearing, similar in arrangement to the plain bearings used on the crankshafts of I/C engines before the introduction of replaceable "shells". The plain-bearing headstock lathes, when properly set up, often give a better surface finish than the roller bearing models but, when worn, are very much more difficult and expensive to overhaul or replace. The bearings (on both 10 and 12-inch versions) had Timken numbers "engraved" on them that appear to have been (applied consistently over the years) as follows: Big Cone = 16150. Big Cup = 16284B. Small Cone = 14125A. Small Cup = 14276B. For a machine-tool application these would, originally, have been special high-quality units designated by the number "3" to indicate a close-tolerance fit - and also marked with either a dot or the letter "X" to indicate the high spot - so allowing the pair of bearings to be set with the marks in line to ensure the spindle ran as accurately as possible.
For a bench lathe the Atlas offered a truly vast turning capacity, whilst efficient American mass-production methods made the machine available at a very competitive price - and many thousands were sold worldwide. One small problem with the original version of the lathe is the little carriage-feed reversing gearbox at the headstock end of the leadscrew; this contains a mechanism involving ZAMAK bevel gears, all of which fall easy prey to heavy-handed operators. The box is designed to be used whilst the lathe is running, indeed, the makers claimed that as one of its beneficial features; however, if you wish it to have a long and happy life, press the operating lever firmly in the desired direction, but don't force it. It takes a moment or two for the engagement dogs on the face of the gears to match up and slide into mesh - and sometimes they baulk badly. The box also tends to develop play, and a careful setting-up session, involving shims, has been known to pay dividends.
Model numbers can be used to decode the original specification of a lathe: a "V" suffix indicated a vertical countershaft whist the letter "H" showed a horizontal drive system was used; if these letters were combined with a "T", as in TV-36, this showed taper rollers were used in the headstock. Digits after the letter(s) indicated the length of the bed, but not the capacity between centres; thus, "TV-48" would have been a vertical countershaft machine with taper roller bearings and a 48-inch long bed; the bed lengths of 36", 42", 48" and 54" gave between-centres capacities of: 18", 24", 30" and 36" respectively. After 1947 production costs were cut by simplifying the range: just two bed lengths (42" and 54") were offered, the option of the vertical countershaft was discontinued and (sensibly for this class of machine) roller bearings fitted as standard to the headstock. These lathes were coded TH-42 and TH-54 for changewheel screwcutting and QC-42 and QC-54 when fitted with a quick-change screwcutting gearbox.
In the USA large numbers of both the 10-inch 6-inch Atlas lathe were sold by Sear, Roebuck the famous mail-order store, and badged using their "Craftsman" name. Sears also sold other small metal-working lathes including the popular 109, and "Craftsman 80" (both made by the separate "AA Company") that are often confused with the entirely different (and greatly superior) Atlas 6-inch.
The Atlas Corporation published one of the very best instruction books ever commissioned by a lathe manufacturer, the Manual of Lathe Operation. This gives an exhaustive description of the machine's potential together with numerous screwcutting charts, clear instructions for common turning and other machining operations, diagrams, photographs and much useful general lathe-work advice. Copies are available.
Unfortunately non of the 10-inch lathes carried date stamps and production records are unavailable (though a retired employee is reported as giving a production number for the 10-inch lathe of over 500,000 units) and the only way of discovering when a machine was built is to examine the roller bearings in the headstock: each carries an engraved date marking (though front and rear bearings may be some months, or even a year or two apart) and will (if original and not changed, of course) give a good approximation as to when a machine was assembled..
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