Made in Pavia, a city to the south of Milan in Italy, the Logos Swiss-type single-spindle auto lathe was a high-quality machine - though not as well known as similar machines from Index, Strohm, Gauthier and Thiel in Germany, Wickman, Herbert-BSA, Brown & Sharpe and EMI-MEC in England, Warner & Swasey in the USA and the instigators of the type, Petermann, Tornos, Bechler and Traub from Switzerland.
Over the years, Logos made a number of single-spindle automatic lathes including the models L13, L18, L24, LE30, LE36/42, LE46/52, LE52, L56/64 with the digits indicating the stock capacity through the headstock i.e. 13, 18, 24, 30, 36, 42, 46, 52, 56 and 64 mm respectively. In general, the lathes were fitted with from two six to four vertical turret-mounted tool slides and four horizontal slides, a double friction drive clutch, four instantly-changed speeds (two forward and two in reverse) and a downtime reducer. The types LE30, LE36/42 and LE46/52 had, in addition, electromagnetic control systems as standard. Full technical details and specifications can be found in the illustrations below,
If you've ever wondered how the thousands of millions of screws, other fasteners and assorted highly-accurate cylindrical parts are made so cheaply, the answer lies in lathes known as "Swiss-Autos" and single and multi-spindle automatic lathes.
The Swiss-Auto was originally an entirely mechanically-operated lathe that, alongside its close cousin the single-spindle automatic, was a machine tool designed specifically for the economical mass production of such parts. Until the advent of electronic circuits, a far greater range of manufactured items required such fittings, from use in watches, clocks, cameras and other optical devices to such items as parts for typewriters, mechanical calculators and a vast range of cars, aircraft and marine and scientific instruments. The originators of this specialised lathe were based in Switzerland, in the large village of Moutier where, from the early years of the 20th century, three competing Companies, Tornos, Bechler and Petermann existed side-by-side. However, beginning in the late 1960s, a series of takeovers and mergers resulted in one surviving Company, Tornos S.A. having absorbed the others. The men responsible for pioneering developments in the field were Joseph Petermann, André Bechler and, the owner of Tornos, Willy Megel - their lathes all incorporated three essential design features: a headstock (or headstock spindle) able to slide backwards and forwards; a series of precisely-adjustable toolholders arranged above or around the spindle nose in a fan shape and operation of the various feed and other movements by specially formed cams.
Even today, during the early decades of the 21st century, such basic, mechanically operated lathes still find employment where a simple, low-cost yet high-precision solution to manufacturing needs is required (the writer receiving numerous enquiries from countries such as India). Though complex mechanisms in their own right, the Swiss-Auto's ease of operation and running adjustments, compact dimensions and reliability over very long production runs are still hard to beat - though making the cams and setting up the numerous adjustments does take some mathematical knowledge, skill and experience.
The writer has personal experience with such a machine that, decades old when installed in a friend's sound-proofed domestic garage and fitted with an automatic bar feed unit, could be left running non-stop for days and nights filling hoppers with profitable little items.
Now adapted to computer control, both the Swiss Auto and single-spindle automatic are unsurprisingly, still being built by numerous makers worldwide (Japan having had considerable success in the field) - a term often used for this trade is the "Bar-turning Industry".
All original, mechanical-type Swiss-Autos were arranged along similar lines with, depending upon the model, up to six independent tool holders arranged radially on a cutter frame fixed in front of the (right-hand positioned) headstock nose. Each tool-holder was arranged to slide, its action triggered by a rocker arm connected (via a series of linkages) to a rotating cam. For round components only finely ground bar stock could be used, the job being either very short and so requiring no outboard support, or long enough to pass through one of several kinds of bushed steady that held the work both accurately and securely against deflection. The longitudinal feed was obtained by sliding the whole headstock along the bed, at various rates and timings, also under cam control. By combining headstock and tool movements, cam shapes, cam timing and with various types of cutting and forming tools (and by mounting accessories) the lathes could perform miracles of miniature production engineering. When producing tiny parts, an important point was the very precise adjustment of the cutting-tool holders - and in this the "setter" was, originally, the highly-paid king of the shop floor. In the early day the best results could only be obtained by long experience and trial-and-error-methods but, with the introduction of Petermann's "micro-differential" apparatus, where a micrometer was mounted on the end of each toolholder, the task became greatly simplified. The first setting took accuracy to within 0.01 mm of turned diameter and the second to within 0.001 mm (0.00004"). As one setter of these machines remarked: ….there is a sense of achievement and excitement when all the tools and cams are fitted and the machine timed up; and then, after a short session of adjustment, to go on and manufacture thousands of identical parts, all new and shiny..