One of  G.Boley's most popular and enduring models was the Series 3 and 4 - both very similar in construction but with the No. 3 lathe being of 90 mm (3.5") centre height and the No. 4  120 mm (4.7"). Illustrated below (with a photographic essay here of the later, more highly-developed models) these were enormously heavy, cleverly designed, beautifully made and elegant machine tools produced in a wide variety of models and with suffixes such as L, C, L, H, R, CR, BJ, HL, HM, etc. - the designation reflecting a precise specification and level of standard equipment. Production began in the early 1920s - as a plain-turning model with an open-drive headstocks and a variety of countershafts for bench or stand mounting drive - and extended to at least the mid 1970s by which time, in backgeared and screwcutting form, it was fitted to a very heavy cast-iron self-contained stand with built-in motor drive. While many 3L and 4L models were produced as plain-turning precision lathes, or set up with lever-action collet closers, capstan heads and cut-off slides for mass production work on small, close-tolerance components used in the watch, clock and instrument industries, large numbers were also manufactured, from the late 1920s, as backgeared and screwcutting models for use in toolrooms and repair shops. On the latter type the leadscrew ran in a fully-shielded housing beneath the bed whilst the twin "aprons" (they reached down both in front of and behind the saddle to form a particularly rigid housing) were joined together by a casting that supported the clasp nut in a perfect position directly beneath the centre line of the carriage and almost underneath the toolpost.
Neatly enclosed within the headstock casting directly behind the chuck  the backgear and its engagement system (when fitted) was a masterpiece of compact engineering, if a little awkward to engage on early versions--and a complete mystery if you don't know how. The secret lies in a small pressed-steel lever on the face of the headstock beneath the chuck (used to engage and disengage the gears) and a difficult-to-locate small screw marked (in very small lettering) "AUS" and "EIN" (in and out) on the side step of the middle pulley. If the screw is turned through 180 degrees, whilst simultaneous oscillating the pulley, a slight "clunk" will be heard as a small spring-loaded pin engages (or disengages) the pulley from the inner bronze backgear. With the pin out of engagement the pulley is free to turn on the spindle (together with its bronze gear) and so engage the backgear assembly to give slow speeds. The pushing force for the pulley-to-gear engagement pin was provided by a powerful spring, contained in a housing bored down through the depth of the largest diameter pulley. The tapping was capped by a large slotted screw that should be removed only if necessary (and be sure to contain the bits as the plug screw comes out). The saddle drive was fitted with an automatic, pre-set disengage to both left and right travel - a most useful facility when taking a long, fine-finishing cut. On some versions of this lathe the headstock pulley ran in its own bearings (concentric to the main spindle bearings) and drove the spindle though a peg - thus relieving the spindle of any loads from the driving belt.  The "tumble-reverse" was unusual in that the whole of the banjo arm carrying the changewheels was swung through an arc to pick up the respective drive gear. A knurled-finished handle below the left-hand headstock bearing operated the mechanism. The lathe was available in several other short-bed versions - the H, a simple repetition lathe, the PA for polishing, PS for finishing and the G for finishing and re-cutting threads. Several different stands were available, all of simple design with cast-iron legs and either wooden or metal tops. Models from the mid 1930s were offered with the option of a neat under-drive cast-iron stand with the flat-belt final drive coming from a V-belt countershaft unit built into the lower part of the headstock-end leg (illustrated below). The plain turning precision lathes used a very much simpler form of bed than the screwcutting models, although parts of the compound slide and tailstock - as well as a number of accessories - were common to all types and could be easily interchanged.
Although the G.Boley company no longer exists their machine tools remain in widespread use through industry, especially in repair shops. A typical example is the Swiss Rhaetische Bahn's locomotive shops at Landquart where a number of late-production, larger Boley machines, including a CNC affair, are in full-time use. Boley vices are everywhere in the spotless shop and, once a year they have a TdOT or open-house day (in case you are ever in the country at the time). RhB manufactures all the parts need to keep their narrow-gauge (1m) engines and rolling stock in perfect working order..
Some G.Boley models, both precision pain turning and screwcutting, were re-badged using the name "Swisten" for distribution in the UK.

Plain-turning Boley 3C (90 mm centre height) and 4C (120 mm centre height) with draw-tube collet closer and screw-feed compound slide rest. Theses were the simplest of the Boley 3 & 4 series and supplied for either bench mounting, or on choice of several different stands. Virtually all models of this type--and those shown below--continued in manufacture for many years with only minor changes in specification. One alteration incorporated when the lathes were to be mounted on underdrive stands was to guard the drive belt by bolting a cast-iron plate to the front face of the headstock.

Boley Model G tapping lathe. The two headstock pulleys were driven by belts running in opposite directions.  A dog clutch, set between the pulleys, was arranged to flick from one drive to the other, so reversing the tap at high speed. Many users used ingenious adaptations to this design including automatic operation of the clutch controlled by mercury switches.

Boley PA polishing lathe--though its actual use was for hand-turning or the finishing of small parts - the foot-operated collet closer allowing the operator to rack up a good bonus if he had taken tap-dancing lessons.