A Schaublin SV90, fitted with screwcutting, as offered during the mid 1930s
While the SV90 and SV102 looked superficially similar they were, in nearly every respect, entirely different and although each had an accessory range tailored to its exact requirements items could often be interchanged and also transferred from the smaller SV65 and SV70 models - though in the latter case the use of raiser blocks or other adaptors was often required. However, although the rest of the lathe might have been different, the standard SV90 and SV102 headstocks of early years were (apart from their centre height) identical - with an open, un-braced front and a 20 mm bore spindle, hardened and ground, running in adjustable bronze bearings. At the front the spindle bearing was formed with a long, shallow 3-degree taper and short 45-degree taper (in the manner first adopted in 1865 by Stark in the USA) with a plain parallel bearing at the other end. The cones of the 3-step pulley were 30 mm wide, with the largest carrying three rings of division holes (100, 60 and 48) in its flange and a single circle of 12 in its smallest. The bore of the largest collet that could be fitted was 14.5 mm. For the 102 model only the makers offered what they referred to as a "Reinforced" headstock; this had larger diameter bearings, wider (35 mm cone pulleys) and a 25 mm bore spindle that could accept collets with a maximum through bore of 17.5 mm. The W20-type collets (also used on the VM-102 screwcutting version) were 19.7 mm in diameter, 73 mm long with an unusual buttress-form thread of 0.780" x 1.666 mm pitch, a type also found on some Jones and Shipman grinding machines. Confusion can arise because not all collets marked W20 are identical - with some made to fit Mikron lathes, for example, being 19.75 mm in diameter, 80 mm long and with either a 2.0 mm or 1.25 mm pitch thread.
Two backgeared headstocks with a reduction ration of 1 : 5.15 were also available, both with a stiffening, half-height front wall: one, a standard-duty type with a 20 mm bore spindle fitted both the SV90 and SV102 whilst the other, a heavy-duty version for the 102 only had (like the "reinforced" version) larger diameter bearings, wider (35 mm cone pulleys) and the same 25 mm bore spindle that could accept collets with a maximum through bore of 17.5 mm.
Various drive systems were available from simple non-adjustable bench, wall and ceiling-mounted countershafts with fast-and-loose pulleys to more complex arrangements involving foot-operated pedals for engaging countershaft clutches to give instant changes of speed. The beautifully made bench countershafts units usually incorporated a socket into which a separate overhead drive system could be plugged - this long-used system providing a simple and reliable means of driving high-speed grinding and milling attachments held in the toolpost. In later years an effort was made to provide countershafts which were not only neater but also allowed the belt tension to be quickly and effectively adjusted with one particularly effective example, the Type 102.95.400, using a tall flange on the end of the electric motor to carry the drive shaft in an eccentric housing with the input and output pulleys arranged on each side of a large central bearing.
Copying the established American precision bench lathe makers Schaublin offered a huge range of accessories designed to convert a simple lathe into a multi-use machine-tool: in addition to previously-mentioned slide rests, production equipment and collets amongst the many items listed over the years were: vertical slides of early and later (stronger) types all with high-speed milling and grinding heads, swivelling T-slotted tables and vices - together with several different designs of the required "overhead" round-rope drive system; external and internal grinding spindles to fit in the toolpost; screwcutting attachments of four types: early sliding spindle, late sliding spindle; simple chase and chase combined with changewheels and "changewheel-direct-to-top-slide"; an attachment to provide power feed to the cross slide (this was combined with the screwcutting attachment); tailstocks with screw, lever and capstan-handle operation (the latter with and without a large micrometer dial), headstock, slide-rest and tailstock raiser blocks; headstock-mounted dividing units with indexing plates; adaptors to fit headstocks and tailstocks to the tables of Schaublin milling machines; several different kinds of single and multi (rotating) micrometer stop for the carriage and both cross and top slides; T-rests of various sizes for hand work; fixed steadies with closed and open bodies and a choice of bronze-tipped or roller fingers; faceplates with T-slots, tapped holes or a combination of both together with a selection of adjustable "finger" clamps to convert them for holding delicate parts; special "quill" holders to replace the tailstock that allowed high-accuracy spindles to be carried holding collets, faceplates and other fittings (the quills could also be fitted with pulleys and driven); saw tables and the necessary between-centres cutter arbors; a cam-turning attachment; roller filing rests with either single and double rollers; a number of different machine vices; a cross-slide mounted horizontal indexing and milling attachment; an unusual horizontally 4-way toolpost; an eccentric "chuck" (complete with adjustable counter-weight) that accepted both collets, faceplates and a conventional 3-jaw chuck (Schaublin's term for this unit was Universal offset and co-ordinate head); a centring microscope and stands with locking drawers, seats, footrests and electrical controls operated conventionally or by a knee hoop or foot pedals..
Tailstocks on early versions of the lathe can be something of a problem, being fitted with barrels having a 2° taper - hence not able to accept the more usual Morse fitting. The barrels are very hard and so extremely difficult to bore out - grinding usually being necessary to complete the job (it's usually far easier to make a complete new barrel in a more easily turned steel. The first versions, both pre and post WW", had a 25 mm diameter barrel, with the crudest of locking methods - a long slot in the casting closed down by a pinch bolts. This arrangement was fine when new but dangerous when worn, the extra force necessary to obtain a secure lock often being enough to snap the casting. By the 1950s the tailstock had been considerably strengthened (with a larger barrel and a proper split clamp to lock it) and by the 1960s improved further with the fitting of a No. 2 Morse taper socket - though unfortunately it was cheapened by the use of a plastic handwheel. For many years the tailstock incorporated a small reservoir and dipper rod, this originally being intended to hold white lead for application to the centre - and ideal substance for the task, but horribly poisonous. Final tailstocks were styled, like the rest of the lathe, in a more angular fashion , and finally, at some point during the 1980s, were provided with adjustment in two planes..