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Bed and Stand
220mm wide and of massive depth the hardened rectangular-way (flat-topped) bed was braced by enormous cross webs and immensely rigid. It was further strengthened by being mounted on a stand of typical Schaublin design and construction with a one-piece cast-iron base topped by an integral (but rather-too-small) chip tray. The right-hand section of the cabinet held the electrical switchgear, the left hand compartment the drive system with the back face cut away to house a neat, tall, 22-litre coolant tank and motor-driven pump.
Compact and self-contained the drive system was housed around a large aluminium casting, with a 2-speed 0.9/3.0 kW 750/1500 r.p.m. motor in the base driving upwards by a variable-speed system that used a wide, V-edged belt running over expanding and contracting pulleys to an Ortlinghaus combined oil-immersed, multi-plate, spindle-mounted clutch/brake unit. The final drive to the headstock spindle was positive, by toothed belt. The motor was switched on and off by a lever connected to a control shaft that ran the length of the bed whilst turning a large, full-circle wheel on the left-hand face of the cabinet opened and closed the pulleys and varied the spindle speeds. Selection of low and high-speed ranges was by means of a lever mounted concentrically on the speed-change handle shaft whilst a long pedal, positioned along the stand's lower front edge, applied and released a powerful spindle brake that allowed the motor to continue running whilst the spindle was braked to, and held safely at, a halt. To release the spindle so that it could be turned by hand (to inspect a job or release a chuck) a separate shorter pedal to the right of the brake was pressed.
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Continued:
Headstock and fittings
Using a strong, internally-ribbed rectangular casting the headstock was adjustable on the bed for alignment and carried a 28 mm bore, D1-3" camlock spindle running in two pairs of pre-loaded, ultra-precision angular-contact ball bearings grease packed for life. The choice of these very expensive bearings was to ensure that accuracy would be maintained over an unusually long service life.
Collets played an important part in the expected use of the 125 and the inside of the spindle nose was adapted to take direct-mounting, draw-bar retained, Schaublin-manufactured Type B32 with a maximum through capacity of 24mm - whilst for the special internal-gripping stepped collets (capacity 20 to 120mm capacity) and external-gripping stepped collets a special D1-3" nose-piece adaptor was available. An expensive, high-accuracy collet set designated B32-UP (ultra precision) was also listed and had a guaranteed accuracy of concentricity of 0.005mm - or better. For these collets a special quick-closing drawbar (part 125-21.255) was required. A range of D1-3" mounts to hold hardened-steel expanding arbors was also offered and (to special-order only), conversions to accept standard Schaublin W20 and W25 external and internal-gripping stepped collets, closers and expanding arbors. Besides the ordinary hand-operated lever type, for rapid production work the makers made available several designs of collet quick-closer including pneumatic and hydraulically operated types. Even the faceplate and drive dogs supplied as standard were high-quality, specialised items - the former being not only very heavy (at 7.7 kg) but also equipped with 4 T-slots and thirty M8 tapped holes - whilst the 8 dogs, with a maximum bore of 30mm, were in hardened steel.
With the drive system and speed changes concentrated in the stand all the headstock-mounted controls were concerned with screwcutting. The position of the controls makes a useful short cut to working out the exact Model of 125 - especially when viewing photographs of a potential purchase where the vendor may be unaware of the important differences between the versions (and their widely differing values). On the Model A the front face of the headstock was bare; the B had one knob at the top and a dial beneath and the C two knobs at the top, a dial and lever below and a dial on the inner face below and in front of the spindle. In the case of the Model C, the upper left-hand knob selected four ranges of English pitches, the upper right swapped between English and metric threads whilst the lower and front-face dials set individual pitches. The small lever in the lower right hand corner reversed the direction of the leadscrew to give right or left-hand threads.
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Continued:
Carriage and power feeds
At the tailstock end of the bed was what Schaublin termed the "turning gearbox" - an assembly of gears driven by a 0.24 kW variable-speed DC motor working though an adjustable, multi-plate safety clutch that gave longitudinal and traverse feed rates from 4 to 260 mm per minute. However, the drive was not as straightforward as one might have expected and, instead of a separate power-shaft working through worm-and-wheel gearing (to preserve the leadscrew just for screwcutting) Schaublin, reflecting practice as employed for many years on the popular 102-VM made the leadscrew perform both tasks. However, this was no ordinary leadscrew but exceptionally large (40 mm diameter and 4 mm pitch), hardened and ground, running in angular-contact bearings and clasped by long nuts provided with positive oiling. To provide power cross feed a shaft emerged from the rear of the "turning gearbox" passed down the back of the bed to drive the cross slide through bevel gears. This rear-drive system, used countless times before, by numerous makers from the late 1800 onwards, had the merit of allowing both simplified apron gearing and operating controls. A single lever, on the inside face of the turning gearbox, selected the feed direction (along or across the bed) with an electrical switch for forward or reverse/in or out together with a dial to vary the speed of cut.
Simple, easily operated and well thought-out the apron-mounted controls even extended to the provision of good-sized levers to lock the carriage and cross slide. Running through the apron was a long control rod (as used on the 102-VM) that allowed the power sliding feed to be knocked off in either direction and (by the use of retractable dogs) both the feed and spindle to be stopped when screwcutting - the latter a true boon to the busy machinist and a wonderful safety feature. As a further refinement high-speed screwcutting was possible where, on completion of a cut, moving a lever instantly retracted the cross slide; shifting the lever in the opposite direction caused the carriage to automatically return to its starting point allowing the operator to apply more cut and start the process again. As the makers claimed, with this system in operation it was possible for: "… even operators without any particular skill to rapidly succeed in producing quality threads in several passes without any risk of mistakes." The base of the double-wall apron held a supply of oil, distributed around the inside and to the bed, cross slides ways and leadscrew clasp nut, by a hand-operated plunger pump that the makers recommended be operated every 2 hours. Also provided (though unaccountably on the tailstock side of the carriage), was a rotating 6-position stop. The compound slide assembly was a model of smoothness and accuracy with the 130 mm travel cross slide carrying ruler marking along its front edge, dovetailed edges (as on many Colchester lathes of the time to allow the quick and accurate mounting of a rear toolpost) and an adjustable 2-position stop. The 90 mm travel top slide sat on a wide, circular base (with a particularly strong clamp), and both feed screws were hardened, ran through bronze bushes and were equipped with beautifully engraved (0.01 mm interval) dials - with that on the cross slide positively locked by a through bolt, a method that eliminated any chance of slippage. Both feed screws were of the same pitch with one turn of the handwheel giving 2 mm of travel.
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Continued:
Screwcutting
Incorporated in the Type B screwcutting arrangements was a permanently mounted 127t gear that allowed both English and metric threads to be instantly available by simply moving a selector on the face of the headstock. The arrangement did not obviate the necessity to rearrange the changewheels but, with such a large number provided as standard (21t, 23t, 24t, 28t, 36t, 42t, 48t, 56t, 2 x 60t, 72t, 80t, 84t 88 and 90t) all metric pitches between 0.25 and 8.00 mm could be generated, as could all English between 112 to 3 threads per inch. The proper screwcutting gearbox fitted to the Model C was also fitted with the 127t gear that allowed metric and English threads to be cut without having to disturb the gear train and gave 24 metric pitches including 19 marked ones of: 0.25, 0.35, 0.40. 0.50, 0.70, 0.75, 0.80, 1.00, 1.25, 1.40, 1.50, 1.60, 1.75, 2.00, 2.50, 2.80, 3.00, 3.20 and 3.50 mm and 72 English pitches including 32 marked of: 112, 88, 80, 77, 72, 70, 64, 56, 48, 45, 44, 40, 36, 35, 32, 28, 24, 22.5, 22, 20, 18, 17.5, 16, 14, 12, 11.75, 11, 10, 9, 8.75, 8 and 6 threads per inch. Extra changewheels were also available - 42t, 46t, 2 x 48t, 55t, 56t, 60t, 65t, 72t, 79t, 80t and 84t - that permitted virtually any pitch to be generated between 0.25 and 8.00 mm and all "special" English pitches from 112 to 3 t.p.i.
Tailstock
An early version of the tailstock was of rather lighter construction than the later - but both had a No. 2 Morse taper, 100 mm of spindle travel with self-eject and a knockout tang slot, provision for correcting any error in lateral adjustment (though the unit did not set over for taper turning) and wipers on the bed guide ways. The handwheel was equipped with a micrometer dial reading to 0.1 mm and a circular (Perspex covered) inspection window provided halfway along the casting to read the 1 mm division ruler scale. Also available was an alternative tailstock with capstan-handle operation to a larger No. 3 Morse taper spindle through a rack-and-pinion drive. However, it was not possible to fit this feed mechanism to the standard tailstock, an entirely different casting being required.
Schaublin offered a wide range of accessories for the 125, some specially built, others adapted or borrowed from other lathes in their range. Items varied from hydraulic copy attachments to centring microscopes and high-speed grinding and milling attachments driven from a self-powered "overhead". 
All versions of the Schaublin 125 weighed nearly 1000 kg (1 ton), were 59-inches (1480 mm) long, 29-inches (730 mm) deep and 50-inches (1280 mm) high..
Tony Griffiths

Compact and self-contained the drive system was housed around a large aluminium casting, with a 2-speed 0.9/3.0 kW 750/1500 r.p.m. motor in the base driving upwards by variable-speed system that used a wide, V-edged belt running over expanding and contracting pulleys to a combined oil-immersed multi-plate spindle clutch/brake unit. The final drive to the headstock spindle was positive, by toothed belt.

Schaublin offered a wide range of accessories for the 125, some specially built, others adapted or borrowed from other lathes in their range. Items varies from hydraulic copy attachments to centring microscopes and high-speed grinding and milling attachments driven from a self-powered "overhead". 

Centring Microscope part: 70-89-500. 50X magnification with eyepiece angled at 90 degrees, reticule with cross hairs and 12 concentric rings. Also shown in the picture are, to the left, the lighting unit (part 70-89.510) and to the right the 220/3.5-v transformer (Part: 70-89.510)

Part 102-76.200 Centring and Measuring Microscope on a No. 2 Morse taper for use in the tailstock or other applications. 60X magnification, 20 mm measuring capacity and an accuracy of 0.01 mm. This version was supplied complete with a built-in lighting unit, 220/3.5-v transformer, flex with miniature plug, 4 spare bulbs and a protective case.

125-21.800 Dividing Attachment for mounting on the headstock to index the spindle. The 3 plates each had 6 rings of holes. This unit allowed all standard divisions between 2 and 360 and was supplied complete with special rear headstock cover.

The Dividing Attachment in place on the headstock and in use with the Overhead Attachment (102-95.100), Vertical slide (125.87.300) and high-speed Milling and Grinding head.

Left: the Overhead Attachment with 3-phase, 1500 r.p.m. 0.25 kW motor (76.800) and switch (71.206).

Complete Vertical Milling Attachment (listed as 125-87.350) comprising the Column Unit (125-87.300) and swivelling "headstock" (102-87.450) with high-precision ball-bearing quill to take W20 collets. A wide range of extras was available for this unit including: a pawl-operated dividing head, geared reduction unit, swivelling vice and T-slotted angle table, high-speed grinding and milling attachments and various collet holders. All milling accessories carried the part number  "87".

Speed Reduction unit (102-87.380) with a 5 : 1 reduction. Fitted in an oil-tight housing the spindle and gears ran on ball bearings. Speed range 220 to 1080 r.p.m.

The Lever-operated Collet Closer was made as a detachable unit under part 125-21.60 and accepted collets of the B32 type or, with the special "Ultra Precision" B32-UP type collets with a special drawbar 125.20-255. Both pneumatic (125-21.500) and hydraulic (125-20.185) closers were also manufactured.

Capstan-handle Tailstock with large diameter micrometer dial and a No. 3 Morse taper spindle instead of the No. 2 of the standard tailstock. Designed for production work a 4-station rotating capstan head  to fit into the Morse taper was also available (Schaublin "oblique turret" part no. 125-67.000).

Automatic Tailstock Spindle-feed Attachment (125-66.490) for the capstan-handle tailstock. The unit consisted of a spring-loaded piston to attach to the spindle and a collar that engaged with the carriage (by which means the feed was made). The unit also required the use of  the T-slotted rear supporting block 125-46.095

Raising Block 125-5.010 with the bed profile of the 102 lathe. With many companies and individuals having Model 102 lathes as well this allowed them to adapt parts from one to the other

Spherical-turning Attachment 125-53.000 for convex or concave turning. The toolpath was controlled by a handwheel working through worm-and-wheel gearing with 2 adjustable dogs to limit the angular rotation. The maximum diameter that could be turned was 120 mm and a vernier was fitted that allowed an accuracy of cut down to 0.01 mm. Besides toolholders (125-53.050 for convex turning and 125-53-055 for concave) the unit was supplied with a reference square carrying and adjustable centre for centring and measuring the work radius.

T-slotted, drilled and tapped faceplate 125-20.110

Hydraulic Copy Attachment 125-53.850 by Duplomatic - Model TB-80. This unit had a radial copying stroke of 92 mm (an effective radial stroke with attachments fitted at a 60-degree angle of 80 mm) and a copying length of 420 mm. The turret was fitted with an automatic stop for 6 cuts: 4 roughing and 2 finishing

Hydraulic Copy Attachment 125-53.800 by Sauter: Model KMC-5. This unit had slide stroke of 52 mm (an effective radial stroke with attachments fitted at a 60-degree angle of 45 mm) and a copying length of 420 mm. 5 cutting passes were provided for controlled by a manual turret stop. This assembly was supplied complete with 1 basic toolholder, 1 external-copying toolholder with a 12 x 18 mm opening; 1 internal-copying toolholder with a 12 x 18 mm opening; 1 dial indicator for setting to diameter within 0.01 mm, 1 base and 2 supports for master equipment.