Also produced as a plain-turning lathe, the expensive and complex 120-VM was, when introduced during the mid 1940s, the third of Schaublin leadscrew screwcutting lathes following the pre-war 102 mm centre height Model 102-VM and 130 mm centre height Model 130-VM.
With a centre height of 120 mm (4.7 inches) and a between-centres capacity of at first 500 mm (20 inches) but later 600 mm, the lathe was intended for toolroom use and had a bed arranged in a manner similar to that employed on the 102-VM - the front wall being extended to carry a V-way and the rear wall a rectangular way on which the carriage ran - but (unlike the 102-VM) with the bevelled-sided top altered so that the tailstock ran on its own flat and V way. In a similar fashion there was a rear "saddle" joined to that at the front by a section beneath the bed (that carried the leadscrew clasp nuts) so forming a rigid cage around the bed.
One unusual feature of the lathe was a continuously-variable drive system working through a 1 : 5.3 ratio backgeared (oil-bath) headstock and driven by a 2-speed 1.5/2.7 h.p. motor running at 715/1410 r.p.m. on late models and 750/1500 r.p.m. on earlier. The variable-speed unit was interesting (and resembled that used on some early primitive "cyclecars") where a friction disc was made to rub against a conical face with the ratio being changed by altering the radial position of the contact point. Needless to say, the Schaublin unit was beautifully constructed , worked smoothly and with the face friction material lasting several years before replacement was required. Drive to the headstock spindle was by a flat belt that ran over a pulley supported at each side in its own ball races; with the drive transmitted from pulley to spindle through a peg all effects of belt pull were thus removed and the spindle had to take only those loads imposed by the cutting process. Spindle speeds spanned approximately 50 to 1750 r.p.m. and were altered by a large handwheel on the front of the stand in combination with a lever on the headstock and another - connected to a control rod - on the apron. To select a spindle speed the large wheel was turned until the desired reading appeared on a dial immediately above it; at the side of the dial a conversion chart indicated the correct setting for the two levers. Power sliding and surfacing feeds were separate from the screwcutting mechanism and driven by V-belt to a power shaft set along the front of the bed - the pulleys being contained within a housing, covered by a hinge-open cover, on the front face of the headstock. Feed rates were selected, on early machines, by a headstock mounted lever - later changed for a dial that carried red and green segments indicating the rates together with a central push-pull button that gave neutral when set centrally, a fast range when pushed in - 0.13, 0.20, 0.32 and 0.5 mm and a slow when pulled out - 0.025, 0.040, 0.060 and 0.095 mm. Power cross-feed rates were set at half those of the sliding: 0.012, 0.02, 0.03, 0.05, 0.06, 0.10, 0.16 and 0.25 mm. However, on early examples of the lathe the range of feeds was much more limited: 0.025 to 0.172 longitudinally and 0.010 to 0.068 across. On all versions of the lathe a lever on top of the feeds box was used to reverse the drive - it could be moved safely at any speed with its middle position acting as a neutral - and by swapping over the drive and driven pulleys in the box beneath it the rate of feed could be halved.
Taking W25 collets the 25 mm bore, No. 2 Morse taper  headstock spindle offered a little more capacity than the W20 collet size of the contemporary 102. Spindle bearings were of the highest quality with that at the front being a double-row cylindrical roller (usually an SKF NN 3011-K-SP) and at the rear two ball bearings of the "magneto type" (SKF 7208-C15).
Screwcutting was by a set of 24 changewheels through a tumble-reverse mechanism (with, unusually, two separate arms to carry the gear) and a massive leadscrew set down the centre line of the bed that was grasped by positively-lubricated clasp nuts positioned almost exactly beneath the toolpost. Metric pitches varied from 0.25 to 7 mm and English from 60 down to 4 t.p.i. Module pitches from 0.25 to 4 could also be generated.
Using a typically Schaublin design the compound slide rest featured a full-length cross slide, with two rear-mounted T-slots, and a long-travel, twin-T-slot top slide that, because it had plenty of clearance, was able to be fitted with an unusually large micrometer dial.
Although of limited size the 120-VM was very heavily built - it weighed in excess of 850 kg - and was mounted on a rectangular-form cast-iron cabinet with a built-in chip tray and electrical equipment..