Built by Heidenreich & Harbeck of Hamburg, the smallest models in the VDF range were the 18RO 21RO, and 24RO with centre heights of 7" ((180 mm), 8.25" (210 mm) and 9.5" (240 mm) respectively. The 18RO and 21RO could be had with between-centres capacities of 500, 750, 1000, 1250, 1500 and 2000 mm (19.625, 29.5, 39.375, 49.25, 59 and 79.75 inches) and the 24RO could be ordered with one extra length capacity of 2500 mm (98.5"). Long-bed versions were fitted with a third foot in the middle of the bed to prevent sagging when under a heavy load
While the RO18 and RO21 were designed and built to handle work within their size capacity, the RO24 was a "stretched" version intended for larger, lighter or more awkward jobs where rates of metal removal were not an important factor - with the added benefit of freeing up heavier machines in a busy shop for their intended purpose. However, although otherwise having the same general specification of the smaller models, the 24RO was, to help its intended purpose, equipped with a stronger saddle and cross slide.
Both standard and models with increased accuracy were available, the latter to the DIN standard 8605 but on straight-bed lathes only (i.e. without a gap) and up to 39 inches (1000 mm) between centres These superior models could be had with or without a high-precision leadscrew, this being made to a guaranteed maximum pitch error of just 0.0008" or 0.0004" over 12 inches (0.02 mm or 0.01 mm over 300 mm) Whether the increased accuracy was the result of more careful machining and assembly - or just the selection of the most accurate machines from a standard production batch (as Colchester did with some of their lathes) is not known, but, being a cynic, the writer would suggest the latter as being more likely.
First in the range to be put on the market was the RO18, introduced during the late 1940s followed by, in the very early 1950s, the RO21 and then the RO24. The lathes remained largely unchanged until around the early 1960s when numerous improvements were made (and model designations changed as already mentioned), these including an increase in weight of around 8%, the fitting of needle-roller bearings in place of plain bushes on shafts - such as lever pivots - and modifications to the headstock and its lubrication system.
Motor power varied, the makers suggesting from around 5 to 10 h.p. being necessary, the early standard models listed as needing 5.5 h.p. while publicity material hinted that later versions really needed 7.5 h.p. Fitted with a No. 4 Morse taper on all versions, on early models the headstock spindle was bored through 50 mm and fitted with a DIN800 threaded nose, later machines being larger at 56 mm and usually found with the much more supportive and safe short-taper DIN 55022 - this version using the same angle as the well-known American-designed CamLock type.
While it is believed that the models made in the 1940s and early 1950s had two plain spindle bearings, all others had a double-row taper roller at the front and a single row at the rear - though the option did remain to have an adjustable plain bearing at the front; axial thrust being taken by a ball race. Gears built into the headstock were in a heat-treated, ground-finished alloy steel and held on multi-spline shafts running in roller bearings. Control was by two levers, one mounted on the headstock, the other pivoting from the right-hand face of the apron and travelling with it. Both levers were of the "safety" type i.e. they could not be accidentally nudged into engagement instead, they had to be pulled away from a spring-loaded, indented position before being turned to start the lathe. Forward and reverse drive was through a multi-disc clutch with, for stopping, a band brake, this simple device being replaced on later models by a much more effective, powerful and automatically applied electromagnetic type that could bring an unloaded spindle from maximum speed to a halt in around two seconds. Spindle speeds varied over the years with a typical, early specification, being twelve in a choice of three ranges: 17 to 750 r.p.m., 23.5 to 1050 r.p.m. and 33.5 to 1500 r.p.m. At extra cost two high-speed set-ups were also available, both requiring a more powerful motor of up to 10 h.p. The catalogue specification of the first type gave a range 45 to 2000 r.p.m. while the second, not listed in the charts, ran from 1400 to 4000 r.p.m. and was described in the text as "Special" and intended for "...the use with ceramic tools or the machining of materials such as copper and plastic." Rather unusually, the headstock's front bearing was air cooled by a fan carried on the spindle with filtration taken care of by three units mounted at the left-hand end of the headstock - these being similar to the oiled wire-mesh filters found on compressors or, typically, on cheaper two-stroke motorcycle engines as made until the 1960s.
To bring the feed and screwcutting rates into a usable range, the slower of the two high-speed versions had the ratio of the changewheel gearing to the screwcutting and feeds gearbox halved, while the "Special" had no screwcutting facility at all - and also lacked the spindle-reverse mechanism. Motors could be flange mounted against the outside left-hand face of the headstock, or foot mounted at the back of the headstock-end bed plinth - drive to the headstock input pulley being by three V-belts. Lubrication was taken care of by a pressure pump that distributed filtered oil through pipes to the required locations - earlier machines being fitted with a centrally-positioned manifold above the gears from which the pipes ran; later models lacked the manifold and had revised pipework..