Constructed in the style of the already established and very successful 7.5-inch centre height Triumph 2000 and 8.5-inch Mascot 1600, the 6.5 inch (165 mm) centre height Master 2500 (together with its close cousin the Student 1800), continued Colchester's traditional use of two names that had been synonymous with lathes of an almost perfect design and capacity for both training and professional workshops since the early 1950s. As with older Student and Master Models the lathes shared the vast majority of their components and had only small but nevertheless significant differences in their specifications - all of which, in the case of the newer machines, centred on the headstock and drive system. The model number of each lathe referred to its top speed that, in the case of the "Master 2500" was reached by a more refined and stronger system than used on the Student 1800 and consisted of a 3.75 kW (5 hp) motor that drove through 2 V-belts to an instant-acting forward and reverse wet-type multi-plate clutches (made by either Matrix in England or Ortlinghaus in Germany) mounted inside the headstock on the rearmost layshaft. The lubrication of the "Master 2500" headstock reflected the harder work the lathe was intended to undertake (in comparison with the 1800) and was taken care of by an impellor-type pump mounted on a oil tank fitted inside the headstock-end plinth and driven from an extension to the main-motor spindle; from the tank the oil was taken to a "distributor block" fastened beneath the headstock's top cover and from there by pipes to the required locations. A flow-indicator sight-glass was fitted to the front headstock face to allow the operator to check that oil was flowing correctly. On early models the headstock was fitted with an automatic "spring-applied" brake that brought the spindle to a halt when the control on the apron was returned to neutral; later machines used a much more powerful automotive-type expanding brake, controlled by a full-length foot pedal between the stand's headstock and tailstock-end plinths (and interconnected with the headstock clutches) that was able to bring the heaviest job to a rapid stop
The 9.5-inch (230 mm) wide bed, induction hardened and ground-finished as standard, was of the usual Colchester V-and-flat type with separate pairs of ways for the carriage and tailstock. It was available in two lengths that gave either 25 or 40 inches (635 mm and 1000 mm) between centres and both could be had both with and without a detachable gap piece that allowed material up to 19-inches (480 mm) in diameter and 4.5-inch (115 mm) thick to be swung on the (optional-extra) 12 or 18-inch diameter faceplates. Gamet Super Precision taper roller bearings) the 1.625" (40 mm) bore, 4-in D1 Cam Lock nose spindle was especially rigid and had been designed in conjunction with the British Machine Tool Industry Research Association. Not all the gears in the headstock were hardened, only those under the greatest strain, but all were ground finished on Reishauer machines. The headstock casting could be adjusted laterally on the bed, although before altering the factory setting the owner was strongly cautioned to consult the (very comprehensive) owner's manual. 16 speeds were available, from 30 to 2500 rpm and, because of the high top speed and the lathe's ability to mount very large jobs, the makers warned against the use of other than the dynamically balanced, ductile-iron chucks with hardened scrolls that had been specially commissioned from Burnerd; if a new chuck is required on these lathes it would be unwise to fit anything other than one recommended by a reputable Western manufacturer. You are welcome to email for details of quality replacements that we can recommend.
Spindle speeds were selected by a pair of concentrically mounted paddle levers that worked through an ingenious and compact mechanism, with (for a machine tool) an almost foolproof system of colour coding to indicate the settings. Once the motor had been switched on by a headstock-mounted push-button starter the spindle control was by a single lever pivoted from the right-hand apron wall and working through a 'third shaft' parallel and below the feed shaft and leadscrew and connected by links to a cross shaft that passed through the bed just in front of the headstock. Combined with its headstock clutches this control allowed the lathe (which was intended for serious, heavy-duty use) to be started, stopped and instantly reversed while the motor remained running. On the Student 1800, a cheaper lathe more suited to a role as an economical training and repair machine, the control simply switched the motor to forward, reverse and off. The lathe was also fitted with headstock-mounted emergency stop button that operated through the obligatory "no-volt" release (to prevent the motor restarting after a power cut) and a motor-run warning light to alert the hard-of-hearing, or those working in a noisy environment, that things were "active" and the controls not to be casually played with.
Drive to the oil-bath dual Metric/English screwcutting gearbox was by splined 1.5 MOD 20PA "metric" gears. The box was totally enclosed, fitted with hardened and ground gears throughout and operated by three conventional levers plus one that moved through an unusual, 8-position vertical gate. A wide range of pitches and feeds was possible without dismounting or changing any of the changewheels: 39 Metric from 0.2 mm to 14.0 mm; 18 Module from 0.3 to 3.5m; 45 English from 2 to 72 t.p.i. and 21 Diametral from 8 to 44 D.P. The range of sliding feeds varied from 0.001" to 0.040" (0.03 mm to 1.0 mm) and surfacing feeds (at half the sliding rates), from 0.0005" to 0.020" (0.015 mm to 0.5 mm) - all per revolution of the spindle. Both the leadscrew and the powershaft were protected by special shear pins, the specification of which was outlined in the manual with strict instructions not to vary the material used.