Constructed in the style of the already established and very successful 7.5-inch centre height Triumph 2000 and 8.5-inch Mascot 1600 models, the 6.5-inch (165 mm) centre height Student 3100 (together with its close cousins the Student 1800 and Master 2500), 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 workshop use since the early 1950s. As with older Student and Master model the two 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 expensive Student 3100 was intended to fill the niche vacated by the long-serving 3000 rpm variable-speed "Chipmaster", a machine that proved so popular its production was continued until 1983. Unfortunately, the appeal of the tough little Chipmaster had always been restricted by its limited capacity: a centre height of 5.5 inches and a capacity between centres of just 20 inches made it suitable only for the smaller tasks in a commercial workshop. The "3100" was designed to overcome these limitations and was not only much larger but fitted with an improved and more reliable variable-speed drive system that employed three "geared" speed ranges; these ranges allowed seamless bands of speeds to be selected between 20 to 120 rpm, 90 to 540 r.p.m. and 500 to 3100 r.p.m. and also ensured that a great amount of torque was available at the slower revolutions. Claimed by the makers to be "maintenance-free" a pair of expanding and contracting pulleys generated the variable-speed changes while a simple gear set within the headstock delivered the fixed speed ranges. The speeds were caused to change by push buttons that activated (limit-switch protected) motors driving threaded rods that caused the pulleys to be moved closer together or further apart - with the "geared ranges" engaged by a single handle integral with a large dial on the face of the headstock. A digital speed display was fitted to the headstock. 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. Once the motor had been switched on by a headstock-mounted push-button starter the starting and stopping of the spindle 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.
Although the lathe was capable of rotating heavy jobs at high speed it was not possible, because of the variable-speed drive system, to fit the same sort of powerful spindle brake that was used on the otherwise very similar Student 1800 and Master 2500 Models. The lathe was, however, fitted with an automatic "fail safe" brake that had a manual release button. Also included was a 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 should not be played with casually.
The rest of the machine was identical to the ordinary Student 1800 and all the accessories for that lathe, and the Master 2500, were identical.
9.5-inch (230mm) wide, the bed was induction hardened and ground-finished as standard; it 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 but wisely could not, because of its size and very high top speed, be ordered with a gap. The headstock gears were lubricated by oil splash, from a supply within the base, with the system improved by the fitting of a "distributor tray" in the roof of the headstock that collected the flung up oil and fed it though pipes to ensure that it reached the right places; the same oil was fed, unfiltered, to the "Gamet Super Precision", pre-loaded and self-adjusting 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.