By the 1960s, when the new Holbrook "M" range of lathes was introduced, the company was in the hands of Herbert, at the time England's largest machine-tool maker. The "M" range consisted of the 5-inch centre height  "Minor", a 6.125" "Major", the almost identical 7.25-inch "Magna" - and the 8.25" "Marquis". The 'Minor', with a capacity between centres of just 20 inches, was Herbert's smallest centre-lathe and neatly fitted under the market position occupied by makers such as CVA, 'Dean, Smith & Grace, 'Schaublin', Weiler (etc.) and Holbrook's own, larger lathes. The "Minor" - not, perhaps, the most marketable of names - was designed for the "efficient production of small precision components particularly for the electrical and instrument manufacturing industries." Both "early" and "late" models were made, obviously as a result of feed-back from customers, but these were only relatively minor changes that reflected a tidying up of some mechanical details, an improvement in potential reliability together with some easier and more certain operating procedures for the user. That the lathe was superbly built cannot be in doubt - one wag claiming that when the expensive-to-produce design was laid down the accountant must have been distracted by being locked in his office with a particularly-attractive secretary. Every part of this carefully designed machine was built up to a standard, not down to a price, even prosaic covers being in abnormally thick material - that over the motor in half-inch thick cast aluminium and the headstock front-cover extension in 6mm steel with a ground finish.
Of enormous depth, the V and flat-way bed was double-diagonal braced, hardened and ground and supported on a full-length cast-iron stand; being a toolroom-class machine no gap was offered.
Fitted with not only an infinitely-variable spindle-speed drive, the lathe also had independent variable-speed control to the power feeds - along similar lines to the arrangement found on the long-established and popular Hardinge HLV. This arrangement ensured that, whilst the initial settings of spindle speed and feed rate could be at the 'text-book' approved  levels, they could (if necessary) be changed by empirical experimentation until the perfect settings were arrived at for any particular combination of workpiece diameter, material and tool setting. (Another important advantage of this type of drive is that it reduces the number of gears involved in the transmission of power - gear drives are bad news for surface finish, they induce vibrations that, whilst usually hidden in the "roughness" of ordinary turning, become much more evident on the finer finishes achievable on high-quality lathes.) Unlike the Hardinge HLV, where controls were scattered inconveniently around the lathe, on the Hardinge everything was grouped closely together at the headstock end with all but the screwcutting gearbox levers mounted on a heavy, cast-aluminium panel that was, unfortunately, given such a beautifully-finished, stove-enamelled coating that it resembled shiny plastic. From this one panel the electric and mechanical controls were cleverly integrated so the machine could be started in either low or high range, with the brake stopping the spindle and gearbox but leaving the motor and variator running ready for an instant restart. As an alternative, the operator could choose to use a short joystick for spindle direction control - a forward or reverse movement of the lever producing a corresponding direction of spindle and feed-shaft rotation with, in addition, a braking effect produced when moved to the centre and a "spindle-free" position to the right. If the operator wished to bring everything to a halt use of the joystick, than the other controls, caused the spindle, motor and variator to all stop at the same time. So convenient was this joystick arrangement, and so well did it work, that the makers had to caution against over-enthusiastic use, pointing out the damage that could be caused by overloading the electrical system with too frequent stopping, starting and reversing. Later models had the variator control moved to the front of the stand where its isolation made for a slightly safer and surer operation. Because the bed was so large the motor to drive the power sliding and surfacing feeds was able to be mounted neatly out of sight inside it (at the headstock end) with its spindle connected directly to the screwcutting gearbox.
Isolated in a ventilated compartment inside the stand, the spindle-drive system consisted of a large-frame 3 hp, 900 rpm 3-phase motor flange-mounted to an Allspeeds  KOPP swash-plate variable-speed unit with drive by a flexible coupling to a 2-speed gearbox that incorporated separate electro-magnetic "Matrix" clutches (for engaging the high and low speed ranges) together with a third Matrix unit adapted as a brake. All three units sat together on a massive cast-iron plate that could be adjusted to set the final drive belt tension. The speed range was either 80 to 3000 r.p.m. or, optionally, 80 to 4000 r.p.m. (though some lathes, in defiance of the catalogue specification, are accurately marked 100 to 4000 r.p.m.). The final drive to the forged-steel 1.125" bore,  Dl-4" nose headstock spindle (running in precision taper-roller bearings) was by, at first, by multiple V-belts and later a 50-mm wide (10-v) heavy-duty  Poly-V type. If problems are encountered with the electrical controls on a Minor suspect aging of the original selenium rectifiers: however, these are easily replaced by new solid-state types.
On early example of the Minor the speed-change gearbox lubricant was lifted, by a gear pump on the end of the main motor shaft, to the screwcutting gearbox and headstock. Later machines had the oil supply rearranged with the base gearbox retaining its own lubricant (and presumably metal particles with which it would have become contaminated). The spindle speed was indicated on a large mechanical tachometer mounted on the face of the headstock the drive to which, on later models, also powered the oil pump that circulated oil between headstock and screwcutting gearbox.
Continued below: