Dynamically-balanced, the 52 mm (2-inch) bore headstock spindle was made from a high-tensile, alloy-steel forging; it was hardened by a heat-treatment process (giving a reading of 65 to 80 shore along its length), ground finished (including the gear splines) and assembled in a dedicated-for-the-purpose, air-conditioned room. To protect against the ingress of dirt carried in by oil, its bearings were of the grease-sealed, attention-free type. Three bearing were used, all of the specially-selected, super-precision type with double-row cylindrical rollers at each end and a pair of angular-contact type as additional support in the middle. The spindle was bored for a No. 6 Morse taper centre, but normally carried a hardened bushing to reduce this to a No. 4 Morse for regular work; a special "centre push-out bar" was provided by which means the headstock centre, or adaptor sleeve, could be safely removed without recourse to hammering - and the consequential (potential) harm to the spindle's accuracy. The nose was of the Standard American A1-6" type that allowed chucks and faceplates to be bolted very accurately, hard up against the spindle end, as close as possible to the front bearing, and registered there by a short taper. If the time it took to unbolt a spindle fitting was a concern, then an ordinary D1-6" fitting, with its "quick-action" locking pins, was available at extra cost.
A drip-proof 10 h.p. (or optionally 7.5 h.p.) motor was housed in the base of the machine and drove via three V-belts (that passed around two jockey pulleys, one of which could be used to set the tension) to a constant-speed layshaft within the headstock. |Twelve speeds were provided, set so as to cover the majority of the jobs that the lathe might be called upon to perform; cleverly, instead of staying within the conventional geometrical progression, the highest and lowest speeds were each removed from the speed immediately next to them by a factor of approximately 2, this giving, in the standard configuration: 35, 63, 85, 120, 160, 210, 290, 390, 525, 730, 970 and 1800 r.p.m. Three other ranges were optional, one slower and two slightly faster; the slowest range was: 23, 42, 55, 78, 105, 140, 200, 260, 350, 485, 650 and 1200 r.p.m. and the two faster: 38, 70, 95, 130, 180, 240, 330, 440, 600, 810, 1100 and 2000 r.p.m. And: 42, 80, 105, 145, 200, 260, 350, 480, 650, 900, 1200 and 2200 r.p.m.
Spindle speeds were changed by a three-position lever on top of the headstock - this providing High, Low and Neutral positions - together with a simple rotary control on the face of the headstock. The stopping and stating of the spindle was controlled by a third shaft, parallel with the leadscrew and powershaft, and fitted with a lever at the headstock end of the bed and another on the right-hand wall of the apron - a useful safety feature, especially on the long-bed model when the headstock control might have been out of reach.
Screwcutting and power feeds were arranged from a dual metric-English gearbox, pump-lubricated with a filtered oil supply shared with the headstock; the unit was completely enclosed and contained hardened and ground shafts and gears running on anti-friction bearings. Threads and feeds were driven separately, from a leadscrew and power-shaft respectively, and selected by neat, rotary-movement levers, there being no pull-and-slide controls to wrestle with. Sliding-feed rates varied from 0.05 mm (0.002") to 0.7 mm (0.028" ) which was exactly 1/10 of the threading feed rate produced by same position of the selector positions; the power-cross feed rate was arranged to be exactly half sliding rate. Feed direction was selected by a simple push/pull button on the apron and engaged by a lever operating a quick-action, drop-out worm that gave a disengagement action that was light yet positive, no matter how heavy the cutting load at the point of release. The drop-worm and feed clutch were part of a spring-loaded safety-overload mechanism that could be adjusted (by special spanners included in the tool kit) to set the point at which the feeds tripped out before the drive system was damaged. As a safety feature the push/pull feeds' selector was arranged so that, at the end of a longitudinal feed towards the headstock, pulling the button out to engage power cross feed caused the tool to withdraw outwards towards the operator. A very useful fitting (designed to assist with critical finishing operations, changing from roughing to finishing cuts or on multiple-diameter copy work) was a mechanism to halve the feed rates by operating a control lever on the top of the carriage. The direction of the feeds and threads could be reversed through a tumble-reverse-like mechanism controlled by a single lever, situated under the spindle-speed chart on the face of the headstock. Also fitted as standard to the LS, was an automatic knock-off on the carriage longitudinal feed; this system took advantage of the cast-iron stand where a steel rail, let into the front edge of the chip tray, carried a pair of micrometer-adjustable stops that could be quickly slide into any position desired. The stops not only made for accurate and repeatable boring and turning operations but also as a useful safety device with the operator able to leave a long turning job knowing that, when complete (whether moving towards either the headstock, or tailstock), the cut would finish automatically.
32 English threads from 4 to 56 per inch, and metric pitches from 0.5 to 7 mm were available with the change from one to the other by a single lever - whilst the changing of a single 72t gear on the changewheel drive allowed Module and DP pitches to be generated. The 32 mm diameter, 30 degree Acme-threaded leadscrew was manufactured from a heat-treated alloy steel and finished to an accuracy of 0.03 mm per 300 mm (pitch error); it was held in super-precision ball bearings in the tailstock-end bracket and incorporated an end-play adjustment.