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Continued:
The headstock on the Mk. 1 had a very deep, lift-off cast-iron cover and used a 0.5-inch bore spindle with a 1.5" x 6tpi nose running in plain bearings with speed changes by two separate quadrant levers mounted on front face of the headstock. On the Mk. 2 the headstock was strengthened with a more rigid casting helped by a much smaller top-mounted bolt-on inspection hatch: the spindle ran in ball or roller bearings, was increased in size to carry a 1.75" x 6 tpi nose thread and had a more useful 3/4-inch bore; the speed-change levers, being mounted concentrically on a common shaft, were easier and quicker to operate - though one had to be aware that, except for their ball-indents, these much more vulnerable levers had no locks and were much more likely to be accidentally struck and moved.
The customer was offered the option on both lathes of either a self-contained or external drive. The built-on drive system had the motor fastened to an adjustable platform on the back of the headstock-end plinth with drive to the headstock from a 0.75 hp 3-phase AC or DC motor by twin V belts through a standard-fit clutch. The flat-belt machine was designed to take its power from a remote countershaft, or overhead line shafting and, to simplify setting up in the workshop, came complete with a neatly-engineered headstock-mounted fast-and-loose pulley system that took a 1.25"-wide belt.
Although the screwcutting arrangements were completely redesigned on the Mk. 2 both machines used a 1-inch diameter, 4 t.p.i. leadscrew with a separate 5/8"-diameter shaft to provide power sliding on the Mk. 1 and both sliding and surfacing feeds on the Mk. 2. Each version could be had with changewheels for screwcutting but the simple 2-lever, 3-change feed-box on the Mk. 1 gave way to a more complex assembly on the Mk. 2 that, strangely, offered no more speeds but an improved action and a lever to change instantly from screwcutting to power feeds. No tumble reverse was fitted instead both gear boxes contained a reversing mechanism by which means the carriage could be moved in either direction. The standard set of changewheels comprised: 20, 25, 30, 40, 50, 65, 66, 70, 76, 80, 90, 100, 120, 125 - and a 127 metric translation wheel and was able to generate inch pitches from 2 to 28 tpi and metric from 1 to 10mm .
On both lathes the 10-inch-long saddle and double-wall apron were both massive affairs, beautifully engineered with, on the Mk. 1, a two-position quadrant lever to select the sliding feed and a screw-in handwheel to engage it (and thus, unfortunately, no way of immediately releasing the drive). On the Mk. 2 the same quadrant lever selected either sliding or surfacing feeds with engagement taken care of by flicking up and down a separate lever positioned on the right-hand apron wall. A spring-loaded slipping clutch was fitted to the feeds shaft between the apron and gearbox on the Mk. 2 - not unlike that used on Harrison L4 lathes - to protect both mechanisms from excessive loads and to ease sudden shocks.
Denham Junior beds were always unhardened , 41/2"- deep and constructed in a "half-box" form. On the Mk. 1 the bed was of traditional "English" pattern with a flat top, 60-degree sides and an "open" gap without a capping section. On the Mk. 2 a dramatic change was made to V-and-flat ways and the gap provided with a bolt-in bridge piece to better support the saddle when working close to a faceplate. . With the gap bridge removed the lathe could turn a piece of metal 15.5" in diameter and 4" thick.
The lathe was supported on a cast-iron box-cabinet under the headstock end (on the inside face of which the electrical control gear was inconveniently and dangerously sited facing sideways rather than outwards) and a simple leg beneath the tailstock; a steel chip tray was standard equipment - when many makers of the time tried to charge extra for this very ordinary, cheap but useful piece of equipment.
A weak point on the lathe was the tailstock - a simple set-over affair fitted with a No. 2 Morse taper barrel, graduated in fractions of an inch, and a crude slot in the casting with a screw clamp to distort it and lock the barrel (a horrid feature, but one found even on some very expensive Swiss Schaublin lathes) - whilst a loose spanner had to be hunted down to lock the unit to the bed.
A machine with strong similarities to the Denham was made by a company with what have been the strangest-ever name for a machine-tool manufacturer, "Keighley Lifts" - who origins were, naturally enough, in the lift-making business. At the beginning of WW2 Keighley Lifts produced a badged Denham clone for the Ministry of Supply (most of which ended up with the Army). One machine which may have differed from the normal production run was a version of the Mk. 2 that used a plain-bearing headstock; it is understand from a former Keighley employee that most of these Air-Ministry 'specials' were (after use in the 1950s Kenya insurgency) sold on to the Australian Defence Force. Production of the Junior appears to have been helped by other manufacturers as well, examples having been found with "Henry Milnes" cast into their beds - this well known lathe maker being another member of the once thriving Halifax machine-tool community..
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