Typical of the pre-WW2 LeBlond lathes was the 17" Heavy Duty. Available in both open-belt and geared-headstock versions it was almost identical in appearance to both  smaller and larger

On LeBlond Lathes of 15" to 23" capacity, the front and rear spindle bearing were of different construction. The front bearing, being the more heavily loaded of the two, was formed by shrinking a hardened-steel sleeve onto the spindle and then finish grinding it in position. The bearing then ran directly in the cast iron of the headstock - an ideal combination of surfaces for long and reliable operation. The left-hand bearing, being much less heavily stressed was formed from traditional "babbit " bearing metal. LeBlond claimed that the two bearings would wear at the same rate, and so keep the spindle in as near perfect alignment as possible - however, they did acknowledge that both the design and material specified for headstock bearings were contentious matters - and were therefore prepared to supply disbelievers with either phosphor bronze or babbit bearings as required.

"Single-Pulley Driven Headstock" - an internal view. The geared headstock provided twelve spindle speeds, with the use of thirteen gears, all of which were made of nickel-alloy steel, heat treated and hardened- - the bores being ground concentric with the pitch circle after heat treating to ensure that they ran as quietly as possible.
The headstock components were of robust proportions, the gears being unusually wide faced and of large diameter. 

On the open flat-belt drive headstocks LeBlond employed a form of clutched double backgear which, once engaged, could be instantly changed between the two low-speed ratios by the single stroke of a lever. This gave the lathe three speed ranges: open high, intermediate low and slow.

On the very largest LeBlond lathes of 33" and 36" capacity, a "Triple backgear" was offered that was, in effect, a backgear built onto a backgear. This arrangement enabled the lathes to run not only at the high speeds necessary for smaller work, but also at the very low speeds which the cutting tools of the day demanded when taking heavy cuts on the largest diameter the lathes could accommodate.

Massively constructed, the bed of the LeBlond lathe featured a much steeper angle to the front way than that provided by other makers - this was designated by the makers as their "Improved Compensating V" and was claimed to overcome the limitations that were evident in the standard American inverted V arrangement with its equal-sized ways of very limited area. The back of the carriage ran on a flat way (and was retained by a flat gib underneath, copying "English" practice) whilst the top of the front ways were exceptionally broad and the Vs arranged at 15 degrees and 70 degrees which, it was claimed,  prevented the carriage from trying to climb over them under heavy cuts.

Heavily-built LeBlond 25" lathe of 1921 clearly showing the bed section with its steeply-racked, wide-surface "inverted V" construction. Note the rack-driven tailstock - no need to send for two apprentices to push it along the bed.
Like many makers of the time LeBlond seemed content to fit what today would be considered very undersized micrometer dials to the compound-slide feed screws.

A box-section casting was used for the LeBlond apron, a design that supported the various gear-carrying shafts at both ends. Tongued at both ends for accurate location, the Apron was fastened to the saddle with four bolts. All gears were machined from drop forgings and their shafts hardened and ground. A single, positive-action lever with a spring-plunger indent moved though a quadrant to engage either power sliding or surfacing - and the feed could be instantly tripped in or out by another lever mounted centrally on the apron front.
Leadscrews were roughed out on a threading lathe and then allowed a period of time for the strains caused by machining to equalise; they were then finished on a lathe fitted with a precision master screw. Because a separate power shaft was used for sliding and surfacing feeds, the accuracy of the leadscrew was not destroyed in day-to-day work.

If there is one feature that immediately makes a LeBlond lathe recognisable it is the "barrel" selector" screwcutting gearbox . The basic design was used from 1920 onwards across the entire range from 10" to 25". It was a very compact unit, using a barrel and quadrant lever on the larger lathes - and the barrel together with a horizontal lever and sliding "Norton" type gear on the later 10" Regal. By WW2 the lathes of  17" and above were fitted with a modified design with a top lever of a more conventional appearance.

The LeBlond "Portable Engine Lathe" was made in 15", 17" and 19" swing versions and advertised as being suitable for use in "railway workshops, arsenals and battleships" - though one hopes that a method of locking the wheels was provided for when sea conditions were other then a flat calm …..

Although not specialising in the type, LeBlond also produced a lathe advertised as a "Toolroom" model. Any lathe in the range could be supplied to this specification which, besides selective assembly also included a range of options including taper turning, draw-in collets, coolant and chip tray and a relieving or backing off attachment.

LeBlond "Style D" motor mount.
A very early installation of an integral motor drive unit on the back of a lathe. Quite why it took so long for this neat, space saving deign to be adopted  by all lathe manufactures is a mystery.
Makers of lathes with open, flat-belt drive headstocks who hesitated to develop geared-head machines, yet wanted to include a self-contained machine in their line, had little choice but to mount individual electric motors and their countershaft above the spindle line so making the lathes even more top heavy and cumbersome in appearance.
With the coming of V belts compact, short-centre drives were possible and proved very popular for commercial installation running production machinery - although the machine above used not a belt, but a "Morse Silent Chain". Some toolroom lathes, however, continued to rely to this day upon the much smoother running flat belt. 

Copying Attachment. This followed the usual design but, instead of the tracing tool being kept in contact (with the shape to be copied) by hydraulic power as on more modern lathes, a very heavy weight was used, suspended by a cable over pulleys and operating through the cross-feed screw. The weight was stationary, and so relieved the carriage of extra weight, whilst the thrust from the cut was taken on two heavy studs pressed directly into the carriage casting.
Produced as a flat plate, the form to be copied was bolted to an angle bracket on the rear of the lathe bed; the bracket was adjustable though a small arc to allow for final setting of the work after trial cuts had been made.

"Double Screw" American pattern toolpost mounted on the standard compound slide rest. This heavy-duty tool holder was specified as standard on the 21" and larger machines

"Double Screw" American pattern toolpost mounted on a plain cross slide - an ideal set-up for heavy-duty plain work where the inherent flexibility of the top slide was eliminated by not using it …..

An alternative to the Plain Cross slide was the "Round-block Toolholder" which converted the standard cross slide into a similarly robust unit suitable for heavy turning.

Rise and Fall Slide Rest and Toolpost
Once the tool was locked into its holder, its height could be finely adjusted by means of the ramp-mounted slide. A thread-chasing stop (illustrated) was available as an extra.

This very unusual toolholder, the "Full Swing Rest" was designed to be clamped to the wing of the lathe saddle and, as it name implied, enabled the maximum turning capacity of the machine to be used.
It could also be used in conjunction with the regular toolholders when it was required (or possible) to turn two steps at once.

One way of getting a reasonably-sized cross-feed dial was to specify the very unusual "Multiple Positive Cross Stop", which was available as an extra on any lathe up to and including the 36" swing model.
The stops were built into the cross-feed dial housing - which had to be exceptionally large to accommodate the mechanism - and provided with adjustable indicator clips for quick reading.
The stops consisted of four hardened and ground discs, each with a projection on its periphery, which engaged against pins which can be seen protruding through the body of the housing.
The discs could be adjusted to engage the stop pins at any predetermined distance from .001" to one or more full turns, after which they were locked together by wing nuts at the front of the hand wheel. It was claimed that the stops would duplicate diameters to within .001".

While one of the most useful features any lathe can possess is an automatic, pre-set trip for the power feeds the LeBlond "Multiple Automatic Length Stop" went one stage further - and offered rapid and accurate turning of multiple shoulders.
The bar that carried the trip stops was bolted to the front of bed; the tripping mechanism was located in the apron itself and consisted of a hardened-steel clutch which engaged and disengaged the feed mechanism.
The trip lever for the automatic stops was put in a downward position and the feed engaged. The carriage then feed along the bed until it engaged the first trip dog, which threw out the drive. The drive was then re-engaged and the operation repeated for any number of shoulders as stops were provided for.
If the lathe was also fitted with the Multiple Cross Stop then different diameters could easily be preset for each "trip" - and much time saved.

The "Multiple Positive Length Stop" was for the accurate, pre-set spacing of shoulders on long bars. The spacing bar and holder were attached to the carriage and the spacing lever adjusted along the front shear of the bed and clamped in any desired position. The bar was made up with the required number of  "notches" spaced so that they corresponded to the shoulders required on the shaft to be turned. When the work was finished the shaft could, of course, be removed and preserved for future repetition of the job.
When the bar was not being used it could be given a half turn - so that the spacing index lever did not engage with the slots - and the lathe used normally.

Designed to do under power what had previously been done by hand the Relieving Attachment was used to accurately relieve (or back off) the teeth of taps, cutters, hobs and milling cutters. The device was fastened to the top of the gearbox and power taken from a gear on the end of the headstock spindle and then through interchangeable gears carried on a quadrant arm. The unit could be left in place - and did not interfere with the normal operation of the lathe.
The drive passed through two knuckle joints, and a telescopic shaft, to the actuating mechanism which consisted of a hardened and ground cam, carried between bronze bearings in a compound-swivel rest, which moved against a hardened steel roller carried in a sliding compound rest nut. The cam gave the standard top slide a push forwards and a heavy coil spring pushed it back, so imparting an oscillating motion to the slide. The return spring encircled a rod, attached to the sliding nut, and had two adjusting nuts at either end by which the amount of relief needed could be adjusted.
The adjusting nuts were also used to draw the compound rest nut and roller away from the cam and hold it solidly against a finished surface and, because the cam then revolved idly and the top slide remained stationary, the top slide could then be used in the normal way.
The number of flutes that could be relieved with the changewheels supplied were 2, 8, 4, 5, 6, 7, 8, 9, 10, 11, 12, 18, 14, 15, 16, 18, 20, 22, 24, 26, 28, 80 and 82 with the different gear combinations shown on an engraved plate. This attachment was designed to be factory fitted to any LeBlond lathe from 15" to 21" swing.