A later Model EE with the rectangular screwcutting chart on the face of the headstock.
By 1945 the swing had increased a little to 12.5 inches and a longer bed was listed (which, surprisingly, did not prove popular) admitting 30 inches between centres. Modifications to the screwcutting gearbox resulted in an improvement to 50 feeds (from 0.0005" to 0.016") with the threading range extended to cover 60 threads from 3 to 184 t.p.i. In 1970 further mechanical modifications were made including the fitting of a combined English/Metric screwcutting gearbox and beautifully finished dual English/metric compound-feed dials. The English/metric gearbox could generate 60 English pitches from 3 to 184 t.p.i and 50 metric from 0.25 mm to 11 mm.
With a standard spindle run-out of less than 40 millionths, and 30 millionths being an option (denoted by a headstock badge) the 113/32" bore headstock spindle runs in super-precision angular contact ABEC5 hand-matched, 60 mm ID bearings with the front being a non-standard and very expensive type fitted with a flange. The spindle is sleeved with an adaptor bush from its standard No. 12 Jarno to a No. 2 Morse taper and carries a 3"-D-1 Camlock nose with, as one useful option, an adapter unit containing an indexing gear and graduations to assist in the cutting of 2, 3, 4, 6, and 8 multi-start threads. Fitted with a substantial mechanical lock to ease the removal of chucks, the spindle is also provided with two safety devices: an electrical interlock to prevent it from running if accidentally engaged and a "Hi-lock" to prevent the engagement of backgear above 250 r.p.m. However, these features were only fitted on 'square-dial' machines, the 'round dial' having neither. Although the motor could be "plug reversed", that is, instantly changed from one direction of rotation to the other, this was also limited to no more than 250 r.p.m., a relay in the DC control box (called the anti-plug relay) pulling in and refusing reverse until the spindle stops.
Spindle-speed ranges have varied over the years with the option, on earlier lathes, of either 25 to 2000 rpm, 40 to 4000 rpm and another with a maximum speed of 3500 r.p.m. (though just the higher set was available on later machines). There were no mechanical changes to the models, the only differences between them being the use of different diameter belt sheaves (pulleys) and recalibrated tachometers. All versions of the lathe have been fitted with the 5 : 1 reduction gearing that, on later lathes, gives 8 to 800 rpm; because the gearbox is mounted on the motor (in the cabinet base) the headstock spindle is completely isolated from whatever vibration effects the drive might create. On early lathes the headstock-mounted tachometer was mechanically driven by a gear on the spindle (the only gear in contact with it) and could read in forwards rotation only. Later models were given an improved electrical counter able to read with the spindle running backwards.
As a point of interest it is not recommended to increase the top speed on 'round dial' machines. These have a headstock divided into three compartments: one each for the front and rear bearings and one for the gearbox. The bearings are lubricated by the simple expedient of letting them sit, partially submerged, in a oil bath - a system adequate for slower running, but not for continuously high r.p.m.. Later revisions saw the headstock opened up into one cavity and a splash system, together with pipes, used to carry oil direct to the bearings. The leadscrew and its drive gears are used only for screwcutting - the power for sliding and surfacing feeds being fed from the headstock to the gearbox by a flat, endless belt, driven from the end of the headstock spindle and tensioned by a jockey pulley. In standard form (and bearing in mind the differences between the older and newer models) 60 English threads are available of: 3, 3.25, 3.5, 3.75, 4, 4.5, 5, 5.5, 5.75, 6, 6.5, 6.75, 7, 7.5, 8, 9, 10,11, 11.5, 12, 13, 13.5, 14, 15, 16, 18, 20, 22, 23, 24, 26, 27, 28, 30, 32, 36, 40, 44, 46, 48, 52, 54, 56, 60, 64, 72, 80, 88, 92, 96, 104, 108, 112, 120, 144, 160, 176 and 184 t.p.i. Carriage feed rates vary through fifty changes from 0.0005" to 0.016" per revolution of the headstock spindle. A combined English-metric gearbox was also built and offered as an optional extra. It is possible to cut metric threads on the ordinary lathe, but only by unbolting the cover over the automatically-lubricated gear train and substituting the appropriate translation gears.
A masterpiece of precision construction, the apron is carefully laid out for ease of use - though English readers may quibble about the positioning of the carriage-traverse handwheel at the left-hand side where the operator's hand can be showered with hot chippings. Power sliding and surfacing feeds are each selected by their own instant-action, lever-operated clutches: flicking a control up engages the feed with a downward motion to disengages it.
Of silken smoothness, the compound slide rest assembly was fitted with appropriately large and beautifully engraved dials that indicated the number of thousandths of an inch being taken off diameter - not the travel of the slide. The dials' chrome finish was softened by vapour blasting to give an anti-glare effect.
A wide range of accessories was offered and very few 10EEs came without a taper-turning attachment - the details of which varied: some having vernier scale adjusters with graduated dials - just like the English CVA lathe - others came with a "bolt-on" brass gear to turn. While a convenient and quick-to-operate telescoping cross-feed screw was available strangely, for this class of lathe, a fixed type was also supplied that required the screw to be removed before the unit could be brought into action. In addition to the usual fixed and travelling steadies, a variety of collets and collet holders, it was, at various times possible to specify dual inch/metric feed-screw dials, a rear dovetail and tool block on the cross slide, a (very rare) multi-position cross-feed micrometer stop and the previously-mentioned dual inch/metric screwcutting gearbox.
At times, compared with the greatly sought-after Hardinge HLV and HLV-H 12" x 20" toolroom lathe, the 10" EE Precision was (unaccountably) often underrated on the used market and available at a much more reasonable price. Today, with such a restricted choice of new machines, the market for this type of lathe is very much alive with a good trade in rebuilt machines and even new ones - United Airlines, for example, taking delivery of one in August 2000. Although a very heavy machine, at around 3250 lbs, it occupies a floor area of only 29" x 60" - and hence can be easily lost within a corner of the typical American domestic garage.
Although early production figures are difficult to determine (though the factory has records of every one made) since 1955 approximately 8,000 10EEs have been manufactured. In 1946 the base price was $4,194 but by 1955 had risen, with inflation, to $7,400 and reached $9,775 by 1965. Today (2008) they retail at $79,950 - the latter figure, adjusted against the retail prices index, shows it to be not as high as might be expected ($9,775 in 1965 being equal to approximately $59,373 in 2010).
Not only the general layout but also many detail features of the Monarch 10" EE lathe were incorporated in what was, in effect, a copy, the English CVA lathe.
A very rare capstan (screw-machine) version was also built, but in what must have been very small numbers..
*The following was kindly contributed by Mr. R. E. Hartzel of Marine and Industrial Engineering, Moorestown, New Jersey, USA
Monarch Lathe Electron Tube/Valve Control
There were two versions of electron tube/valve control. The early one used nine tubes/valves and the later used three. The workhorse of these controls is a thyatron tube/valve. The thyatron is constructed with three and sometimes four elements contained in a glass envelope mounted on a base with, in the smaller sizes, pins for connection into a socket. However, in the larger sizes, there is a top cap for connection to the plate or anode. In the case of the Cl 6J/5665 there are no pins, owing to the large currents through the unit, but flexible, insulated leads with bolt-on lugs known as "flying leads" Inside the glass envelope are the elements: i.e. heater or filament, the grid and the plate. Some tubes/valves contain a separate cathode close to the heater but most use the heater as the cathode. The heater is supplied with a voltage that causes it to come to a red heat and in doing so causes quantities of negative electrons to be emitted from its surface. The plate, being at a positive potential, exerts an attraction for these but the strongly negative grid between prevents the electrons from reaching the plate. At this point, if the negative grid voltage is reduced to zero and the grid voltage made ever so slightly positive, ionization will take place and the electrons will flow to the plate. The ionization within the glass envelope is enhanced by the presence of xenon gas and in some tubes/valves by mercury vapor - and in others by both. Once the tube/valve "strikes" it can only be stopped by opening the circuit to the anode/plate or when the alternating potential applied to the anode falls back to zero voltage if the grid is returned to a negative potential. In order to accomplish the foregoing, an alternating potential is used on the grid that can be shifted out of phase, or out of time, with respect to the phase or timing voltage applied to the anode. The foregoing imparts a pulsating flow of electrons between the cathode and the anode. The length or duration of the pulses results in a higher or lower value of alternating current being converted to direct or continuous current. This allows finite control of the output voltage resulting in finite speed control of a motor.
Applications for the thyatron have been found in many other areas including light dimmers and the control of electric furnaces and generators. In applying the thyatron to motor drives, there are other circuits which feedback a signal to the grid control circuit. One such circuit being that of sensing the reduction of speed owing to increased mechanical load. When this circuit senses a speed reduction, it feeds back a signal to the grid circuit, thereby compensating the speed loss. The response time of a thyatron is exceedingly fast and measured in microseconds. In conclusion, it would be remiss if I did not include what I consider to be the most important use known to myself of the thyatron, that being in the WWII code-breaking computer named Colossus. Tommy Flowers of the British Post Office Research Station at Dollis Hill, London, designed Colossus for use at Bletchley Park against the German Enigma codes. Tommy Flowers used thyatrons in place of electromechanical relays because their super-fast response time was superior - the need for speed being caused by the vast quantity of traffic to be processed. For those of you who are interested, there is a Bletchley Park web site and a rebuilt (rather a reconstructed) Colossus has recently been installed in the museum there.