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Mondiale Celtic 14 Lathe
Mondial and Simplex Manuals are available from store.lathes.co.uk

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While the 7.28-inch centre height by 20, 30, 40 or 60 inches between-centres Mondiale Celtic "14" was, in terms of its design, almost identical to the 6-inch centre height Model "12" it was not just the same machine with an increased centre height but a completely re-engineered lathe that carried over only a few minor parts. It was intended for heavy-duty use in industry and repair workshops and, when fitted with the optional bed-mounted capstan unit, for light production work as well. It was mounted on two heavy cast-iron plinths spanned by a deep slide-out chip tray; unfortunately there was no form of storage, not even an open shelf, for either tools or accessories.
The headstock was divided (and stiffened) by two internal walls into 3 compartments: that nearest the spindle nose contained the oil-bath lubricated reduction-gearing set (with an unusual male and female "sprocket" engagement); the centre part held the V-belt drive pulley and was sealed to keep the belts oil free while the left-hand section was devoted to the oil-immersed "reversing" gears that drove the train of screwcutting changewheels.  At 1
3/8" the bore of the No. 5 Morse taper headstock spindle was rather small - on the 7-inch Colchester Triumph it was 2" - but it ran in Timken taper roller bearings and was driven by 2 V belts from a 4-speed gearbox mounted inside the left-hand cabinet plinth. For the standard lathe the spindle nose was a 5.5 mm pitch 60 mm-diameter thread but for the high-speed version the safe and effective (and at the time very popular) American long taper in an L0 size - two sizes below the much heavier-duty L1 size fitted to the Triumph. The spindle-speed gearbox was operated by an large chrome-plated lever on the font of the stand and fitted with oil-splash lubricated, induction-hardened gears running on ball-bearing supported, hardened and splined shafts. Bolted underneath the gearbox was a push-button controlled electric motor with 2 speeds as standard; for the faster of the two spindle-speed ranges this was a 3/1.9 HP unit and for the slower a 2/1.6 HP; combined with the single-lever-operated headstock-mounted reduction gearing the drive gave a total of 16 speeds from 24 to 1000 rpm on the standard lathe and 38 to 1600 rpm on the high-speed version.
Strangely, although the smaller model 12 lathe was offered with a powerful foot-operated spindle brake, no such option as available for the 14L a situation that must have frustrated many operators as they watched their bonus-payment seconds slip away because a 100 lb lump would not stop rotating quickly enough.
The V-way bed could be had with, or without, a detachable gap piece that allowed material up to 21.25" inches in diameter and approximately 4" in thickness from the faceplate to be swung. The V-ways were of a design similar to that first used on the beautiful American Wade No. 7 precision bench lathe where the (asymmetric) front V was both laid back at a shallower angle than normal and made especially wide;  the rear surface was narrower and, in order to better absorb tool thrust, set at a steeper angle.  Although not hardened (a process restricted to the extensive options' list) the bed was of robust construction and relatively deep in relation to the machine's centre height.
With every thread or feed selection made by rotary levers (and a consequent absence of sliding controls) the oil-bath screwcutting gearbox (with hardened gears) could be completely sealed against the ingress of dirt and swarf. By using just the ordinary set of changewheels the box was able to generate 54 English pitches (from 96 to 1
5/8 t.p.i.) and 27 metric (from 0.25 to 10 mm pitch) - a range superior to the 45 English and 12 metric of the Colchester Triumph. The sliding and surfacing feeds totalled 54 from 0.0027" to 0.144" per revolution of the spindle on longitudinal travel and from 0.00135" to 0.072" on the cross feed. With a different changewheel set on the quadrant arm a complete range of diametral and module pitches could be produced and the 5-segment screwcutting chart included these thread sets in its layout. The 4 t.p.i. leadscrew was ground finished for accuracy and its bronze engagement clasp nuts adjustable for backlash; the power feeds were taken to the apron by a separate keyed shaft working though a torque-limiting coupling that also, very usefully, permitted work to be turned against stops.
With its double-wall construction, oil-bath lubrication and ingenious mechanical design the all-helical-geared apron was well engineered for its task - and of the type also used throughout the Celtic range. The drive shaft from the gearbox transmitted its power through a worm and wheel to a shaft that passed vertically though the centre line of the casting; at the top of the shaft a double-sided dog clutch (operated by a very large combined selection and engagement quadrant lever on the face of the apron) moved up or down to select power surfacing and sliding feeds respectively. Although the apron was a robust and reliable piece of engineering its feeds engagement mechanism suffered from the usual drawback of all quadrant-lever operated systems: the awkward double action of pulling out the location plunger and swinging the operating arm sideways meant that an instant (and certain) disengagement of the feeds was impossible. A simple flick-in-and-out lever, working in a vertical plane between fixed positions (and through some sort of overload protection), would have been much preferred in this situation. The right-hand face of the apron provided a pivoting point for a lever that operated a spindle reversing switch - a useful safety feature, especially on longer bed versions where the operator could be at some distance from the headstock-mounted push buttons.
Entirely conventional (though without T-slots in its top surface) the saddle carried a compound slide rest with proper taper gibs that were adjustable, with the usual sensitivity, by a push screw at the front and a stop screw at the rear. Two cross slides were available, both with a travel of 9.25": a plain-top standard version version - unfortunately shorter than the slide that it ran on and with a cast extension cover at the rear to protect the feed screw - and a full-length T-slotted one able to accommodate a rear-mounted toolpost, its support block and other accessories. The top slide could be rotated only 45 degrees in either direction but came complete with an indexing (though 8-positions) 4-way toolpost.
The tailstock was, perhaps the weakest point in the lathe's specification for, although the (unhardened) 1.875"-diameter No. 4 Morse taper barrel was  "microfinished" its travel was short at 4.344" and the clamp nut required a loose spanner to operate - the latter gambit may have saved the makers money but was guaranteed to waste time in the customer's workshop when the spanner was inevitably "borrowed" for some other task. The top section of the tailstock could be offset in the usual way for taper turning and had a maximum movement of 3/8". The weight of the lathe varied with the between-centres capacity as follows: 20" 1600 lbs; 30" 1765 lbs;  40" 1875 lbs;  50" 1930 lbs..

7.28-inch centre height by 20, 30, 40 or 60 inches between-centres Mondiale Celtic "14"


Celtic 14 lathe headstock internals with the slow-speed "backgear" engaged - the dog-clutch has been slid forwards into engagement with the Bull Wheel.

The re-positioned drive system shows that the "14" was not just a "12" with an increased centre height but a completely re-engineered lathe that shared with it only a few minor parts. 


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Mondial and Simplex Manuals are available from store.lathes.co.uk

Mondiale Celtic 14 Lathe
email: tony@lathes.co.uk
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