Merli lathes were manufactured by Merli Aurelio & C. S.P.A. at Strada per Torrazza Coste, 27050 Codevilla (Pavia) a company founded in Italy during 1917. Over the decades a variety of machine tools types was produced but, by 1976, the range had been compressed to multi-spindle drilling and tapping machines with hydraulic control and automatic cycles, a two-spindle hydraulic facing lathe, the F200 Clovermatic and a number of ordinary geared-headlathes including the Clovis 20/30, 22/33b, 18/27, 22/23. 30/41, 36/47, 70, 150 and, shown on this page, the large "Clovis 50 Standardised Series". Similar in design and layout to the competing Torni FTC Models by Doria S.A.S., the 50 Series was built in two models, the Type 510 (20.0625-inch) and Type 640 (25.1875-inch) - these differing only as to their centre height and with this dimension included in their designation number. Both were available with a wide range of between-centres capacities: 1500, 2000, 2500, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000 and 11000 mm.
Both lathes were built to exactly the same specification and included the same array of features including beds cast from a high-quality Meehanite iron that had been heat treated to eliminate internal stresses, rough planed, allowed to season naturally, rough planed again, induction hardened to between 400 and 500 Brinell, followed by a repeated heat-treatment process and finally finish ground. Deep, rectangular webs braced the front and back walls and a detachable gap section was offered as an optional extra on both the 510 and 640. When fitted, the gap allowed work up to 1310 and 1570 mm (51.56 and 61.33") in diameter and 490 mm (19.3") thick to be turned on the 1000 mm (39.375") diameter faceplate. Bed ways were of the conventional V and flat type - with the front V made much wider and set at a shallower angle on its outside surface than the shorter and steeper inside - the stated aims being to improve longevity while also increasing the ability of the saddle to absorb tool thrust. The bed was carried on a series of integrally cast plinths, each pierced by a hole to allow the insertion of a lifting bar and, between each pair, an easily-removed and very large chip tray supported on castors.
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Headstocks were, of course, all-geared, with the shell cast from a high-strength iron and bolted to the bed. With a 155 mm bore and a No. 6 Morse taper socket, the spindle was machined from a forging in an alloy steel to 15NC11 that was heat treated, case-hardened and ground all over. As standard, the spindle nose was an ASA A2 - though the makers also offered any suitable fitting in the same size range. Supported at the rear in a ball race, at the front the spindle was held in a pair of opposed, 318 mm diameter, high-precision taper roller bearings separated by a distance of approximately 410 mm - the maximum load on the nose being 15 (metric) tonnes (33,112 lbs). Drive came from a 30 h.p. motor mounted in the headstock-end plinth with spindle stop, start and reverse being through double multi-disc, hydraulically operated clutch and combined brake units - the pressure being displayed on a gauge and adjustments to the various setting able to be made externally. Headstock gears were all in a high-grade steel, case hardened and ground. Other gears and shafts within the headstock were all made in a high-grade alloy steel that was heat treated, case-hardened and ground. Shafts ran in high quality ball races with lubrication by a pump that lifted filtered oil from a reservoir in the bed beneath the headstock and then through a system of pipes and unions to all sections of the headstock.
Screwcutting and power feeds were provided by a totally enclosed, sealed gearbox with positive lubrication by a pressure pump. Gears and shafts were all in a heat-treated, case-hardened and ground alloy steel with ball races used throughout. Pitches available as standard - and available without disturbing the changewheels - included 90 Whitworth from 1/2 to 84 t.p.i., 55 metric from 0.5 to 56 mm, 49 module 0.25 x 28 and 63 diametral from 1 to 112.
Longitudinal feeds totalled 63 and ran from 0.045 to 4.73 mm (0.0014" to 0.164") per revolution of the spindle with the cross-feed rates set to be twice as slow. As the lathes were so large, as part of the standard equipment the top slide (tool slide) was also equipped with power feed - over a length of 450 mm/17.5 inches - the 63 rates ranging from 0.022 to 2.3 mm (0.007 to 0.082").
Sealed against the ingress of dirt and swarf, the apron was fitted with a double clutch system to engage the power feeds, these being driven by their own shaft and disengaged longitudinally by one or more adjustable carriage stops fitted as part of the standard equipment.
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As an optional extra the carriage could be fitted with a rapid-feed mechanism powered by a motor flange-mounted on the right-hand face of the apron.  Leadscrews were of the conventional screwed type, 55 mm (2.1875") in diameter and grasped by double nuts. The carriage handwheel was equipped with a large-diameter micrometer dial, the gearing being set so as to provide an especially easy travel along the bed. Lubrication was automatic, two pumps lifting oil from a sump in the apron as the carriage moved, one distributing oil to the inside of the apron, the other directing a supply to the saddle and cross-slide ways.
Fitted with large a diameter micrometer dial, the cross slide was T-slotted to carry a rear toolpost; the top slide could be swivelled through 360° (and equipped, as mentioned, with a power feed) and both were fitted with taper gib strips. Saddle, cross and top slide ways were hand scraped "to assure a uniform film of oil".
Massively built, the tailstock could be fitted with a power drive to its spindle - though was otherwise equipped with a quite ordinary, manually-operated screw-driven type with its handwheel set at an angle. The whole heavy assembly was moved along the bed by crank-handle-operated, rack-and-pinion gearing; however, the manual drive could be supplemented, at extra cost, by an electric motor that gave a "rapid" feed.
Standard equipment provided with each new lathe was basic and consisted of: a complete electrical installation to suit the customer's voltage; coolant system; T-slotted combination faceplate and light-duty independent 4-jaw chuck; drive plate; longitudinal carriage stops; fixed steady; travelling steady; toolpost (type unspecified); two Morse centres (and probably a headstock spindle reduction sleeve); a selection of maintenance tools and an instruction and parts manual.
Optional extras were listed as the following - though it's hard to believe that others, such as dial-tread indicators, light units, different independent 4-jaw and tailstock chucks, etc. would not have been available: saddle and cross slide rapid-feed motor; crankshaft turning attachment; grinding attachment with bellows; convex and concave turning attachment designed for use with paper mill and types of large roller; rear toolpost; 3-jaw chucks and chuck backplates; taper-turning attachment; rotating 6-stop carriage stop; electrically-driven tailstock rapid travel; Dimotrol constant-speed cutting attachment; hydraulic copying; tailstock rotating centres; double (stacked) cross slide; digital read-out systems and what was listed, but not explained, as "automatic control" of the top slide..