Named for the fact that the top of the headstock and tailstock were both formed into flat platforms to hold items such as micrometers and calipers, the Cincinnati "Tray Top" Cintilathe was manufactured by the Cincinnati Lathe & Tool Co. of 3207 Disney Avenue, Oakley, Cincinnati 9, Ohio in the United States of America.
Thought to have been introduced during 1933, during which year the Serial numbers were prefixed by the letter A, each year's production was allocated the next letter in the alphabet until 1952 when Z was reached. After that, as the decade was the 1950s, the digit 5 was added instead of a letter. At some point, probably in 1955, the lathe evolved into the somewhat more modern-looking Mk. 2, though the layout of the major controls and their functions remained unchanged.
Offered as four models, with swings of 10, 12.5, 15 and 18 inches, the "Tray Top" was a rugged machine and typical of American engine lathes intended for serious commercial use. Instead of simple increasing the centre height and offering the larger models for what other maker's euphemistically called lighter-duty work, the makers ensured that each version had its own bed casting and was suitable modified and specified so as to genuinely useful within its capacity range. In addition, a wide range of between-centres capacities was listed, from a minimum of 18 to a maximum of 60 inches at 6-inch intervals. The bed (sometimes found with a detachable gap), was carried on two heavy cast-iron plinths, each fitted with a lift-off door to provide access to the storage space, with between them (though at extra cost) a slide-out oil and chip pan.
Lubricated by splash from an oil sump, the all-geared headstock held flame-hardened gears and a spindle running in two Timken taper roller bearings on the 10 and 12.5-inch models but three on the larger types - the additional bearing being placed centrally to improve rigidity. The spindle nose, instead of being threaded, used the recently introduced American Long-nose Taper in an L00 size on the two smaller versions and an L0 on the larger - the arrangement providing a stiff mount, complete safety when run in reverse and reasonably quick mounting and dismounting of fittings.
Spindle bores were the same on each pair of smaller and larger pairs: 1.25" on the former and 0.5625" on the latter. All versions had a useful range of twelve spindle speeds driven by multi-V-belts from a rear-mounted motor and controlled by three concentrically-mounted levers on the headstock's front face. A modern touch was the use of a direct-reading speed dial that included coloured sectors for ease of setting. Speeds were available in two ranges: standard and high-speed; the former, on the 10 and 12.5-inch models spanned 30 to 1200 r.p.m. and 20 to 720 r.p.m. on the 15 and 18-inch. When equipped with the higher range (respectively on the smaller and larger pair of models, from 45 to 1800 r.p.m. and 30 to 1200 r.p.m.) more powerful motors were required (at extra cost) these being increased from the 1 h.p., 1.5 h.p., 2 h.p. and 3 h.p. found on the standard 10", 12.5", 15" lathes to, respectively, 1.5 h.p., 2 h.p. and 3 h.p. - with the 18-inch retaining its standard 3 h.p. unit. Available as an option was a combined multi-disc spindle clutch and brake assembly, a useful addition if the lathe was used for the production of short-run jobs  While the option of a spindle clutch allowed the motor to be left running, normal control was by electrical stop and start using a lever pivoting from (and of course moving with) the right-hand face of the apron, the motion being transmitted by a shaft the left-hand end of which was connected to the switchgear. On some models push-button controls - forward, reverse and stop - were fitted to the front face of the headstock with the addition, when specified, of a "jog" or "inching" control by which means large and heavy jobs could be turned a little at a time for inspection or setting. For safety, on long-bed lathes the saddle-mounted lever was duplicated by one just outboard of the screwcutting gearbox. Electrical equipment, which included switches for a spindle jog (inching) control, was safely enclosed within the headstock-end support plinth with an electrical master switch fitted on the left-hand face.
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Screwcutting was by an oil-bath lubricated, totally enclosed quick-change gearbox (so preventing the ingress of swarf, dirt and malicious objects) with both inch and metric pitches available, though the latter did require the mounting of two additional gears and the repositioning of three parts ….). Instead of the leadscrew reverse being built, conventionally, into the changewheel drive, on the Tray Top it was incorporated into the screwcutting gearbox. Each lathe not only had a leadscrew sized correctly in diameter and pitch  for its capacity (1" by 8 t.p.i. on the 10-inch; 1.125" by 8 t.p.i. on the 12.5-inch; 1.25" by 6 t.p.i. on the 15-inch and 1.375" by 8 t.p.i. on the 18-inch) but also an appropriate range of pitches and sliding and surfacing feeds. The 10-inch and 12.5-inch shared a range of 48 threads from 3 to 184 t.p.i.  while the 15 and 18-inch versions had 48 pitches available from 1.5 to 92 t.p.i. Sliding feeds on all versions ranged from 0.0019 to 0.125" per turn of the spindle and cross-feed rates from 0.0005 to 0.0308" on the two smaller lathes and from 0.009 to 0.0578" on the larger.
As might be expected, the apron was doubled walled with an oil bath in its base from where lubricant was directed, by a hand-operated plunger pump, both to the internal workings and also to the bed and cross-slide ways. Instead of a separate power shaft to drive the sliding and surfacing feeds, the Tray Top lathe used a slotted leadscrew with drive passed to the power-feed mechanism by the usual key-driven worm-and-wheel gearings - the mechanism being more like that usually found on lighter lathes such as South Bend. Individual selection and engagement levers were provided for the long and cross feeds, these working on the over-centre cam principle with an adjustment of the spring pressure available to obtain the best compromise between lever load and secure locking. The drive was protected from damage by over-enthusiastic use by a clutch built into the output shaft of the screwcutting gearbox where it joined, through a pair of gears, the leadscrew.
Of conventional design the compound slide-rest assembly had tapered grip strips with adjuster screws at both ends (requiring careful attention to adjust correctly). Cross slide travel was a generous 8 inches on the two smaller lathes and 10.5 inches on the larger; the top slide had 2.5 inches of travel on the 10 and 12.5-inch lathes and  3.375 inches on the 15 and 18-inch models. Hinting that the lathe had been designed by an experienced user, the top slide feed screw had a 1 : 1 step-up gear drive, the resultant increase in height of the handle permitting the use of an especially large zeroing micrometer dial that allowed the assembly to be rotated through 360°.
Tailstocks were sized for each model: the spindle travels and Morse-taper sockets being, in order: 3" and No. 2 Morse; 4.5" and No. 3 Morse; 6.25" and No. 3 Morse and 6.5" and No. 4 Morse. The upper body of each could be set over for the turning of slight tapers and the spindle locked by a heafty split barrel assembly that lay in traverse across the top of the casting.
Net weights of the shortest bed examples were, in order of size: 1439 lbs; 1510 lbs; 1998 lbs and 2118 lbs with each extra 6 inches adding 25 lbs, 30 lbs, 40 lbs and 50 lbs.
Supplied as standard with each new lathe was an inch screwcutting thread-dial indicator, a "dry" chip pan, a headstock centre step-down bush and two Morse taper centres,  a pair of large and small faceplates, a steady rest, a complete electrical and motor installation and the necessary wrenches. On the list of options were coolant equipment, an oil and chip pan, a taper-turning unit, metric threading changewheels, 3 and 4 jaw chucks, collets, an oversize steady resy, a micrometer carriage stop, a depth