Manufacturers of a wide range of machine tools - grinders, power presses, hacksaws, slotters, milling machines, shapers and a wide range of engineering accessories - the Machines & Tools Corporation of Lentin Chambers, Dalal Street, Mumbai, sold their products under the "Coronet" label. During the 1960s and 1970s the lathes they offered were in capstan and centre types, the former though to be licence-built copies of a German design, but the latter of their own conception, being backgeared, screwcutting and of conventional design and construction.
Offered in several versions (and what may have been early and late models) the neatly presented PLN-5 could be had as a 140 mm x 558 mm, 160 mm x 685 mm or 180 mm x 685 mm. All were of identical design and construction - but sized correctly to handle their work capacity with the beds having widths of, respectively|: 180 mm, 196 and 230 mm. Following a fashion that had died out by the 1960s, the V and flat-way bed had the front V constructed with a much wider outside surface set at a shallow angle (to better absorb wear) and a much narrower but steeper inner surface to take the tool thrust - a gap being offered as an option on all types.
Headstocks were also specific to the model and suitably beefed up on the larger sizes - the spindle bore of the smallest version being 25 mm (with 12 speeds) and 28 mm (with 16 speeds) on the two larger. Motors varied in power but were generally rather puny, being 0.75 h.p. on the two smaller models and 1 h.p. on the largest , all of which gave a speed range from approximately 45 to 1440 r.p.m. However, over the years the specification appears to have changed, with early versions all being restricted to just 8 speeds, though with the same range.
Fitted with a 2-step pulley, the 1 h.p. single-phase motor drove to a countershaft and from there to the spindle by an "A" section V-belt running over 4-step pulleys. Combined with backgears of the quite-running helical type (though these would have required improved thrust bearings to take the increased axial loads generated by the type) 16 speeds were available. Although no speed chart was fitted, it would be safe to assume that the range spanned something like 30 to 1500 r.p.m
Screwcutting and feeds were by the usual type of Norton quick-change gearbox with a sliding tumbler and two levers and drive from the headstock through changewheels and an internally-mounted tumble-reverse mechanism. Changewheels were guarded by a substantial cast-iron cover that fitted over two studs at the base and with a turn lock at the top. Power sliding and surfacing feeds were driven from a keyway in the leadscrew with engagement by a lever protruding from a gated slot in the apron's right-hand face. Usefully, a thread-dial indicator was fitted as part of the standard equipment being mounted, like those on early Harrison lathes, on a hinged bracket screwed to the apron's left-hand face. In addition to screwcutting, sliding and surfacing feeds were fitted, driven by a key running in the slotted leadscrew with the drive through the usual worm-and-wheel gearing. Instead of a lever to select the feeds and a clutch to engage them, on the Coronet both selection and engagement was by a single lever that protruded through the right hand wall of the apron.
Able to be set over on its base for the turning of slight tapers, the tailstock had a barrel locked by a proper split clamp and engraved with ruler lines - though as these lacked digits there was not way (apart from measuring and stamping the numbers oneself) what the spacing was supposed to be. The bed clamp was operated by a usefully long lever that users report to be particularly effective.
Although the engraving on micrometer dials and tailstock barrel could hardly be classed as world-beating, from the lathe's general appearance quality and attention to detail seems to have been respectable with a more-than-decent cosmetic finish and lots oiling points, those for the saddle being felt-filled holes covered by removable caps - a most unusual fitting on any machine tool. It is notable that all the ancillary equipment - chucks and motor, etc. - was Indian-made..