|
Manufactured in the early 1980s by Little Gem Models of Unit 14/15 Central Works Site, Corby Workshops, Corby, Northamptonshire the "Little Gem Major" round-bed lathe, had a centre height of 5 inches, an overall length of 48 inches and a weight of 280 lbs. It was available as either a finished machine (to various specifications) or, at a saving in cost, as a kit of parts for home machining and assembly. The design aimed to give the model engineer and home-shop machinist a lathe that, while as versatile, adaptable and as rigid as possible, was reasonably priced and capable of further expansion as funds permitted. The basis of the machine was a precision-ground tube that carried a "novel wedge sliding key" to align the carriage and tailstock with the headstock; whether this arrangement was similar in principle to that used very successfully on the Metalmaster lathe, is not known but, if it was, then the accuracy of the alignment - always a problem with round bed lathes - would have been assured.
Cast in iron and fitted with plain bronze bushes, the headstock held a hardened and ground 1-inch bore spindle with either a 13/8" x 8 t.p.i nose thread or a simple integral flange to which could be bolted a chuck or faceplate. The 3-step V-belt pulley carried a ring of 60 indexing holes in the face of its largest diameter and was fitted - like a Myford ML7 - with a ball-bearing race to absorb spindle end thrust. An example of the lathe has also been found with a Poly-V-drive belt to the headstock, but it's not known if this was a later option by the maker or a modification by an owner
The lathe could be supplied with either a direct-drive headstock - with a speed range from 350 to 1100 rpm - or in a version that included an epicyclic gearbox built into the headstock pulley (exactly like those fitted to the American Craftsman AA109 lathes) and similar to the third-party accessories made in 1912- 1915 for the English round-bed Drummond by George Gentry and A. E. Bowyer-Lowe. With the epicyclic gearing fitted, the speed range became a much more useful 34 to 1100 r.p.m. Should the lathe have been ordered with the cheaper, direct-drive headstock, and the owner later wanted to fit the gearing system, a kit containing the necessary castings and gears was available - though this did need some final machining that could be accomplished on the lathe itself.
At 16" x 5.5", the cross slide was, for a small lathe, enormously long and designed - with its incredible 12.5 inches of travel - to allow the owner the chance of really successful milling operations when fitted with a vertical milling slide. 3 T slots were normally provided, although the option was offered of a matrix of tapped holes - or even a plain slide if so desired. At 7.5" x 4.25" the top slide was also generously proportioned and designed, with its two T slots and 5 inches of travel, to be fastened to an (optional) angle plate and mounted on the cross slide as an economical milling slide. As standard, the carriage was not driven through screwcutting changewheels - though a quadrant to carry screwcutting gears could be had at extra cost - but by a 8 t.p.i leadscrew (which ran down the middle of the bed and was carried in ball races at each end) connected to the spindle via a worm-and-wheel arrangement. At the tailstock end, the leadscrew was fitted with a very large micrometer dial that allowed a very precise hand feed to be made. Unfortunately, the only picture available to the writer is of the changewheel drive so, if you have a GEM lathe with the other system, I'd love to hear from you.
As the leadscrew had a full nut, a dog clutch was provided, this being of a most strange pattern, having six-slot engagement arrangement.
Fitted as standard with a rack-feed mechanism, the tailstock was also available, at no extra cost, fitted with screw feed; the spindle was 1.25 inches in diameter, had a very useful 5 inches of travel and carried a No. 2 Morse taper socket.
A simple swinging-arm countershaft was fitted, complete with a motor-mounting plate to take the recommended 0.75 hp 1425 r.p.m. motor; although a 3-step V-pulley was fitted, neither belt nor changewheel guards were fitted as standard - but could be supplied at extra cost.
Also used in the past by various lathe manufacturers, the "Gem" name is known to have been chosen by the Fitchburg Machine Works, of Fitchburg, Massachusetts; by Seneca Falls of New York (for earlier, popular but simple, 3-inch centre height by 19 inches between centres treadle-powered plain-turning lathe introduced in 1889); the Swiss watchmaker's "Gem Glorious", the Australian Gem, and models from the British lathe makers Tyne and Holmes.
If you have a Little Gem lathe the writer would be pleased to hear from you..
|
|
