Manufactured in France by Ets Jenny & Co. of 49, Rue Fabre-d'Eglantine, 49, Fontenay-sous-Bois (Seine) to the East of Paris, the Jenny is one of only three makes of plain-turning, "bench precision" lathe so far known to have been manufactured in France - the others, also Paris based, being the S.O.M.B.V. and ARE.
With a 91 mm centre height and either 100 or 400 mm between centres, the Jenny was of the traditional plain-turning "bench precision" type, a simple but beautifully-made class of lathe that was, at one time, an important part of both ordinary toolrooms and those shops that dealt with the manufacture, repair and maintenance of instruments, clocks, watches and other finely-made mechanical parts. Like other European and American makers of similar high-class machines (of whom there were many including, amongst the better-known, Schaublin, Boley, Lorch, Mikron, Wolf,Jahn, Ames, Cataract, Pratt & Whitney, Stark and Hardinge) the Jenny could be arranged to perform in the usual three distinct roles common to the type: toolmaker, second-operation and production capstan. The toolmaker's type, intended for one-off precision jobs by a skilled turner, was equipped with a screw-feed compound slide and tailstock while the second-operation version (sometimes called a "finishing lathe") had a choice of screw or quick-action lever-operated slides with the production model fitted with a bed-mounted 6-station capstan unit and a lever or screw-operated cut-off slide. By the simple means of changing the fittings bolted to the bed, each version could be assembled in a matter of minutes and pressed into service with a minimum loss of time.
Although early bench precision lathes always had some form of remote or complex stand-mounted countershaft drive system, by the 1930s these had become much neater and either an integral part of an underdrive stand or arranged as a compact unit behind the headstock - a good example being that by the Swiss maker Simonet. Others, in order to suit a wide variety of different tasks, came with more highly developed systems that incorporated clutches and brakes - as used for example on the Schaublin 102. Simple, neatly designed and well-guarded, the drive on the Jenny had the motor mounted on the back of the stand and driving up to a particularly robust countershaft bolted in place behind the headstock. It is believed that both bronze and taper-roller bearing were used in the headstock, the spindle in both cases having a 16 mm bore and a threaded spindle nose formed to take direct-fitting, lever-action closed collets. Drive to the spindle was by a smooth-running flat belt passing over a choice of either 3 or 4-step cone pulleys. Two spindle-drive motors were offered: a single-speed 1.3 h.p. or a 2-speed 2/2.5 h.p.; these, in conjunction with either a single or 2-step pulley on the motor to countershaft drive, gave 6, 8, 12 or 16 speeds that spanned a range from 170 to 2750 r.p.m. Unusually, two additional countershafts were offered, both almost certainly of unique design with each having its pulley shaft extended to a bearing support bracket at the tailstock end of the bed. Type 2 was fitted with a long jockey pulley behind the headstock to tension the drive belt and, able to be slid up and down the shaft and locked to it where required, was a pulley intended to take a round belt that connected to an "overhead" from which toolpost mounted high-speed grinding and milling spindles could be driven. The "overhead", with two sets of jockey pulleys to guide the belt through two right-angles, was adjustable up and down the length of a bar set horizontally behind the bed. The Type 3 countershaft was similar but lacked the headstock belt jockey pulley; at the tailstock end was a large diameter flat pulley used to power, via a tensioning jockey pulley, a choice of two special drilling attachments that mounted in place of the tailstock. Both units included a bracket to carry a pilot-guide bush and were intended for the use of both normal (up to 16 mm diameter) as well as very small diameter drills. With small drills, in order to obtain the very high speeds required, the part was mounted in a spindle chuck and spun forwards while the drill unit had its belt twisted to reverse the drive - the result being at least a doubling of the effective speed. One drill unit was heavily built with a single lever to advance the spindle, the other rather lighter with a capstan handwheel working through rack-and-pinion gearing.
A variety of slide rests was offered including a standard compound slide assembly with all-screw feed (for this class of lathe the top slide travel looked to be on the short side, though the ways and feed screw were fully covered); a compound assembly with a screw-feed driven cross motion but lever action on the top slide; a crew-feed compound slide rest assembly fitted with a cross slide having a section machined to hold a rear toolpost; a crew-feed cut-off slide with a quick-action, 2-start thread on the feed screw; a lever-action cut-off slide with rack-and-pinion drive; an all-lever-action compound slide assembly with, on the cross slide, a rear toolpost for parting off and a heavy-duty production compound slide rest assembly with all-lever feeds - each slide being fitted with a neat, rotating multi-depth stop and the cross slide machined to take a rear toolpost. Also on the list of option was a special tailstock with a 5-station capstan turret with rack-and-pinion drive to its spindle and a rotating multi-stop for length control.
Avez-vous un tour de Jenny? Si c'est le cas, l'auteur serait heureux de vous entendre.
Do you have a Jenny lathe? If so, the writer would be interested to hear from you..