Jen-Son Lathe Page 2>
Although the background to the unusual backgeared and screwcutting "Jen-son" is unknown, it could, with its flat-topped bed with angled edges (and other design clues) have been English in origin - or Australian. Often written "Jenson" in error, the lathe had a headstock headstock pulley intended to take a V-belt drive and a spindle running in roller bearings - one headstock carries a badge proclaiming "Roller Bearings BELT Endless V Self Adjusting" - the lathe looks to have manufactured during the 1930s, though its general design may well have come from a decade earlier. Whether it was built into the 1940s is not known for, as yet, no surviving publicity literature has been found. Oddly, for a relatively simple and light lathe, it was very well constructed, with an excellent finish on turned parts and incorporated a number of novel features. It could also be had in several forms, from a simple arrangement for use by amateurs to one fully equipped for production work. In its latter form, it came mounted a box-like cast-iron stand complete with six wooden storage drawers and a motorised countershaft-cum-drive assembly bolted to its left-hand face; engagement and disengagement of the drive was by a foot-pedal operated control. Another option was drive by a foot treadle through a crank arm on the inside of the headstock-end plinth to a heavy, 3-step flywheel carried on the plinth's outer face. Of simple and economical design, the motorised countershaft used a single, central plain bearing with drive and driven pulleys overhung on opposite sides, that from the motor being a 2-step - the system giving (including the use of backgear) a range of 16 speeds would have spanned approximately 25 to 800 r.p.m. A headstock lever-operated collet closer was fitted (the unit was carried on a bracket secured with bolts to the top of each spindle bearing housing) together with specially constructed tailstock carrying an indexing capstan unit. One example has also been found with a chain-driven, front-mounted drive shaft to provide power cross feed. The shaft passed through a boss beneath the carriage handwheel, the latter having a centrally-mounted knurled-edged knob that rotated to engage and disengage the drive.Jen-Son Lathe Page 2>
The bed, its chip tray, feet and the headstock were cast as one - with the headstock somewhat cantilevered out and carrying a 4-step drive pulley. Drive was either by the previously-mentioned stand-mounted countershaft or by the same unit but mounted remotely, though this too was presumably intended to fit below the lathe as the makers fitting a wide jockey pulley at the front of the bed in order to stop the belt rubbing on the casting.
Drive to the carriage was by changewheels (through a lever-operated mechanism that incorporated a dog clutch), to a shaft that ran down the back of the bed. From there, at the tailstock end, it was transferred by a gear train to a leadscrew that ran down the bed's centre line - the early Drummond 3.5-inch flat-bed lathe having its leadscrew in the same position. One some examples of the jen-Son discovered, the tailstock-end gear train was guarded, on others left open with no brackets or tapped holes to show that one could have been fitted.
Interestingly, the screwcutting chart was marked with columns that suggested changes of pitch could be obtained by altering the gearing at the right-hand end, while the provision of a short banjo arm at this point would seem to offer confirmation - even though it's something of a mystery as to how this bracket carried the gears. This convoluted system (though not the use of changewheels at the "wrong" end) was often used on early full-sized lathes when power-cross feed was required (and some smaller ones until the 1930s, for example, the English Pools Major with a sliding worm wheel being mounted on the drive shaft and the other necessary gearing fitted to the back of the carriage).
Arranged conventionally with a leadscrew clasp-nuts in conjunction with a rack-and-pinion drive for hand operation, the carriage carried a handwheel of distinctive design with finger cut-outs in the periphery and a cast-in radial bar, machined with knurled finger grips, that extended beyond the rim. The compound slide-rest used a short cross-slide with a long (but not long enough) cast extension at the rear to protect the feed-screw from swarf. In order to provide a long enough travel, the cross-slide ways were extended well forwards but, with the slide in any normal working position, the front of the feed-screw was left exposed. Unusually for a small lathe of this era, the cross-feed micrometer dial was large and clearly engraved.
If any reader has a Jen-son lathe the writer would be interested to hear from you.
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