Made by the Jackson-Rigby Company of Shalford, Surrey, established railway engineers who concentrated on parts for miniature steam locomotives, the "JR" lathe was originally badged as the "J.R.C." and may have resulted from the involvement of Mr. Henry Greenly (the well-known locomotive designer) who had a financial interest in the Company. Greenly is said to have made some improvements to the design, but the lathe cannot have been manufactured for long, probably only from 1922 until 1926 - the year Jackson-Rigby moved to New Romney in Kent where they undertook a contract to maintain the locomotives of the newly-formed Romney, Hythe, and Dymchurch Light Railway that Greenly was building for its owner, Cat. Howey - the track running a miniature "main-line" steam service from the Cinque Port of Hythe. More can be downloaded here, by Dale A. Bitsch, under the heading "The Romney Connection" about this fascinating undertaking and Greenly's other involvements with miniature steam engines.
Made in 3 and 4-inch centre heights (the example below is a 4-inch), and 12 inches between centres, the J.R. lathe was especially well built with considerable attention to detail and a fine cosmetic finish. Available for bench mounting (when a separate foot motor was offered) the makers also provided an unusual stand that resembled the one used on many EXE lathes. Overhung on the outer face of the headstock-end leg, the flywheel was turned by a foot pedal connected to a very heavy crank on the other side, drive to the headstock being by a round leather "gut" rope".
Cast as one with the headstock, the gap bed was of cantilever form that allowed the 60-degree edge ways to remain distortion free as the machine was bolted down - this being by the four closely spaced bolts under the headstock. Bored hollow, the headstock spindle ran in Hoyt "copper-hardened" split bearings closed down by slots positioned to the rear with a giant, 4-step cast-iron 'gut-drive' pulley between them. With no backgear fitted (nor any evidence that one could be mounted as an option) in order to obtain a reasonably slow bottom speed the largest of the headstock pulleys was made oversize and driven by an extra small pulley on the flywheel, this arrangement requiring the use of a belt that could have a section unclipped to shorten it.
Screwcutting was by fine-pitch changewheels retained by simple and quick-to-release wire spring clips fitted to grooves in the end of their mounting studs - a similar system being used on the popular American Senica Falls "Star" lathes. A three-slot bracket carried the changewheels, with the drive to the leadscrew passing through a simple dog clutch built into the leadscrew headstock-end support bracket. With two 20t gears in the train feeds as fine as 268 t.p.i could be achieved. The nut on the cast-with-apron was of the "full" type and thus the carriage could only be moved along the bed by either a power feed through the changewheels or by a handwheel on the end of the leadscrew - there was no quick-action rack feed. Surprisingly the leadscrew handwheel was fitted with a micrometer dial, as was the single tool slide, both being well finished with knurled edges and clear graduations.
A usefully large T-slotted boring table was fitted that carried a single, swivelling top slide fitted; the slide was retained by a single "T-bolt" - the round end of which could be screwed in or out to set the lock position for the short clamping bar--it being unnecessary to use a spanner to reposition the side on the table. An unusual option was available in the form of a tilting T-slotted table that pivoted on centres arranged at the back of the carriage with a screw thread at the front (running through trunnion nuts) that performed the necessary elevation.
For a small lathe the tailstock was very robust and carried a No. 1 Morse taper automatically ejected as the barrel reached the end of its travel.
If you can add anything to the Jackson Rigby story, or have a JR lathe, the writer would be pleased to hear from you..