Bursgreen Capstan Lathe
Made by the Burrows and Green at the works of the Bursgreen Company during WW2, this very interesting, specially-designed small capstan lathe was, it is believed, used for the production of incendiary ammunition. As the process must have involved some special procedures, the arrangement of the lathe was, in some ways, unique and., consequently, an initial attempt to patent it was made on July 17th 1941 under number 551,374. However, applied for by the designers, Mr Frederick Walton Burrows and Albert Green, it appears that the attempt was either unsuccessful or abandoned, the machine carrying a "Patent Applied For" badge. Titled "Improvements in and relating to Multiple Drilling and Like Machines", the gist of the application - drawings are at the bottom of the page - claimed that, as a conventional capstan lathe with a horizontal rotating head had its tool brought into operation by a "curved motion" followed by a straight-line feed, this could cause, especially with fine work, errors in alignment to the axis of the headstock. The Bursgreen unit, it was claimed, would overcome this problem by using a block, able to hold three tools set in a vertical line, that was arranged to move vertically and so bring each into use one after the other. At the base of the block, at the back was what was described as "roller" or "bowl". Behind the block was what the patent described as an "assembly", this being machined with three opening, each backed by a rising, inclined ramp. After a tool was fully withdrawn from its work, the "roller" or "bowl" entered the lowest opening in the rear assembly and ran up the inclined plane, so bringing the second tool into position. A locking mechanism, using a slot on the block and a spring-loaded catch, was provided to hold the new position. When the last operation had been completed, the block was lowered by releasing the spring catch and letting it fall. Longitudinal travel was set by the usual set of adjustable stop screws set in a rotating housing. The patent also described, rather casually, how the vertical movement of the block could be changed to horizontal or at an inclination: "suitable slight modifications being made accordingly in the return of the block to its starting position where its own weight is not available". Perhaps as a consequence of its special application, production of the lathe must have been limited and the example shown below is believed to be the only surviving example.Some pictures are high-resolution and may take time to load
The usual lever-operated cut-off or forming slide was fitted, this being equipped with a 4-position rotating stop, a front toolpost held in a T-slot and, at the rear, a set of ways machined with V-edges suitable for taking, presumably, some sort of adjustable slide rest.
If the drive arrangement has survived unmodified, the motor would have been mounted on an adjustable plate behind the headstock driving directly to the overhung pulley on the end of the spindle. As currently configured just two speeds are available, though when new perhaps the option existed of a 2 or even 3-speed 3-phase motor to give four or 6 speeds.
Appearing now to be somewhat modified - or possibly fitted with ancillary equipment when new - the Bursgreen currently has an unusual arrangement for a British-made production lathe, with a rotating head held in a vertical " revolver" position, just like those used for example on German Pittler production lathes.