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Holbrook C8 Electronic Lathe Photographs
Holbrook B No. 8 Precision Lathe Home Page

Save for the headstock and drive system, the Holbrook C8 Electronic was identical to the Model B No. 8 precision lathe -this being fitted with an all-belt drive system with either a fast-and-loose, two-speed, ball-bearing, wall-mounted countershaft unit with a foot-operated belt shifter - or much the same assembly held on wooden board supported by cast-iron uprights bolted to the back of the stand. However, to improve the drive system, in the early 1940s a version of the lathe was listed as the Type C8 Electronic, this having an enclosed, backgeared headstock and variable-speed drive - with the rotary speed dial, push-button starter and rev counter mounted in a housing carried on a post fastened to stand towards its tailstock end. The variable-speed drive - of some complexity and great cost - used a massive B.T.H. 2 h.p.  250v DC motor that drove, using twin V-belts, direct to the spindle pulley. Control was by an early electronic drive system that used a thyratron system, again by BTH, originally held in a large sheet-steel cabinet bolted to the headstock end of the lathe's cast-iron cabinet stand. In some respects the drive would have been similar to that developed by "Ward-Leonard" (used on some Cromwell lathes) and that fitted to the American Monarch 10EE. The result was a step-less speed range, with dynamic braking, from 20 to a remarkable 5000 r.p.m. The C8 is known to have run with uncanny smoothness, a coin balanced on its edge on the headstock of a new lathe being perfectly stable even at maximum r.p.m.
4' 6 " long (1320 mm) and 1' 5" (432 mm) wide, the early lathes weighed approximately 440 lbs. and were supplied, as standard, with an 8" diameter T-slotted faceplate; fixed and travelling steadies and a hand Tee rest. Although no chucks were included with the ordinary equipment, nine collets from 1/8" to 5/8" were - and are often found held in a neat rotating circular holder (made from oak) together with the draw bar and the necessary headstock spindle-adapter sleeve. As the C8 was so expensive, it is believed that only around ninety examples were built, a number of which are known to survive..

High-resolution pictures - may take time to open

Early speed-control panel and rev counter

Late speed-control panel
and rev counter