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Manufactured by Hobart Bros. of Troy, Ohio, U.S.A., this 3.93 inch centre height lathe admitted around 20 inches between centres and was intended as special-purpose machine to turn the copper commutators from electric generators and motors - and possibly for coil winding as well. The possibility of a coil-winding function is partially confirmed by the lathe's slow-speed drive (also necessary to avoid breaking the mica separators) and the red paint finish - a colour widely used for accessories employed in US automotive repair shops. Hobart are still in business (2011) manufacturing mostly electrical items such as welders and kitchen aid appliances - although the company is now owned by a large Corporation.
Heavily built for its relatively light-duty work - it weighed 171 lbs - it is likely to have been manufactured from the 1920s to the late 1940s and was of simple construction, with a small gap in the flat-topped bed and a hand-driven carriage connected to the leadscrew by a "fixed nut" with a handle at the tailstock end. Only a simple cross slide (with 2.69" of travel and a T-slot to mount a toolpost) was provided, with no way of mounting a swivelling top slide. To reduce the spindle speed, a drive shaft was arranged to pass over the headstock (it was carried in plain-bushed bosses above each bearing) with its end carrying a small gear that meshed with a larger one on the headstock spindle. Although the base unit and motor support are now painted grey, underneath is the same original maker's red paint finish present on the lathe together with a Hobart Bros. name tag - conclusively demonstrating that both units do indeed (as the design of the headstock casting would also confirm) belong together.
Drive came from a special motor contemporary to those times - a 1-phase, 1.5 h.p. 3500 r.p.m. repulsion-start type with a commutator and a matching flat-radial 4-brush set-up on the end plate. By rotating the plate (a ball-tipped lever was provided to move it) the motor's speed could be altered or reversed . In reality these motors were really only partially variable-speed, the torque dropping off badly at lower r.p.m. In order to provide a reliable, industrial-standard drive, the lathe was mounted on a massive cast-iron combined baseplate-cum-motor-mount
Missing from the lathe illustrated below is the essential "mica under-cutter", a device used to cut back the mica separator plates between the copper segments and also to clean up the slot edges and clear out any chips that might otherwise have caused a short circuit..
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