Manuals are available Lees-Bradner Machine Tools
Lees Bradner was formed in 1906 by a partnership Ernest J. Lees (1879--1937) and Hosea Townsend Bradner (1872-1963). The new company's intention was to exploit Mr Lees patents and experience with gear hobbing machines and so design a smaller model aimed at the rapidly expanding automotive industry and their need for compact transmission gearboxes..
By 1907 the No.5 gear generator was in production, a machine that could produce spur, spiral and worm gears. An important problem to be solved concerned what happened when gears were hardened - like all steel components they distorted. To solve this, the gears had to be ground and, seeking further sales and profits, the company put on the market first the No.10 gear-tooth grinder, followed by further models in both larger and smaller sizes.
While, of course, a thread can be cut in a lathe, this is a relatively slow process and requires a skilled operator; when mass production of threaded shafts is called for, a faster method is required - and one that can be set up to produce items of consistent accuracy. Hence, the introduction of the thread hobber, a machine that used very accurate, gear-like hobbing cutters. The accuracy lay in the cutter, not the skill of the operator and the accuracy of a lathe tool. By the late 1930s the system was well found and, during WW2, Lees-Bradner are reported to have made perhaps half the thread hobbers used by the Allied nations..