Razor Blades from a Continuous Steel Strip (Tarbox 1915)

Safety razor blades are made without ever cutting the steel into loose pieces first. A long strip, blade-wide and blade-thick, is punched and notched at every blade length. It then runs through grinding, hardening, tempering, edge grinding, stropping and wrapping, and only at the end is it snapped apart into blades. John Tarbox's machine even set the temper itself, with a selenium cell that watched the colour of the steel. Source: J. P. Tarbox, US 1,165,037 (1915). The patent gives no temperatures, steel grade or blade sizes. Picture: Tarbox's drawing of the whole line.