Device for Corrugating Strips
Having a sheet-metal cog rail to make for the adjusting mechanism of an enlarging screen, I built a cog-forming device as shown in the sketch. A block of wood served as the case and two levers with hinges were fixed to one end of it. Two pieces of hardwood were grooved at their ends as shown in the smaller sketch, to fit over three tenpenny nails, A, held in place on the block by staples. Four small nails, B, were set into the block, as shown, to act as guides for the strip of metal, which was fed between the forming blocks and the nails on the case. By pressing down on the hinge levers, the strip was formed into corrugations or teeth. In order to make the teeth uniform it was necessary to guide the forming pieces by having one of the cogs fit over the first nail. The strip thus formed was fixed to a wooden piece and served as a cog rail.—R. E. Henderson, Walla Walla, Washington.