Adjustable Spanner: One-Piece Forging, Broached Guide and Worm

A 1938 patent for making adjustable wrenches lays the work out in order. The head, fixed jaw and handle are forged in one piece from properly alloyed high-carbon steel, the forging also forming the rectangular opening for the worm. The head is drilled to start the guideway for the movable jaw, and the guideway is then broached. Holes above and below the opening are drilled, and the lower one guides the tap that threads it for the worm's pin. The movable jaw's slide has a rack hobbed or machined on its back; it is slid into place, and the pin, with a rolled thread, is fitted with the knurled worm gear and a conical compression spring that takes up slack.