Screwdriver: a Flat Blade Forged, Packed at a Low Heat and Tempered Grey (Holford, 1907)

A flat screwdriver is a steel shank flattened to a blade that fits the slot of a screw. H. Holford's 20th Century Toolsmith and Steelworker (1907) says most smiths make them so they twist or break on a hard screw, and gives his cure: forge it from 75-point carbon steel, strike the blade a few good blows on each flat at a low heat, harden it and let the temper run to grey. His Fig. 60 shows the shape without its handle. He gives no sizes and no handle, which are unknown here; the brine bath is from his chapter on the hardening bath. Source: H. Holford (1907), pp. 21, 118. Picture: his Fig. 60.