Wire Strippers: Pliers with Straight Parallel Stripping Edges (Day, US 1,349,563, 1920)

Pliers whose jaws stop with their two straight stripping edges exactly one wire-core apart. Grip the wire anywhere along the edges and twist: the insulation is cut through all round, but the copper is never nicked. A screw stop between the handles sets the gap for larger wire, and cutting edges beside the stripping edges cut the wire through. Result: wire strippers that strip insulation without damaging the conductor. Source: C. T. Day, US 1,349,563 (1920). Unknown: the metal, sizes and hardening. Picture: the patent drawing.