Utility Knife: Strip-Made Blades and a Moulded Handle

Utility knife blades are made from a coil of carbon steel strip. A punch press punches the notches along it, the strip is scored across where each blade will break off, and it is coiled again and hardened and tempered, in a vacuum furnace or in line, typically to about 58 Rockwell C. The hard strip is then ground, honed and stropped along one edge, and snapped at each score line into trapezoid blades. Snap-off blades use the same idea: the break comes at the score lines, where the metal is thinnest. The handle that holds the replaceable blade is die-cast metal or moulded plastic.