While not his first invention, the hammer – and, in particular, the hammer head – has helped man expand his universe like no other invention until the advent of the personal computer. Through the centuries the hammer head has kept up with the times, evolving from the Stone Age to the Bronze Age to the Iron Age and through the Industrial Revolution (the Steel Age) to encompass materials such as stainless steels, tool steels and nonferrous alloys. Without heat treating, however, today’s hammer head would be no more useful as a tool than the ones whose heads were made of stone.

 

Scissors come in all shapes and sizes and are used for applications as simple as cutting paper and as challenging as cutting Kevlar – and for everything in between.

Consider the humble paper clip, whose utility highly depends on the properties of the metal developed by heat treatment. It may just be a thin piece of steel wire traditionally bent into a double-oval shape, but no one has invented a better method of holding loose sheets of paper together over the past century. In effect, a paper clip consists of two metal surfaces that are pressed against one another by the elasticity of the metal wire from which the paper clip is made.