Along with knives, hammers and axes, the saw is a tool that has been used by humans for thousands of years. A toothed piece of metal fitted with a handle has been applied to cutting almost every material ever invented, from the softest wood to the hardest metals. In Britain, an industry to supply the nation's saw users began to grow rapidly in the eighteenth century, and marched with the Industrial Revolution to become the largest in the world. Millions of saws were made, and like most other tools, they were exported worldwide, but they don't survive very well, because their blades are thin,...