These blacksmiths were not metallurgists or steel experts in the modern sense, yet they obtained very good results. When they discovered a good thing, they treasured it and passed it on to their sons. In this way, the art of working steel progressively was improved. When the Machine Age came along and such things could be done quickly, it became the custom to make steel parts with highly polished surfaces. And out of this grew a theory that a part which had been highly finished would give much better service than one with a rough surface. Indeed, a highly finished surface became a symbol of superior quality. A few years ago, our Research Laboratories received a simple, flat spring, that was nicely polished, but was giving trouble. In fact, it would break regularly when flexed only about 2,000 times. So we were asked to design a new spring to fit into the very limited space where it would have to work. In a similar problem we had done some experimenting, and had developed a treatment for increasing the life of such parts. It consisted of bombarding or hammering the surface with thousands of little steel shot. In that way we simply substituted thousands of such little blows for the blacksmith's hammer. But in this process, we lost the mirror finish. |