The general difference is only the thickness of the grinding wheel, which is called "mesh". As for what metal to grind, there is little difference. Diamonds are often used to dress grinding wheels, but there are other kinds. For example, the grinding wheel used for hand sharpening is not diamond, but a thin disk made of wear-resistant steel. The center of copper is a diamond. Just take a closer look. Copper is actually called copper. Don't call it that, people will laugh at you for being unprofessional. Copper: copper, brass, bronze.