All surfaces are rough. The world of the engineer is made of solids whose surfaces acquire
their texture as the result of a great variety of processes. In some cases it is merely a byproduct
of forming the bulk shape, for example, in casting, molding, or cutting. More often a separate process affecting only the surface layers is applied after the part has been formed to its bulk dimensions. Some treatments remove material, as in grinding and etching. Others,such as plating, flame spraying, and sputtering, add it. ...