Page:Miscellaneous Papers on Mechanical Subjects.djvu/11



method hitherto adopted in getting up plane surfaces has been (after filing to the straight edge) to grind them together, with emery. In some cases it has been customary to try them previously on a surface plate, and to go over them with the scraping instrument; but they have always been ground afterwards. The surface plate itself has been invariably treated in the same manner. The process of grinding is, Rh