This page has been validated.
ON
PLANE METALLIC SURFACES,
OR
TRUE PLANES.
The method hitherto adopted[1] 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.[2] The process of grinding is,
- ↑ That is, prior to the year 1840.
- ↑ Surface plates consist (as is well known to those familiar with our workshops) of iron plates, strengthened by ribs on their backs, and having their faces as smooth and as true as possible. They are used for the purpose of testing and correcting any surfaces which are required to be made true. A straight edge is also used for testing the truth of surfaces; it is generally so called when its surface is very narrow as compared with its length, being usually the side face of a long flat bar. Surface plates are made of various sizes.
A simple and interesting experiment may be tried with a
B 2
