Files and File-Making

The common file, as every workman knows, is an Implement, the flat or curved surfaces of which are notched or serrated in such a manner that, on being rubbed on the wood, ivory, metal, or other hard substance for which the tool is intended, a surface of more or less smoothness is obtained.

Files are made of bars of steel prepared in a peculiar manner, it being necessary that the file should be formed of the hardest possible metal, or else its working surface would be speedily worn away. The steel is therefore rendered harder than usual by means of a process known as double conversion, the metal thus prepared being said to be doubly converted.