File Filosophy
Being some Hints regarding the proper Methods of using Files and the various Applications of the most common Files

FILE FILOSOPHY width does not exceed one-eighth the length or stroke of the file. To the uninitiated this would seem to require that the file should have a perfectly true and straight surface, but were it practicable to make the file abso- lutely flat and true, it would then be necessary to move it in absolutely straight lines across the work; even were this operation possible, the pressure, if applied to each end of the file, as is the usual custom, would give it sufficient spring to cause a slight concavity to its cutting surface, and thus an inevitable rounding to the surface of the work must be produced. Therefore, to produce a flat surface under this severe test, or even under more favorable circumstances, the file should have a convexity given to its surface. Convexity in Files Undoubtedly, few, even of the old filers, have given the subject of convexity as it bears upon broad surface filing the thought it is entitled to. It is known to many mechanics that a file which will bite and cling, with the accustomed downward pressure, upon wrought iron or soft steel will require a greater pressure to prevent it from glazing or slipping over the work, when applied to broad cast iron surfaces. This is owing to the glassy nature and extremely granular formation of these surfaces; consequently the teeth should enter the surface deeper than in the more fibrous metals or they will soon glaze over and become dulled or shiny, thus giving to the file the appearance of being soft, while the contrary may be the fact. Many a well hardened file NICHOLSON FILE CO, 13