This section is from the book "Spons' Mechanics' Own Book: A Manual For Handicraftsmen And Amateurs", by Edward Spon. Also available from Amazon: Spons' Mechanics' Own Book.
A file is a steel instrument having the surface covered with sharp-edged furrows or teeth, used for abrading or smoothing substances, chiefly wood and metals. A file proper differs from a rasp, in having the furrows made by straight cuts (produced by a chisel or a sand blast), either single or crossed, while the rasp has coarse single teeth raised by the pyramidal end of a triangular punch. The effective power of the file resembles that of the saw, represented by a wedge not encumber d by the friction of one of the faces. The angle of the faces of the wedge is formed by the direction of the applied power and a tangent to the teeth. The diagonal position of the furrows of the file gives an additional shearing wedge power.
Examples of the cutting faces of files and rasps 12 in. long are shown in the annexed illustrations; the cuts of longer and shorter sizes vary in proportion. Figs. 330-335 are float cut; Figs. 324-329, double cut; and Figs. 336-341, rasp cut. Fig. 324 is rough; 325, middle; 326, bastard; 327, second cut; 328, smooth; 329, dead smooth; 330, rough; 331, middle; 332, bastard; 333, smooth; 334, dead smooth; 335, new cut; 336, horse; 337, rough; 33S, middle; 339, bastard; 340, second cut; 341, smooth.
New Cut. Middle
In using a file care should be taken that it is applied evenly to the work, or there is a danger of wearing it away rapidly in one spot. When a file loses its cutting power it may be resharpened.