A technical student can make do with either a single or double toothed file. Sizes and shapes are fabricator’s choice. Files will typically be used for light metal work, removing burrs on metal projects or truing the cut end of a screw. Some technicians use aggressive rasp files in lieu of surform blades to smooth and shape A/B foam.
Files are versatile tools that can be used in a variety of different ways. Some examples are squaring workpiece edges, rounding corners, removing burrs, sharpening blades, and smoothing rough surfaces. A file can be specialized for a certain procedure depending on its shape, size, cut, and coarseness.
Files have a unidirectional cutting edge, meaning they cut in only one direction. The pressure applied with each stroke will dictate the amount of material removed and quality of finish. Dragging a file on the opposite stroke will dull the blade and shorten the life of your file. A wire brush is handy for cleaning the cutting blades for optimal cuts on each pass.
Tang — is the portion that the handle attaches to.
Heel — is the area just before the start of the teeth.
Face — is the section that actually cuts containing the teeth.
Edge — is the side of the file, this part may or may not have teeth.
Point — is the tip of the file, and it does not have to come to a point.
Length — is measured from the heel to the point.
A file can be identified by 3 characteristics: Cut, Coarseness, and Shape
Most files come in single or double cuts. A files’ cut dictates the amount of material that is removed and its coarseness determines the finish that it will leave.
Single: A single direction of teeth extending across the face along the length of the file.
Double: Two directions of teeth which crisscross. The first row is generally referred to as the "over-cut," and the second row as "up-cut". The up-cut is somewhat finer and not as deep as the over-cut. Will remove more material than a single direction file.
Specialty: A Vixen file (curved tooth) is an example of a specialty file that is designed for rapid removal of material and creates an exceptionally smooth finish on soft metals and wood.
The coarseness refers to the final finish left on the product. There are a variety of different coarseness' which ranges from "bastard" which is a very coarse file to a "smooth" file which produces a smooth finish.
Various different shapes and sizes of files allow the user to perform specialized tasks. Some of the more commonly used files in our field are:
Mill / Flat: almost exactly the same in shape. Mill is tapered slightly in width for about one-third of its length. The cut can be single or double and both edges can have teeth. These files are used for draw-filing and cross-filing
Round/Rat-tail: Are circular in cross section and may be either tapered or blunt and single or double cut. They are used principally for filing circular openings or concave surfaces.
Half-Round: Are files that cut on both the flat and round sides. They may be single or double cut. Their shape permits them to be used where other files couldn't.
The most common method of filing. The file travels across the material from point to heel, the return stroke should not touch the work because it does not remove material it only serves to dull the teeth. This is a common mistake in use of a file.
The file is drawn from edge to edge. this produces a finer finish because the teeth are drawn across metal in a way that produces a sheering effect.