Care. Observe the following practices for
the care and upkeep of hollow punches:
Clean punches with a clean rag
after each use.
Apply a light coat of oil before
Store punches so that the edges will
not be damaged.
4-11. Files. Files are hardened steel tools for cutting,
removing, smoothing, or polishing metal. The cutting
edges (or teeth) are made by diagonal rows of chisel
cuts. The parts of a file are shown in figure 4-65.
Types. Files can be classified by grade and
Grade. Files are graded according to
whether they have single or double-cut teeth, and the
degree of fineness.
Single and double-cut teeth. The
difference between single and double-cut teeth is
apparent in figure 4-66.
Single-cut. Single-cut files have
rows of teeth cut parallel to each other. These teeth are
set at an angle of about 65 degrees from the centerline.
These files are used for sharpening tools, finish filing,
and draw filing. They are also the best tools for
smoothing the edges of sheet metal.
Double-cut. Double-cut files
have crossed rows of teeth. The double cut forms teeth
that are diamond-shaped and fast cutting. These files
are used for quick removal of metal, and for rough work.
Degree of Fineness. Files are also
graded according to the spacing and size of their teeth,
or their coarseness and fineness. Shown in figure 4-67,
the usual grades of fineness are called bastard, second
cut, smooth, and dead smooth. The fineness or
coarseness is influenced by the length of the file.
Shape. Files come in different shapes.
When selecting a file for a job, the shape of the finished
work must be considered. The more common file
shapes are described in the following paragraphs.
Triangular files. Triangular files are
tapered toward the point on all three sides, as shown in
Figure 4-65. File Nomenclature
Figure 4-66. Single-and Double-Cut File Teeth
Figure 4-67. File Teeth Spacing and Fineness