safe edge. Mill files are used for smoothing lathe work
draw filing, and other fine, precision work. Mill files
are always single-cut.
FLAT files are general-purpose files and may be
either single- or double-cut. They are tapered in width
and thickness. HARD files, not shown, are somewhat
thicker than flat files. They taper slightly in thickness,
but their edges are parallel. The flat or hard files most
often used are the double-cut for rough work, and the
single-cut, smooth file for finish work.
SQUARE files are tapered on all four sides and
are used to enlarge rectangular-shaped holes and slots.
ROUND files serve the same purpose for round
Figure 5-25.--Hacksaws.
openings. Small round files are often called "rattail"
files.
length is the distance between the two pins that hold
The HALF-ROUND file is a general-purpose tool.
the blade in place.
The rounded side is used for curved surfaces and the
flat face on flat surfaces. When you file an inside
Hacksaw blades are made of high-grade tool steel,
curve, use a round or half-round file whose curve most
hardened and tempered. There are two types: the
nearly matches the curve of the work.
all-hard and the flexible. All-hard blades are hardened
throughout, whereas only the teeth of the flexible
blades are hardened. Hacksaw blades are about
Care of Files
one-half inch wide, have from 14 to 32 teeth per inch,
and are from 8 to 16 inches long. The blades have a
You should break in a new file carefully by using
hole at each end that hooks to a pin in the frame. All
it first on brass, bronze, or smooth cast iron. Just a few
hacksaw frames that hold the blades either parallel or
of the teeth will cut at first, so use a light pressure to
at right angles to the frame are provided with a
prevent tooth breakage. Do not break in a new file by
wingnut or screw to permit tightening or removing the
using it first on a narrow surface. Protect the file teeth
blade.
by hanging your files in a rack when they are not in
use, or by placing them in drawers with wooden
The SET in a saw refers to how much the teeth are
partitions. Your files should not be allowed to
pushed out in opposite directions from the sides of the
rust--keep them away from water and moisture.
b l a d e . The four different kinds of set are
Avoid getting the files oily. Oil causes a file to slide
ALTERNATE set, DOUBLE ALTERNATE set,
across the work and prevents fast, clean cutting. Files
RAKER set, and WAVE set. Three of these are shown
that you keep in your toolbox should be wrapped in
in figure 5-26.
paper or cloth to protect their teeth and prevent
The teeth in the alternate set are staggered, one to
damage to other tools.
the left and one to the right throughout the length of
the blade. On the double alternate set blade, two
HACKSAWS
Hacksaws are used to cut metal that is too heavy
for snips or bolt cutters. Thus, metal bar stock can be
cut readily with hacksaws.
There are two parts to a hacksaw: the frame and
the blade. Common hacksaws have either an
adjustable or solid frame (fig. 5-25). Most hacksaws
found in the Navy are of the adjustable frame type.
Adjustable frames can be made to hold blades from 8
to 16 inches long, while those with solid frames take
only the length blade for which they are made. This
Figure 5-26.--"Set" of hacksaw blade teeth.
5-16
