There should be no pressure on the file as
it is being drawn back. The teeth slant
forward and back stroke pressure will
cause them to break more readily than on
the forward stroke. However, when filing
very soft metal such as aluminum, a slight
back stroke pressure will aid in cleaning
Using a new file. When a new file will be used,
observe the following precautions:
Never use a new file to remove the fins
and scales on cast iron.
Do not use a new file on a narrow surface
such as sheet metal, because the narrow
edge of the metal is likely to break off the
sharp points of the file teeth.
A new file should be broken in by using it
first on brass, bronze, or smooth iron.
After using a new file, the teeth will clog
up with metal filings which will scratch the
work. One way to prevent this condition is
to rub chalk between the teeth before
Crossfiling. Crossfiling means that the file is
moved across the surface of the work in an approximate
crosswise direction. This is shown in figure 4-76. To
use this method, proceed as follows:
Clamp the work securely in a vise so that
the area to be filed is horizontal and is parallel to and
projecting slightly above the vise jaws.
File with slow, full-length, steady strokes.
When an exceptionally flat surface is
required, hold the file at an angle and file across the
entire length of the stock. Then, turn the file as shown
in figure 4-77, and file across the entire length of the
stock again. Because the teeth of the file pass over the
stock in two directions, the high and low spots will be
readily visible after filing in both positions.
Continue filing in one position and then
the other until the surface has been filed flat.
Test the flatness with a straightedge or
with prussian blue and a surface plate.
Figure 4-76. Crossfiling
Figure 4-77. Filing for a Flat Surface
Drawfiling. Drawfiling produces a finer surface
finish and usually a flatter surface than crossfiling. See
figure 4-78 and proceed as follows:
Install small parts in a vise.
Hold the file as shown in figure 4-78. The
cutting stroke is away from the body when the file
handle is held in the right hand. If the handle is held in
the left hand, the cutting stroke will be toward the body.
Hold the file at right angles to the direction of
the stroke, and keep hands relatively close
together to prevent bending the file.
Keep the pressure light. The pressure
can remain the same for both the cutting stroke and the
return stroke. The speed of filing is not important.
When drawfiling no longer improves the
surface texture, wrap a piece of abrasive cloth, Federal
Specification P-C-451, around the file and stroke in the