the cutting action of the file and tends to clog the file
used to make positive identification of metals, but it can
teeth, it is SOFT. If the material offers considerable
be used to get a general idea of the type of metal being
resistance to the file but can be filed by repeated effort,
tested and to compare the hardness of various metals on
it is HARD and may or may not have been treated. If
hand. Thus, when identification of metals by other
the material can be removed only by extreme effort and
means is not possible, you can use a file to determine
in small quantities by the file teeth, it is VERY HARD
the relative hardness of various metals. The results of
and has probably been heat treated. If the file slides over
such a test may enable you to select a metal suitable for
the material and the file teeth are dulled, the material is
the job being performed.
EXTREMELY HARD and has been heat-treated.
The file hardness test is simple to perform. You may
The file test is not a scientific method. It should not
hold the metal being tested in your hand and rested on
be used when positive identification of metal is
a bench or put it in a vise. Grasp the file with your index
necessary or when an accurate measurement of
finger extended along the file and apply the file slowly
hardness is required. Tests already described should be
but firmly to the surface being tested.
used for positive identification of metals. Special
If the material is cut by the file with extreme ease
machines, such as the Rockwell and Brinell testers,
and tends to clog the spaces between the file teeth, it is
should be used when it is necessary to determine
accurately the hardness of the material.
VERY SOFT. If the material offers some resistance to
15-30
