clog the file teeth, it is SOFT. If the material offers
considerable resistance to the file but can be filed by
repeated effort, it is HARD and may or may not have
This chapter has given you a thorough overview
of basic metallurgy. Remember, it is basic information
been heat treated. If the material can be removed only
only, and you will need to learn specific applications
by extreme effort and in small quantities by the file
through experience and by further study in the appro-
teeth, it is VERY HARD and has probably been heat
priate technical manuals. Always ask a senior member
treated. If the file slides over the material and the file
of your division to explain anything in this chapter or
teeth are dulled, the material is EXTREMELY HARD
in your work that you do not fully understand.
and has been heat treated.
You have been introduced to stresses and strains,
The file test is not a scientific method. It should
the structure, properties, and types of metals, and the
not be used when positive identification of metal is
ways in which metals are classified, marked, and
necessary or when an accurate measurement of hard-
tested. Go back now and review any of these areas that
you do not understand.
ness is required.