appropriate temperature until it is uniformly heated and then cooling
it in still air.
Only ferrous metals can be normalized, Case
hardening consists of carbonizing steel at 1,700 to 1,800F for
several hours and reheating and quenching twice.
Hot working
consists, in general, of working steel while the core is still hot.
Casting is the process of pouring molten metal into a single-purpose
or permanent mold. Hot rolling is passing the metal between rollers
while it is still hot.
Forging is changing a metal's shape by
compressive deformation through hammering or pressure.
Extrusion is
forcing metal to take the die opening's shape.
Metal worked at
temperatures below the critical range is being cold-worked.
Cold
rolling, cold drawing, and stamping and pressing are forms of cold
working.
PART D:
AVIATION HARDWARE
GENERAL
An aircraft made of the best materials and strongest parts is of no
value unless those parts are firmly held together.
Rivets and
special-purpose fasteners are the primary hardware used for this on
Army aircraft.
Both are used to hold two or more metal sheets,
plates, or formed pieces of material together.
Heads are formed on
one end of the rivet and special-purpose fastener when manufactured.
Special-purpose fasteners are used where high strength or a special
application of a fastener is required. The rivet is smooth-shanked;
its tip, opposite the head, is reshaped upon use to take the place of
a nut.
The shank of the rivet is placed through matched (aligned)
holes in two or more pieces of material, and the tip is then
flattened to form a second head that clamps the pieces together.
The second head, formed either by hand or by pneumatic equipment, is
called a shop head. The shop head works in the same manner as a nut
on a bolt. This section discusses the variety of rivets and special-
purpose fasteners in general use in Army aviation.
RIVETS
Many different metals and alloys of metals are used to make rivets.
The material used for the majority of aircraft rivets is an aluminum
alloy. Other metals used are steel and copper. Aluminum rivets have
a silver-white color; steel rivets are a typical steel color; and
copper rivets are copper color.
Aside from their metal, rivets are
divided into two main groups:
solid-shank and blind rivets.
The
following paragraphs discuss the two groups in detail.
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