Figure 2-5.Sectional view of rivnut showing head and end
Hi-shear rivets are identified by code numbers
similar to the solid rivets. The size of the rivet is
measured in increments of thirty-seconds of an inch
for the diameter and sixteenths of an inch for the grip
length. For example, an NAS 1055-5-7 rivet would be
a hi-shear rivet with a countersunk head. Its diameter
would be 5/32 of an inch and its maximum grip length
would be 7/16 of an inch.
The collars are identified by a basic code number
and a dash number that correspond to the diameter of
the rivet. An A before the dash number indicates an
aluminum alloy collar. The NAS528-A5 collar would
be used on a 5/32-inch-diameter rivet pin. Repair
procedures involving the installation or replacement
of hi-shear rivets generally specify the collar to be
The rivnut is a hollow rivet made of 6063
aluminum alloy, counterbored and threaded on the
inside. They are manufactured in two head styles, flat
and countersunk, and in two shank designs, open and
closed ends. See figure 2-5. Each of these rivets is
available in three sizes: 6-32, 8-32, and 10-32. These
numbers indicate the nominal diameter and the actual
number of threads per inch of the machine screw that
fits into the rivnut.
Open-end rivnuts are the most widely used, and
are recommended in preference to the closed-end
type. However, in sealed flotation or pressurized
compartments, the closed-end rivnut must be used.
Fasteners on aircraft are designed for many
different functions. Some are made for high-strength
requirements, while others are designed for easy
installation and removal.
Lock-bolt fasteners are designed to meet
high-strength requirements. Used in many structural
applications, their shear and tensile strengths equal or
exceed the requirements of AN and NAS bolts.
The lock-bolt pin, shown in view A of figure 2-6,
consists of a pin and collar. It is available in two head
styles: protruding and countersunk. Pin retention is
accomplished by swaging the collar into the locking
grooves on the pin.
The blind lock bolt, shown in view B of
figure 2-6, is similar to the self-plugging rivet shown
in figure 2-3. It features a positive mechanical leek
for pin retention.
The hi-lok fastener, shown in figure 2-7, com-
bines the features of a rivet and a bolt and is used for
high-strength, interference-free fit of primary
structures. The hi-lok fastener consists of a threaded
pin and threaded locking collar. The pins are made of
Figure 2-6.Lock bolts.