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 3-6,
is similar to the self-plugging rivet shown in figure 3-3.
It features a positive mechanical lock for pin retention.
Hi-Lok Fasteners
The hi-lok fastener, shown in figure 3-8, combines
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
cadmium-plated alloy steel with protruding or
100-degree flush heads. Collars for the pins are made of
anodized 2024-T6 aluminum or stainless steel. The
threaded end of the pin is recessed with a hexagon
socket to allow installation from one side. The major
diameter of the threaded part of the pin has been
truncated (cut undersize) to accommodate a 0.004-inch
Figure 3-9.--Jo-bolt.
maximum interference-free fit. One end of the collar is
internally recessed with a 1/16-inch, built-in variation
head styles available for Jo-bolts are the 100-degree
that automatically provides for variable material
flush head, the hexagon protruding head, and the
thickness without the use of washers and without
100-degree flush millable head.
fastener preload changes. The other end of the collar
has a torque-off wrenching device that controls a
FASTENERS (THREADED)
predetermined residual tension of preload (10%) in the
fastener.
Although thousands of rivets are used in aircraft
construction, many parts require frequent dismantling
Jo-Bolt Fasteners
or replacement. For these parts it is more practical to
use some form of threaded fastener. Furthermore, some
The Jo-bolt, shown in figure 3-9, is a high-strength,
joints require greater strength and rigidity than can be
blind structural fastener that is used on difficult riveting
provided by riveting. Manufacturers solve this problem
jobs when access to one side of the work is impossible.
by using various types of screws, bolts, nuts, washers,
The Jo-bolt consists of three factory-assembled parts:
and fasteners.
an aluminum alloy or alloy steel nut, a threaded alloy
Bolts and screws are similar in that both have a
steel bolt, and a corrosion-resistant steel sleeve. The
head at one end and a screw thread at the other, but there
are several differences between them. The threaded end
of a bolt is always relatively blunt, while that of a screw
may be either blunt or pointed. The threaded end of a
bolt must be screwed into a nut, but the threaded end of
the screw may fit into a nut or other female
arrangement, or directly into the material being
secured. A bolt has a fairly short threaded section and a
comparatively long grip length (the unthreaded part); a
screw may have a longer threaded section and no
clearly defined grip length. A bolt assembly is
generally tightened by turning its nuts. Its head may or
may not be designed to be turned. A screw is always
designed to be turned by its head. Another minor but
Figure 3-8.--Hi-lok fastener.
3-5
