Drilling Rivet Holes
Standard twist drills are used to drill rivet holes.
Table 13-2 specifies the size drill to be used with the
various size rivets.
Note that there is a slight
clearance in each case. This prevents binding of the
rivet in the hole.
Locations for the rivet holes should be center
punched and the drilling done with a power drill,
either electric or pneumatic. Electric drills constitute
a fire hazard when you are drilling on or near an
aircraft. The hazard is caused by the arcing of the
brushes. Therefore, the pneumatic drill should be
used. The center punch mark should be large enough
to prevent the drill from slipping out of position, but
must not be made with enough force to dent the
surrounding material. All burrs must be removed by
using a larger size drill or by using a deburring tool.
Flush Riveting
In aircraft construction, manufacturers are
eliminating protruding-head rivets on the exterior
surfaces.
In fabricating stressed metal skin, all
exposed rivet heads must be countersunk to lie flush
with the outer surface of the skin. It is essential to
provide an aerodynamically smooth surface. See
figure 13-45.
Flush rivets are more difficult to install because
the parts being riveted must be countersunk. Another
hazard is the closeness of the rivet set to the metal
during riveting. If considerable skill is not used, the
metal will be damaged by the rivet set. Flush rivets
are made with heads of several different angles, but
the 100-degree rivet is standard for all Navy aircraft.
The two methods used to countersink flush rivets
are dimple and machine countersinking. In some
instances, a combination of the two may be used; in
other words, the top sheet of an assembly may be
dimpled while the under sheet is machine
countersunk.
Rivet Driving
Before driving any rivets, make sure all the holes
line up perfectly, all the shavings and burrs have been
removed, and the parts to be riveted are fastened
securely together. It is important that the sheets be
held firmly together near the area of the rivet being
driven.
Table 13-2.—Drill Sizes for Various Size Rivets
To adjust the speed of the gun, place it against a
block of wood. Never operate a rivet gun without
resistance against the set. The vibrating action may
cause the retaining spring to break, allowing the set to
fly out.
WARNING
A rivet set can be a deadly weapon. If a
rivet set is placed in a rivet gun without a
set retainer and the throttle of the gun is
opened, the rivet set may be projected like
a bullet. This may cause severe injury to a
person or destruction of equipment.
Figure 13-45.—Incorrect countersinking.
13-28
