control parts, wing covering, or similar parts of the
aircraft.
6. Minimum rivet diameter is equal to the
thickness of the thickest sheet to be riveted.
7. Maximum rivet diameter is three times the
thickness of the thickest sheet to be riveted.
8. The proper length of rivet is an important part
of the repair. If the rivet is too long, the formed head
will be too large, or the rivet may bend or be forced
between the sheets being riveted. If the rivet is too
short, the formed head will be too small or the riveted
material will be damaged. The length of the rivet
should equal the sum of the thickness of the metal
plus 1 1/2 times the diameter of the rivet, as shown in
figure 13-43. The formula for determining rivet
length is as follows:
1 1 / 2 x D + G =L
Where:
D = the rivet diameter,
G = the grip (total thickness of material, and
L = the total length of the rivet.
Spacing and Edge Distance
Rivet spacing, also referred as rivet pitch, is the
distance between the rivets in the same row, and is
measured from the rivet center to the rivet center.
Transverse pitch is the distance between the rows of
rivets, and is measured from the rivet center to rivet
center. Edge distance is the distance from the center
of the rivet to the edge of the material being riveted.
Figure 13-43.—Rivet length.
There are no specific rules that apply to every
case or type of riveting. There are, however, certain
general rules that should be followed.
RIVET SPACING.—Rivet spacing (pitch)
depends upon several factors, principally the
thickness of the sheet, the diameter of the rivets, and
the manner in which the sheet will be stressed. Rivet
spacing should never be less than three times the rivet
diameter. Spacing is seldom less than four times the
diameter nor more than eight times the diameter.
TRANSVERSE PITCH.—When two or more
rows of rivets are used in a repair job, the rivets
should be staggered to obtain maximum strength.
The distance between the rows of rivets is called
“transverse pitch.”
Transverse pitch is normally
75 percent of existing rivet pitch, but should never be
less than 2 1/2 times the diameter.
EDGE DISTANCE.—The edge distance for all
rivets, except those with a flush head, should not be
less than twice the diameter of the rivet shank nor
more than four times the diameter of the rivet shank.
Flush-head rivets require an edge distance of at least
2 1/2 times the diameter. If rivets are placed to close
to the edge of the sheet, the sheet is apt to crack or pull
away from the rivets. If they are placed too far away
from the edge, the sheet is apt to turn up at the edge.
NOTE: On most repairs, the general practice
is to use the same rivet spacing and edge
distance that the manufacturer used in the
surrounding area, or the structural repair
manual for the particular aircraft may be
consulted, Figure
and edge distance.
13-44 shows rivet spacing
Figure 13-44.—Rivet spacing and edge distance.
13-27
