equal the sum of the thickness of the metal plus 1 1/2
times the diameter of the rivet, as shown in figure 4-43.
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 to as rivet pitch, is the
distance between the rivets in the same row, and is
measured from the rivet center to the rivet center.
Figure 4-44.--Rivet spacing and edge distance.
Transverse pitch is the distance between the rows of
rivets, and is measured from the rivet center to rivet
EDGE DISTANCE.--The edge distance for all
center. Edge distance is the distance from the center of
rivets, except those with a flush head, should not be less
the rivet to the edge of the material being riveted.
than twice the diameter of the rivet shank nor more than
four times the diameter of the rivet shank. Flush-head
There are no specific rules that apply to every case
rivets require an edge distance of at least 2 1/2 times the
or type of riveting. There are, however, certain general
diameter. If rivets are placed to close to the edge of the
rules that should be followed.
sheet, the sheet is apt to crack or pull away from the
RIVET SPACING.--Rivet spacing (pitch)
rivets. If they are placed too far away from the edge, the
depends upon several factors, principally the thickness
sheet is apt to turn up at the edge.
of the sheet, the diameter of the rivets, and the manner
NOTE: On most repairs, the general practice is to
in which the sheet will be stressed. Rivet spacing
use the same rivet spacing and edge distance that the
should never be less than three times the rivet diameter.
manufacturer used in the surrounding area, or the
Spacing is seldom less than four times the diameter nor
structural repair manual for the particular aircraft may
more than eight times the diameter.
be consulted. Figure 4-44 shows rivet spacing and edge
TRANSVERSE PITCH.--When two or more
distance.
rows of rivets are used in a repair job, the rivets should
be staggered to obtain maximum strength. The distance
Drilling Rivet Holes
between the rows of rivets is called "transverse pitch."
Standard twist drills are used to drill rivet holes.
Transverse pitch is normally 75 percent of existing rivet
Table 4-2 specifies the size drill to be used with the
pitch, but should never be less than 2 1/2 times the
various size rivets. Note that there is a slight clearance
diameter.
in each case. This prevents binding of the rivet in the
hole.
Table 4-2.--Drill Sizes for Various Size Rivets
Rivet Diameter
Drill No.
Drill Size
3/32
No. 41
0.0960
1/8
No. 30
.1285
5/32
No. 21
.1590
3/16
No. 11
.1910
1/4
No. F
.2570
5/16
No. P
.3230
3/8
No. W
.3860
Figure 4-43.--Rivet length.
4-24
