Prevailing Torque Fasteners; Six Lobed Socket Head Fasteners - GMC G Service Manual

OA-16 GENERAL INFORMATION

PREVAILING TORQUE FASTENERS

A prevailing torque nut is designed to develop an inter­
ference between the nut and bolt threads. This is most
often accomplished by distortion of the top of an all-metal
nut by using a nylon patch on the threads in the middle of
the hex flat. A nylon insert may also be used as a method of
interference between nut and bolt threads (figure 19).
A prevailing torque bolt is designed to develop an inter­
ference between bolt and nut threads, or the threads of a
tapped hole. This is accomplished by distorting some of the
threads or by using a nylon patch or adhesive (figure 19).
RECOMMENDATIONS FOR REUSE:
1. Clean, unrusted prevailing torque nuts and bolts may
be reused as follows:
a. Clean dirt and other foreign material off the nut
or bolt.
b. Inspect the nut or bolt to insure there are no
cracks, elongation, or other signs of abuse or
n s n
N«m
4, 5
In. Lbs.
1,2, 3, 6, N*m
7, 8, 9
In. Lbs.
N*m
4, 5
In. Lbs.
N*m
1, 2, 3, 6,
8, 9
In. Lbs.
A. Metric Sizes
B. Inch Sizes
8
6 & 6.3 8 10
0.4 1.4
0.8
12
4.0 7.0
0.4
0.6 1.2
4.0 5.0 10
B
.250 .312 .375
0.4 0.6 1.4
4.0 5.0 12
0.4 0.6 1.0
5.0 9.0
4.0
1. Top Lock Type
2. Center Lock
3. Dry Adhesive Coating
4. Out Of Round Thread
5. Deformed Thread Profile
Figure 19 — Torque Nuts and Bolts Chart
overtightening. (If there is any doubt, replace
with a new prevailing torque fastener of equal or
greater strength.)
c. Assemble the parts and hand start the nut or
bolt.
d. Observe that, before fastener seats, it develops
torque per the chart in figure 19 (if there is any
doubt, replace with a new prevailing torque fas­
tener of equal or greater strength).
e. Tighten the fastener to the torque specified in
the appropriate section of this manual.
2. Bolts and nuts which are rusty or damaged should be
replaced with new parts of equal or greater strength.
SIX LOBED SOCKET
HEAD FASTENERS
Six lobed socket head fasteners are used in some appli­
cations on vehicles covered in this manual (figure 20). The
door striker bolt is of this design.
12 14
2.2 3.0
18 25
1.6 2.4
14 20
.437 .500
1.8 2.4
15 20
1.4 1.8
12 15
6. Nylon Strip Or Patch
7. Nylon Washer Insert
8. Nylon Patch
9. Nylon Insert
16
20
4.2
7.0
35 57
3.4
5.6
28
46
.562
.625 .750
3.2 4.2 6.2
27 35 51
2.6 3.4 5.2
22 28 43
B-02406