Six Lobed Socket Head Fasteners; Prevailing Torque Fasteners - GMC 1989 Light Duty Truck Repair Manual

OA-4 GENERAL INFORMATION
products are desig ned to new, international standards that
m ay not yet be m anufactured by som e non-dom estic bolt
a n d n u t s u p p lie rs . In g e n e r a l, e x c e p t fo r s p e c ia l
applications, the com m on sizes and pitches are:
M 6.0 x 1 M 10 x 1.5
M 8 x 1.25 M 1 2 x 1 .7 5
SIX LOBED SOCKET
HEAD FASTENERS
Six lobed socket head (Torx) fasteners are used in som e
applications on vehicles covered in this m anual (figure
15). T h e door striker bolt is of this design.
Tools d e s ig n e d for th e s e fa s te n e rs
com m ercially. However, in som e cases, if the correct tool
is not available, a hex socket head w rench m ay be used.

PREVAILING TORQUE FASTENERS

A prevailing to rq ue nut is d esig n e d to d evelop an
interference betw een the nut and bolt threads. This is
most often accom plished by distortion of the top of an
all-m etal nut by using a nylon patch on the th reads in the
m iddle of the hex flat. A nylon insert m ay also be used as
a m ethod of interference betw een nut and bolt th reads
(figure 16).
A prevailing torque bolt is d esig ned to develop an
interference betw een bolt and nut threads, or the threads
of a tap p ed hole. This is accom plished by distorting som e
of the th reads or by using a nylon patch or adhesive
(figure 16).
RECOMMENDATIONS FOR REUSE:
1. C lea n , unrusted prevailing torque nuts and bolts
m ay be reused as follows:
2. Bolts and nuts which are rusty or d am a g e d should
be replaced with new parts or eq u al or g reater
strength.
are a v a ila b le
a. C lea n dirt and other foreign m aterial off the
nut or bolt.
b. Inspect the nut or bolt to insure there are no
cracks, elongation, or other signs of ab u se of
overtightening. (If th ere is any doubt, replace
with a new prevailing torque fas ten er or equal
or g reater strength.)
c. A ssem b le the parts and hand start the nut or
bolt.
d. O b s e r v e t h a t, b e fo r e
develops torque per the ch art in figure 13 (if
th e re is a n y d o u b t, r e p la c e
prevailing torque fas ten er of equal or g reater
strength).
e. Tighten the fas ten er to th e torque specified in
the ap propriate section of this m anual.
f a s t e n e r s e a ts , it
w ith a n ew