Six Lobed Socket Head Fasteners; Prevailing Torque Fasteners - Chevrolet 1988 Light Duty Truck Repair Manual

OA-4 GENERAL INFORMATION
products are designed to new, international standards that
may not yet be m anufactured by some non-dom estic bolt
and n u t s u p p lie rs . In g e n e ra l, e x c e p t fo r s p e c ia l
applications, the common sizes and pitches are:
M6.0 x 1 M 1 0 x 1 .5
M8 x 1.25 M 1 2 x 1 .7 5
SIX LOBED SOCKET
HEAD FASTENERS
Six lobed socket head (Torx) fasteners are used in some
applications on vehicles covered in this manual (figure
15). The door striker bolt is of this design.
Tools d e s ig n e d fo r th e se fa ste n e rs are a va ila b le
comm ercially. However, in some cases, if the correct tool
is not available, a hex socket head wrench may be used.

PREVAILING TORQUE FASTENERS

A prevailing torque nut is designed to develop an
interference between the nut and bolt threads. This is
most often accom plished by distortion of the top of an
all-metal nut by using a nylon patch on the threads in the
m iddle of the hex flat. A nylon insert may also be used as
a method of interference between nut and bolt threads
(figure 16).
A prevailing torque bolt is designed to develop an
interference between bolt and nut threads, or the threads
of a tapped hole. This is accom plished by distorting some
of the threads or by using a nylon patch or adhesive
(figure 16).
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 of
overtightening. (If there is any doubt, replace
with a new prevailing torque fastener or equal
or greater strength.)
c. Assem ble the parts and hand start the nut or
bolt.
d. O b s e rv e th a t, b e fo re fa s te n e r s e a ts , it
develops torque per the chart in figure 13 (if
th e re is an y d o u b t, re p la c e w ith a new
prevailing torque fastener 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 or equal or greater
strength.