Tightening Sequences And Procedures - Jeep cherokee 1989 Owner's Manual

0-1 2
while smaller studs carry a geometric code to denote grade.
It should be noted that many fasteners, especially Grades 0 through
2, have no distinguishing marks on them. When such is the case, the
only way to determine whether it is standard or metric is to measure
the thread pitch or compare it to a known fastener of the same size.
Standard fasteners are often referred to as SAE, as opposed to
metric. However, it should be noted that SAE technically refers to a
non-metric fine thread fastener only. Coarse thread non-metric
fasteners are referred to as USS sizes.
Since fasteners of the same size (both standard and metric) may have
different strength ratings, be sure to reinstall any bolts, studs or nuts
removed from your vehicle in their original locations. Also, when re-
placing a fastener with a new one, make sure that the new one has
a strength rating equal to or greater than the original.
Standard (SAE and USS) bolt dimensionslgrade marks
G Grade marks lbolt strength)
L Length
inches)
T Thread pitch (number o f threads per inch)
D Nominal diameter (in inches)
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Metric thread sizes
M-6
M-8
M-10
M-12
M-14
Pipe thread sizes
1/2
thread sizes
20
-
5/16 1 8 . .
511 6 - 2 4 .
318 1 6 . .
-
318 - 2 4 .
1 4 . .
-
7/16 2 0 .
-
112 - 1 3 . .

Tightening sequences and procedures

Most threaded fasteners should be tightened to a specific torque
value (torque is the twisting force applied to a threaded component
such as a nut or bolt). Overtightening the fastener can weaken it and
cause it to break, while undertightening can cause it to eventually come
loose. Bolts, screws and studs, depending on the material they are made
of and their thread diameters, have specific torque values, many of
which are noted in the Specifications at the beginning of each Chapter.
Be sure to follow the torque recommendations closely. For fasteners
not assigned a specific torque, a general torque value chart is presented
here as a guide. These torque values are for dry (unlubricated) fasteners
threaded into steel or cast iron h o t aluminum). As was previously men-
tioned, the size and grade of a fastener determine the amount of torque
that can safely be applied to it. The figures listed here are approximate
Nmlm
38 to 54
68 to 96
Metric bolt dimensionslgrade marks
P Property class lbolt strength)
L Length (in millimeters)
T Thread pitch (distance between threads i n millimeters)