F
OR
M
ODELS
: JGI, JGM, JGN, JGP
AND
JGQ
S
ECTION
1 - D
ESIGN
S
PECIFICATIONS
& D
ATA
PAGE 1-20
most torque wrenches are not accurate over their entire range.
3.
Tighten all multi-bolt assemblies in steps (need not apply to Grade 5 cap screws).
Tighten each cap screw until snug using an alternating (criss-cross) pattern. Next,
tighten each cap screw to 25 percent of full torque, moving across from cap screw
to cap screw, in an alternating (criss-cross) pattern. Repeat this step for 50, 75,
and 100 percent of full torque. For main bearing and connecting rod bolts repeat
the 100 percent step to be sure that all fasteners are properly torqued.
4.
Always apply a steady slow force to a torque wrench, do not jerk it. When a torque
wrench is jerked the amount of torque applied can be as much as one and a half
times the amount set on the wrench. For example, if a wrench is set at 80 lb
f
-ft
(108 N·m) but is jerked, 120 lb
f
-ft (163 N·m) torque can be applied.
5.
Always do the final tightening with a torque wrench. Do not tighten the fastener
with a ratchet or impact wrench and then “check” the torque with a torque wrench.
6.
Do not double tap a torque wrench. Rapidly double tapping a torque wrench will
make the torque on the bolt more than what is set by a significant amount.
7.
When checking a tightened fastener torque, set torque wrench to proper required
torque value and slowly apply a steady force until the click is felt.
8.
Always reset the torque wrench to its lowest setting when the job is complete. If
the torque wrench is left in a high setting the spring in it is stressed and will
become inaccurate with time. If the torque wrench is put back to its lowest setting
the spring will relax and retain its accuracy.
9.
Do not use a torque wrench to break fasteners loose as it may overload the torque
wrench and/or cause loss of calibration.
10. For applications requiring the use of a boxed end or crowsfoot adapter with a
torque wrench to reach not readily accessible fasteners, the torque wrench setting
will not be the actual torque applied to the fastener. The exception is when the
adapter is 90 degrees to the torque wrench. The torque will be the same as on the
wrench scale.
11.
The ratio of actual torque at the fas-
tener with that on the wrench scale is a
function of the adapter's length and its
position in relation to the torque
wrench beam and the location on that
at which the force is applied, see fig-
ure.
L
A
F
IGURE
1-3 T
ORQUE
W
RENCH
WITH
A
NGLED
A
DAPTER
Force
Tw
Ta
L
L
A
+
-------------
⎝
⎠
⎛
⎞
=
Tw = Torque wrench setting, lb
f
-ft or N·m
Ta = Torque required at fastener, lb
f
-ft or N·m
L
= Length of wrench, ft or m (from square drive end to center point of force on
handle)
A = Length of adapter, ft or m (measured through end of adapter on a line
parallel to the center line of the wrench)
12. When studs are specified for cylinder applications, tighten stud-nuts to the same
