Honda Motorcycle Service Manual page 17

GENERAL INFORMATION
It
must be noted that, in this control method using torque
values, the axial tension is proportional to the torque under
certain conditions. Under other conditions, this important axial
tension varies even when the fastener is tightened to the same
torque.
/
Threaded oortion Kerosene 0ile2
in a dry state applied (p= 0.09-0.14)
(p=O.35-0.54) (p=O.22-0.34)
The table on the right gives some examples of friction
coefficient<fl>when oil has adhered to the threaded portion.
Under the same conditions from the viewpoint of the
tightening torque and the material of the parts that are
fastened together,<~>varies largely. Of the tightening
torque applied on an unlubricated fastener, 88 to 9 2 percent
is consumed by the friction of flanges and thread surfaces and
only 8 to 12 percent is effectively transformed into axial
tension. This percentage of transformation into axial tension
increases as the above-mentioned friction decreases: i.e. as
the value<il>decreases, the axial tension increases. Axial
tension varies when the same tightening torque value is
obtained. Furthermore, in a dry (unlubricated) state, the value
<p>varies in a wider range and has a tendency to increase
as the tighteninglloosening procedure is repeated
It is important to oil the threads of specific fasteners when in-
structed to do so in the Model Specific manual. Oiling the
threads of these fasteners ensures stable fastening tension in
critical areas. No other bolts besides those specifically pointed
out in the Model Specific service manual text require oil on
their threads.
Lubrication of the threaded portion or of the bottom of the
flange reduces friction and the anti-loosening effect. However,
this lubrication also increases fastener axial tension and
results in a sufficient tightening strength, so that the fastener
is less likely to loosen.
Torque values are determined according to fastener size and
strength, and the strength of the parts that are fastened
together. In many of our previous service manuals, torque
values are specified within a certain range. Due to slight varia-
tion in torque wrench precision and fastener friction co-
efficient, the target torque value should be the middle of the
range of the torque value specified. The Model Specific
manuals provide only the simplified, middle-range torque
values. Kg-m is used as a tightening torque unit.
Example; A torque of 1 kg-m refers to the moment of force ob-
tained when a 1-meter long wrench is loaded with 1 kilogram.
At the same moment, a heavier load is needed as the effective
wrench length is shorter.
1 k g - m = l O N - m
1 kg-m =
7
ft-lb
Effect of Friction Coefficient<lr>
C
I
A
TIGHTENING TORQUE
=
1 kg-m
(1 0 0 kg-cm)
(20 cm)
= 1 kg-m
(1 0 0 kg-cm)
Date of Issue: March, 1995
O
HONDA MOTOR CO.,LTD.
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