Volvo Penta TAD420VE, Workshop Manual

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7
General Information Group 20
Tightening torque
For the correct tightening torque for critical joints,
which must be tightened using a torque wrench is lis-
ted under chapter “Tightening Torque”. For correct
tightening torque, is it important to apply cleaned th-
reads, bolt heads and mating surfaces, with lightly oi-
led or dry threads. In places where grease, locking or
sealing agents is required for screwed joints, the cor-
rect torque is stated in “Tightening Torque”.
When no tightening torque is stated, use the general
tightening torque, according to the table below.
Dimension Tightening torque
Nm (lbf.ft.)
M5 ......................................................... 6 (4.4)
M6 ......................................................... 10 (7.4)
M8 ......................................................... 25 (18.4)
M10 ....................................................... 50 (36.9)
M12 ....................................................... 80 (59.0)
M14 ....................................................... 40 (103.3)
Lock nuts
Do not reuse lock nuts that have been removed during
disassembly operations as these have reduced
service life when reused. Use new nuts when
assembling or reinstalling.
For lock nuts with a plastic insert such as Nylock®
the tightening torque stated in the table is reduced if
the Nylock® nut has the same head height as a stan-
dard hexagonal nut without plastic insert.
Reduce the tightening torque by 25% for bolt size M8
or larger.
If Nylock® nuts are higher, or of the same height as a
standard hexagonal nut, the tightening torque’s given
in the table applies.
Tightening torque with
protractor tightening
(angle tightening)
Tightening using both a torque setting and a protractor
angle requires that first the recommended torque is
applied using a torque wrench and then the recom-
mended angle is added according to the protractor
scale. Example: A 90°
protractor tightening means
that the joint is tightened a further 1/4 turn in one ope-
ration after the stated tightening torque has been app-
lied.
Strength classes
Bolts and nuts are divided up into different classes of
strength, the number on the bolt head indicates the
class. A high number indicates stronger material, for
example a bolt marked 10-9 indicates a higher
strength than one marked 8-8.
It is therefore important that bolts removed during the
disassembly of a bolted joint must be reinstalled in
their original position when assembling the joint.
When replacing a bolt, check in the spare parts cata-
logue to make sure the correct bolt is used.