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TIGHTENING
TORQUE AND TENSILE LOAD
. Application of the correct force (tensile
load) is essential for a reliable assembly:
- undertight fasteners can work loose;
- overtight fasteners may distort components or shear.
. Tensile load depends on tightening torque and
friction coefficient.
Tensile load (Fo)
The force in newtons (N) which maintains pressure
contact between assembled components.
Tightening torque (Cs)
The product of a force and the leverage length at
which it is applied: Torque (Nm) = Force (in newtons)
x Length (in metres).
HOW TIGHT A TORQUE ?
1. Always observe equipment manufacturer's
specifications.
2. If none are available, determine required torque
on a test rig.
3. Otherwise, refer to national standards.
Tightening torque table
Torque values are given for 85% fastener yield strength,
for class "A" torque control accuracy (< ±5%).
1. Friction coefficient
Actual friction coefficient depends on fastener
and component condition, and affects tightening. Choose
the appropriate table according to type of fasteners
used (i.e. µ = 0,10, 0,15 or 0,20).
2. Fastener grade
The grade of a fastener denotes its quality (best
is 12.9). Check the appropriate column for the fasteners
used.
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Tightening torque (Cs)
Torque values are listed in newton-metre (Nm)
for each type of fastener.
4. Tensile load (Fo)
This force in newtons (N) is the equivalent of
an Fomax value.
The above information,
for which Facom accepts no liability, is given
as a guide only. |
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Conversion
table :
The internationally accepted unit is the
newton-metre (Nm)
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1.
To convert Nm:
. Newton metres to kilogramme force metres
: 1 Nm = 0,102 kgf
m
. Newton metres to pound force feet : 1
Nm = 0,738 lbf ft
. Newton metres to pound force inches :
1 Nm = 8,851 lbf in
. Newton metres to ounce force inches :
1 Nm = 141,61 ozf
in |
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2.
To convert kgf m:
. Kilogramme force metres to newton metres
: 1 kgf m = 9,81 Nm
. Kilogramme force metres to pound force
feet : 1 kgf m = 7,23
lbf ft
. Kilogramme force metres to pound force
inches : 1 kgf m =
86,8 lbf in |
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3.
To convert lbf f:
. Pound force feet to newton metres : 1
lbf ft = 1,35 Nm
. Pound force feet to kilogramme force metres
: 1 lbf ft = 0,138
kgf m
. Pound force feet to pound force inches
: 1 lbf ft = 12 lbf
in |
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4.
To convert lbf in:
. Pound force inches to newton metres :
1 lbf in = 0,1129
Nm
. Pound force inches to kilogramme force
metres : 1 lbf in
= 0,0115 kgf m
. Pound force inches to pound force feet
: 1 lbf in = 0,083
lbf ft
. Pound force inches to ounce force inches
: 1 lbf in = 16 ozf
in |
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<%end if%>
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 Tightening
torques |
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