02Jul
Introduction to Torque Part 5
Torque Conversion Factors
The below formulas and information provide guidance on different conversion factors e.g. the effect of torque wrench extensions.
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Units to be converted
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S.I. Units
|
Imperial Units
|
Metric Units
|
|
cN·m
|
N·m
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ozf·in
|
lbf·in
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lbf·ft
|
Kgf·cm
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Kgf·m
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1 cN·m =
|
1
|
0.01
|
1.416
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0.088
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0.007
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0.102
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0.001
|
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1 N·m =
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100
|
1
|
141.6
|
8.851
|
0.738
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10.20
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0.102
|
|
1 ozf·in =
|
0.706
|
0.007
|
1
|
0.0625
|
0.005
|
0.072
|
0.0007
|
|
1 lbf·in =
|
11.3
|
0.113
|
16
|
1
|
0.083
|
1.152
|
0.0115
|
|
1 lbf·ft =
|
135.6
|
1.356
|
192
|
12
|
1
|
13.83
|
0.138
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|
1 kgf·cm =
|
9.807
|
0.098
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13.89
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0.868
|
0.072
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1
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0.001
|
|
1 kgf·m =
|
980.7
|
9.807
|
1389
|
86.8
|
7.233
|
100
|
1
|
Formulae
Accepted formulae relating torque and tension, based on many tests are: -
For Imperial Sizes
These formulae may be used for bolts outside the range of the tables.
Formula for Calculating the Effect of Torque Wrench Extensions
M1 = M2 x L1/L2
Where L1 is the normal length and L2 is the extended length, M1 is the set torque and M2 the actual torque applied to the nut.
Example
The required torque on the fastener is 130 N·m (M2) but what do you set on the torque wrench scale?
L1 = 500 L2 = 650
(units of length not important, this is ratio)
M1 = 130 x 500/650
M1 = 100