Improvised Torque Wrench
Improvise a torque wrench with a luggage scale.
If you don't have a torque wrench available  or if you want to check the readings of the one you have  it is easy to improvise by using a standard wrench and a scale as indicated in the figure above.
The moment  or torque  can be calculated
T = F a (1)
where
T = moment or torque (Nm, lb_{f} ft)
F = applied force (N, lb_{f} )
a = length of the wrench (m, ft)
Note!  Most scales in the SI unit system measures weight  force due to the acceleration of gravity  in kg .
 the difference between mass and weight .
The reading from the scale can be converted to N by using
F = m g
where
m = reading of the scale (kg, lb_{f} )
g = acceleration of gravity (9.81 m/s^{2}, 32.17 ft/s^{2})
Example  Measuring Torque with a standard Wrench and a Luggage Scale  readings in kg
The reading of the scale at the end of the wrench is 10 kg . The length of the wrench is 0.3 m . The moment exerted can be calculated
T = (10 kg) (9.81 m/s^{2}) (0.3 m)
= 29.4 Nm
Example  Measuring Torque with a standard Wrench and a Luggage Scale  readings in lb_{f}
The reading of the scale at the end of the wrench is 20 lb_{f} . The length of the wrench is 6 in . The moment exerted can be calculated
T = (20 lb_{f} ) (6 in)
= 120 in lb_{f}
= 10 lb_{f} ft
" Luggage Weight  Wrench " Online Torque Calculator
Scale Wrench Torque Diagram  SI units
Download and print Scale Wrench Torque Diagram
Example  Torque Settings for a Cylinder Head
The torque settings for a cylinder head in a car engine are specified to 30 Nm.
According to the diagram above with a wrench with length 0.2 m  the scale readings should be approximately
14 kg
Scale Wrench Torque Diagram  Imperial units
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