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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