Improvised Torque Wrench
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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