# Improvised Torque Wrench

## Improvised torque wrench with 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 lb _{f} in*

* = 10 lb_{f} ft*

### "*Luggage Weight - Wrench*" Online Torque Calculator

m - Scale Reading (kg, lb_{f})

a - Wrench Length (m, in)

SIImperial

### Scale Wrench Torque Diagram - SI units

#### 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*