# 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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