How is torque actually measured when using a torque wrench?

In summary, there are three cases for measuring torque applied to a nut when using a torque wrench with a crow foot extension. Case 1 states that the torque remains the same regardless of the extension's position, as long as it is at a 90 degree angle to the wrench. However, in Case 2, it is mentioned that the distance from the handle to the nut should be kept the same as the distance from the handle to the pivot point in order for the torque to remain constant. Lastly, Case 3 suggests that the distance for torque measurement should be from the handle to the nut, perpendicular to the applied force. It is concluded that Case 1 is the correct method, while Case 3 may be used in certain situations
  • #1
korwynkim
3
0
wqoF5KW.png

Take this picture for example. Assume this picture represents a torque wrench applying torque on a nut, and a force F is applied at the centre of the black handle perpendicular to it. The force applied to the nut is:

Torque = Fd

There are times when a nut is in a very inconvenient location and you can't fit a torque wrench on it. Sometimes, a crow foot extension will be able to reach it. The problem is, changing the lever arm changes the torque.

Case 1: The common knowledge is that if the extension is at 90 degrees to the torque wrench, the torque applied to the nut doesn't change.

Torque = Fd (regardless of x)
vIkcW7g.png


Case 2: I have also heard that in order for the torque to remain the same, the distance from the handle of the wrench to the nut should be kept the same as the distance from the handle to the pivot point.

Torque = Fy = Fd
D3nTfxw.png


Case 3: Distance for torque should be measured from the handle to the nut perpendicular to the force applied.

Torque = Fx
P3F38G1.png


What is the correct method to measure torque applied to the nut?
 
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  • #2
Case 1 is correct. Case 3 is also correct, but is obviously less mechanically advantageous, unless it gets you round an awkward obstacle.
Case 2 is not correct. For this to work, the force would have to be perpendicular to y.
 

1. How does a torque wrench measure torque?

A torque wrench measures torque by using a spring-loaded mechanism to apply a specific amount of force to a bolt or nut. The amount of force applied is measured and displayed on a scale, giving the user an accurate reading of the torque being applied.

2. What units are typically used to measure torque with a torque wrench?

The most commonly used units for torque measurement are foot-pounds (ft-lb) and Newton-meters (Nm). These units indicate the amount of force applied to a bolt or nut, with foot-pounds being the standard unit in the United States and Newton-meters being used in most other countries.

3. How accurate are torque wrench measurements?

The accuracy of torque wrench measurements can vary depending on the type and quality of the wrench. However, most torque wrenches have an accuracy range of +/- 4% or better, meaning they can measure torque within 4% of the actual value being applied.

4. Can torque wrenches be calibrated?

Yes, torque wrenches can be calibrated to ensure their accuracy. It is recommended to have torque wrenches calibrated at least once a year, or more frequently if they are used regularly or in harsh environments.

5. Are there different types of torque wrenches for different applications?

Yes, there are different types of torque wrenches for different applications. Some common types include click torque wrenches, which make an audible click when the desired torque is reached, and digital torque wrenches, which display the torque measurement on a digital screen. There are also specialized torque wrenches for specific industries, such as aviation or automotive.

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