Torque wrench with an extension? Does it matter?

If using an socket extension on a torque wrench, does it affect the reading? If so why? Just about every bolt has a torque specification but some bolts cant be reached without an extension.

 

I have friend who are either shop owners or work in shops and I see them use extensions all the time. I often do. There are just some fasteners that there is no other way. If the extension isn't 'rubber' then I'd bet there is no or negligible difference.

 

Its my opinion that as long as the extension is in line with the point of rotation there should be a negligible torque difference since once you load the fastener all slack should be removed and torque application won't change.

Now if you use an extension which moves out further than the point of rotation you must use a formula to adjust for correct torque application.

Couldn't imagine where you would need to use an extension like that unless maybe for some sort of special reach crows foot

 

The margin of error in the reading by using an extension is totally negligible (unless you are doing something gnarly like adapting down to a 1/4 drive extension on a 1/2 drive torque wrench.) Actually, its probably less than the variations from one torque wrench to the other. When I was a machine builder, my SK torque wrenches had to be sent out and calibrated in order for the assembly part of our shop to be ISO certified. The variations in calibration from manufacturer to manufacturer is probably a wider margin than using and extension vs not using one.

 

Depends on which end the extension is on. If it is on the handle, no worries. Buy if it is on the drive end, the extension may increase the torque. It also depends on the angle the extension is at with respect to the wrench.

cf http://www.engineersedge.com/manufacturing_spec/torque_wrench_1.htm

 

A standard extension will not affect torque values since it is inline with the axis of rotation. However if you install a crowsfoot or other offset you must keep it 90 degrees to the line of the handle, or do some math calculations.
I would be more concerned with the type of lubricant used on the bolt and threads. This really affects the bolt stretch and clamping load.

 

Perfectly said :gp:

 

X2.
As long a the extension isn't twisting (plasticity) no problem.
Dead righton lubrication. Many ARP fasteners have different torque specs depending on whether you are using engine oil or there own assembly lube

 

OK, one of my brothers-in-law is a trucker and asked me about using an extension to torque the lug nuts on his semi tractor and trailer wheels. I wasn't thinking of just an extension from the square drive to the socket. What I posted above applies if you have a crow's foot, as has been mentioned. :grin:

 

A standard extension will not affect torque values since it is inline with the axis of rotation. However if you install a crowsfoot or other offset you must keep it 90 degrees to the line of the handle, or do some math calculations.???


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The picture below shows how adding the distance of "B" affects the torque applied to the bolt or nut would be increased with the leverage increased.




This link does the calculations for you.
https://www.motorcraftservice.com/renderers/torquewrench/wrench_formula_en.asp?type=180degstraight