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Torque wrench calculations

7K views 23 replies 9 participants last post by  Badger 
#1 ·
I heard a while back the formula for calculating the correct torque when using extensions but I can't remember it. Does anyone know how much you need to increase your torque when you have to use an extension on the torque wrench? I think it has something to do with the added flex between the wrench and the socket. ex: 1 ft# per inch of extension........thanks. I want to be sure I am torquing to the right specs.
 
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#4 ·
I represent that remark!
I did not know if that was true or not, I just wanted to be sure....thanks y'all.


[
Bladerunr said:
I think that only applies when you're working under a shade tree, or somewhere south of the Mason Dixon line.
I think that only applies when you're working under a shade tree, or somewhere south of the Mason Dixon line.
 
#6 ·
Using an extension on a torque wrench only REDUCESthe force you must apply on the handlein order to generate a given torque. For instance, if you are torquing something to a certain spec, and you add an extension that makes thehandletwice as long, then the force you need to apply is reduced by half. Flex in the handle+extension doesn't really enter into it because you are measuring the torque at the head.
 
#9 ·
#10 ·
Talking with the engineer that works for me he says if you have a 3/8's torque wrench with a 3" extension it will infact increase the amount of ftlbs at the socket. If you have a range of say 50-60 ftlbs set it for the lower limit 50 and you will end up with an increase of a few percent. Of course the longer the extension the more the torque is multiplied.
 
#11 ·
knyland said:
Talking with the engineer that works for me he says if you have a 3/8's torque wrench with a 3" extension it will infact increase the amount of ftlbs at the socket. If you have a range of say 50-60 ftlbs set it for the lower limit 50 and you will end up with an increase of a few percent. Of course the longer the extension the more the torque is multiplied.
As stated, using the extension adapter as shown in the above photo @ a right angle requires no correction. The torque wrench is set at 110 ft~lbs

If i use the tool as a torqueextension adapter the wrench is set at 82.5 ft~lbs




[*]
A = length of torque wrench = 15
[*]
B = length of adapter = 5
[*]
C = torque wrench setting to calculate
[*]
D = desired torque at end of extension = 110 ft~lbs[/list]


C = 110 (15/15+5) = 82.5
 
#12 ·
I think people are answering different questions here. Can you describe how/where the extension is being used in your example? Is it used to lengthen the handle or on the head of the wrench? Is it straight off the wrench or at some angle? Without getting too involved in the math, your layout will make a difference in the answer.
 
#13 ·
overheadcam427 said:
I think people are answering different questions here. Can you describe how/where the extension is being used in your example? Is it used to lengthen the handle or on the head of the wrench? Is it straight off the wrench or at some angle? Without getting too involved in the math, your layout will make a difference in the answer.
No question in my mind thatwarrior04 was referring to SOCKET EXTENSIONS, nada mas and the subject matter deviated to torque wrench adapters which isn't what he asked IMO

 
#17 ·
Bladerunr said:
A socket extension WILL reduce torque throughput of an impact wrench. This might be where the theory started. Wrench benders don't make good engineers.
I thought we were discussing torque wrenches
... there are specifictools madefor impact use that can take the higher torsional stresses
but you know that!
 
#18 ·
Yes I was refering to the use of socket extensions, not cheater bars. An example would be if I could not reach a certain nut with the socket directly on the head of the torque wrench, would I need to add or subtract from the torque setting if I were to use a 3" or 6" socket extension to reach the nut?
 
#19 ·
AlanH said:
Bladerunr said:
A socket extension WILL reduce torque throughput of an impact wrench. This might be where the theory started. Wrench benders don't make good engineers.
I thought we were discussing torque wrenches
... there are specifictools madefor impact use that can take the higher torsional stresses
but you know that!

Just tryin to figure where these strange ideas come from...
 
#21 ·
+1


Huskers said:
You do not need to recalculate torque settings while using a standard socket extension. Recalculations are only required if the overall length of the torquing device is changed, which is not the case with a socket extension.




This is true. I misunderstood your question in my original post -I thought you were referring to "cheater bars" and the like. The torque transmitted through the extension bar is the same at both ends.
 
#24 ·
Huskers said:
You do not need to recalculate torque settings while using a standard socket extension. Recalculations are only required if the overall length of the torquing device is changed, which is not the case with a socket extension.

That's true as long as the extension bar is straight. If it gets bent then the socket will not be directly inline with the pivot on the torque wrench
Well there has been a lot of bollocks spoken here. I just thought I'd add a bit more
 
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