I had a discussion with a buddy here at work about how torque wrenches change torque depending on how long of an extension you have on it.

Is there a rule for this? I swear I read something about -1 lb/ft per 10" extension or so.

 

An extension on the socket side? in a perfect world there would be no correction factor... But seeing how the extension could in theory twist a bit between the socket and the wrench its possible the reading would be off a bit. but I don't think it would matter much.

 

no matter how long of extension you have, it will not differ the torque.
http://wiki.answers.com/Q/If_you_add_an_ex...ange_the_torque

 

^ yup .. the flex you get with an extension is negligible while torquing down.

 

no change on the socket side(axis of rotation), you get more rotational force if you add extension to the handle side.

on the side note: when you are using a breaker bar, keep the darn thing at 90 degree bend, at right angle you have the max torque.

 

^What he said. It will change the torque, but almost negligibly. Use as few extensions as possible and its all good.

 

agreed... if you have a socket extension the torque rating would change but so minimally that it wouldn't matter!


Some people have a bar with a male end one side and a female socket about 1 metre up, this allows you to plug in a 60Nm torque wrench and effectively it will click one 200+Nm are applied due to the extended length of the force. there are websites that can be found through google to help with calculations and also fabricating the needed tool

 

If you use a straight extension the torque at the fastener and the head of the torque wrench will be the same no matter how long the extensions are. That's why there's never a length specified for extensions in repair manuals.

What may change is how far you have to turn the torque wrench to achieve any given torque. Lots of extensions means they'll twist up more so you'll have to turn the wrench more to get the same torque, but the torque will be the same. When using lots of extensions the amount of twist can be pretty big!

If you use a crow's foot adapter that will change torque depending on a number of factors. If you use an impact gun then the flexibility of the extensions have a huge effect.

 

I don't see that extending the handle will change the setting on a click type torque wrench either. Extending the handle will only allow you to apply the same torque to the bolt while applying less force on the handle. The torque vs. setting only changes if you extend the torque wrench with an adaptor in line with the handle and you do it on the head side. Am I missing something?

 

Thats what I think. Desired torque may be reached with less force on the handle because of added leverage but the actual force applied would be the same with or without extensions.