| Garage Guy |
02-15-2012 11:33 AM |
Quote:
Originally Posted by jpharrell
(Post 629392)
4) If you must use an extension straight in line with the handle of a torque wrench you should be very careful. The torque applied to the bolt will be greater than the value you set on the torque wrench and the correction factor depends on both the length of the extension and the moment arm of the force application. It is not just the length of the torque wrench handle that counts, it is also dependent on where you apply the force on the handle.
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This is a really important point. Some of us have been referring to "length of the torque wrench" to mean "how far from the head of the torque wrench you are applying the force", but to be clear it is that distance, not the manufactured length of the wrench, that is important here (assuming a click-type wrench anyway). If you have a 12" torque wrench and for some reason are choking up on it applying the force halfway at 6" from the head, you need use 6" as the torque wrench length in the formula for torque at the business end of the extension. If you add a 12" cheater so you are applying the force at 24" from the head of the wrench, use 24" as the torque wrench length in the formula. If you are applying the force at 12" from the head of the wrench, and using Allan's 3" extension, use a factor of 0.8 :). Beam-type wrenches are designed to be used by applying force at one particular distance from the head, and that's the length you should use.
Of course as Larry and various other folks have been pointing out at length (pun intended, I guess) where you apply the force on the wrench doesn't matter if you are using a click-type wrench in the usual way, without an extension. It will measure the torque at the head of the wrench and that's all you want in that case.
--Paul
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