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torque wrench inadequecy??


Ferd/289

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Roughly calculated, on a 40 ft pound torque requirement, a 1/2 inch crow's foot extension would increase the actual torque by only 1 foot/pound. Well within the 36 - 43 ft/pd suggested setting for the pivot nut.

 

But that's also 2.5% error.

With a cheap wrench that has 6% error your adding a crowsfoot just turned that wrench to something with almost 9% error (and depending on which way it's calibrated closer...) With that error in there, you are at 43.6 ft-lbs exceeding the upper level of the torque specification. In that case you should torque to 39 ft-lbs to negate the crowsfoot error. Then you are only left with wrench error which most forget about as well!

 

On a smaller fastener it's not really a big deal. But on something like what was being mentioned with a 250 ft-lb torque spec, a 9% error can mean snapping a fastener or over stretching one that is already designed to be 75% of yield at working loads.

 

My example of the crowsfoot was that it in the most BENIGN set of circumstances introduces an almost 3% error!

 

It's something many people never realize. Imagine using a larger crowsfoot with a longer fulcrum! Or any number of circumstances that can introduce error into the equation.:mrgreen:

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  • 7 years later...
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youll want a decent torque wrench in fact you really should have two,


THIS  BEAM STYLE TORQUE WRENCH IS THE TYPE TORQUE WRENCH YOU WANT TO CHECK ROTATIONAL RESISTANCE 

beam_torque_wrench.jpg

BUT NOT WHAT YOULL USE TO TIGHTEN HEAD BOLTS

 


HUSKY $88 (worked rather well, over all I was pleased)


 FOR HEAD BOLTS AND MAIN CAP STUDS ETC.

torquewrench.png

torqueingr.jpg

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