torque wrench inadequecy??

[Tony D]

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.

[grumpyvette]

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 

BUT NOT WHAT YOULL USE TO TIGHTEN HEAD BOLTS

 

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

http://www.homedepot.com/p/Husky-1-2-in-Click-Torque-Wrench-H2DTW/202916180?N=5yc1vZc6ev

 FOR HEAD BOLTS AND MAIN CAP STUDS ETC.