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Re: BOLT TORQUE/TENSION RELATIONSHIP

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>1.  I need to tension an ASTM A490 bolt to a certain value (somewhat of a 
>hypothetical question).  I need to calculate the torque required to 
>achieve this tension.  Could someone tell me how to calculate the torque? 
The relationships are a little complicated to write up here. Get hold of 
a copy of Shigley's machine design text or a mechanical engineering 
handbook to explain all the caveats. You can go through the motions using 
<http://www.norbar-usa.com/ttc/. but if you don't know what you're doing 
you need to be very careful as there are a lot of judgement calls.  
<http://www.steelstructures.com/SBH/SBH%20torque.htm> is another web page 
with some information to get you started. If you don't understand the 
caveats you really ought to find someone who does.

>2.  Do I need to worry about pre-tension?  If yes, will pre-tension need 
>to be considered in the equation in item 1 above for calculating the torque?
You're already worrying about pre-tension--that's what torqing the bolt 
is supposed to provide. Give some serious thought to doing some in-depth 
reading about the subject before someone gets hurt...

Christopher Wright P.E.    |"They couldn't hit an elephant at
chrisw(--nospam--at)skypoint.com        | this distance"   (last words of Gen.
___________________________| John Sedgwick, Spotsylvania 1864)
http://www.skypoint.com/~chrisw



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