Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

Re: Torque vs. Tension in Bolts

[Subject Prev][Subject Next][Thread Prev][Thread Next]
>Can someone tell me a rule-of-thumb formula or another method to convert
>the torque value placed on a bolt to the tension value. ...
>I do read, however, in the AISC Connections book that any
>published method of conversion is not acurate.
So long as you're happy with a method of conversion that isn't accurate, 
the relationship between torque and tension is T=kFd. T is the torque in 
in-lb, F is the bolt tension in pounds and d is the nominal bolt diameter 
in inches. The factor k is semi-empirical and commonly varies between 
0.12 and 0.2 depending on friction and manufacturing allowances. The 
higher value seems to be preferred in most of what I read. But as you 
said, it isn't real accurate. It's also based on elastic behavior and may 
not be suitable for LRFD adherents. ;->  

In machinery, bolts are tightened to 50-75% of their proof load to avoid 
fatigue failure. The corresponding tensile loads are high enough to crush 
soft materials like wood and plastic unless you use smaller bolts and 
consequently more of them. 

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