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RE: Torque vs. Tension in Bolts

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My own experience is that it is pretty easy to rent or borrow a meter that
will allow you to gauge the tension in a specific set of bolts using the
"turn-of-the-nut method." Outside of direct tension indicators,
turn-of-the-nut is the most accurate way to determine bolt tension IMO.

> -----Original Message-----
> From: Christopher Wright [mailto:chrisw(--nospam--at)]
> Sent: Wednesday, July 14, 1999 8:50 AM
> To: SEAOC Newsletter
> Subject: Re: Torque vs. Tension in Bolts
> >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)        | this distance"   (last words of Gen.
> ___________________________| John Sedgwick, Spotsylvania 1864)