Date:         Sat, 16 Jul 2005 09:23:59 EDT
Reply-To:     THX0001@AOL.COM
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         George Goff <THX0001@AOL.COM>
Subject:      Re: lug nut torque?
Comments: To: wil@CHARMFX.COM
Content-Type: text/plain; charset="US-ASCII"

In a message dated 7/15/05 1:50:43 PM, wil@CHARMFX.COM writes:

<< I'll be getting some anti-seize and treating all the lugs and reinstalling
to spec next time I'm working on things. >>

Tightening a threaded fastener places it in tension.  The amount of tension
is gauged by how much the fastener stretches; this is called "bolt stretch".
The reason for measuring the amount of torque applied when tightening a
fastener is that the amount of tightening torque can predict the amount of bolt
stretch.  In reality, torquing a fastener is an uncertain way, for many reasons, of
determining how "tight" it is.  Using lubricants or anti-seize on a fastener
greatly changes the torque value required to
arrive at any particular amount of bolt stretch.  If you are planning to use
anti-seize on your lug nuts, consult the manufacturer of the anti-seize to
find out how much to derate the torque value.  I wouldn't be surprised if it is
30% - 40% less whenever anti-seize is used.

As an example, after applying anti-seize to the studs, the reactor head nuts
on a commercial power plant reactor are only tightened hand-tight.  These
studs are perhaps a foot in diameter; the anti-seize is in gallons and is painted
on with four inch wide brushes.  Of course, before the hand-tightening a
monstrous pretensioning device throws in a little bolt stretch.