

| Subject: | Re: lug nut torque? |
| From: | George Goff |
| Date: | Sat, 16 Jul 2005 09:23:59 EDT |
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.
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