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Re: [ST] copper grease and torque settings



The relationship between the longitudinal force and the rotational one
is going to be close to direct proportionality to the coefficient of
friction between the two (?) materials (bolt and what it screws into). 
Consequently, reducing the coefficient with a lubricant will increase
the longitudinal force (stretching the bolt) for a given torque
setting.

Conversely dirty threads (solidified Loctite or gasket sealant) will
reduce the compressing effect for a given torque.

Chris Harwood
00 RS

>>> stevenlawler@xxxxxxxxx 20/06/2007 20:14:54 >>>
In a previous email,  Kevin Dicks wrote:
> I have been told the total opposite - all torque settings are DRY. 
Adding
> anti-seize, while a good idea for dis-similar metals especially,
effectively
> acts as a lubricant so the appropriate torque settings need to be
reduced.

I actually saw this in a seminar on fasteners. The set up was a bolt 
going through a plate that read the compression pressure applied by 
tightening the nut to the proper torque. No anti-seize was used. The
nut 
was loosened then re-tightened to the proper torque. The reading was
now 
lower. This was done two more times and each time the pressure was less

than the previous time. Anti-seize was then applied and the nut 
re-tightened. The pressure was higher than the initial reading. I don't

know all the physics behind it but that is my story and I'm stickin' to
it!

-- 
Steve Lawler
Construction Coordinator
"Taking Chance"


"If there are no stupid questions, then what kind of questions do
stupid 
people ask? Do they get smart just in time to ask questions?"
             -- Scott Adams
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