As far as the difference in torque specs for coated/uncoated/lubricated
fasteners, pulled out my text book from machine design ("Mechanical
Engineering Design" by Shigley and Mischke).
Torque required to reach a given preload can be estimated by the equation:
T=K*F*d
Where T is torque, K is a torque factor, F is the preload, and d is the
major diameter of the fastener. The values given for the torque factor (K)
are:
0.30 for nonplated black finish
0.20 for zinc-plated
0.18 for lubricated
0.16 for cadmium-plated
0.12 with Bowman Anti-Seize
0.09 with Bowman-Grip nuts
(The chart of torque factors was taken from Bowman Distribution, a fastener
manufacturer)
That gives an idea of the effects of coating and lube on the torque values,
just to muddy the water a little more.
Jason Sukey
----- Original Message -----
From: "mordy dunst/ gasket works" <gasket.works@verizon.net>
To: <fot@autox.team.net>
Sent: Tuesday, March 16, 2004 10:19 AM
Subject: Re: lube torqued fasteners?
> To add to some other confusion..
>
> With regard to aftermarket high quality fasteners i.e. ARP or other....
my
> understanding is that they may have a coating (anti rust or other?) on
them
> from the factory.
>
> I have been told that the clamping force and torque specs are different
if
> the fastener has a coating & lubricant vs. uncoated & lubricant vs. coated
&
> dry or lastly dry and uncoated.
>
> Since different manufacturers use different fastener coatings...I have
been
> told to wire brush the threads clean of any coating prior to application
and
> place them dry in our old design motors.
> M. Dunst
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