On our Triumphs there are some possible pitfalls to trying to torque "dry".
Unless you're using new nuts and bolts... getting the 30+ years of
gunk/assembly lube/WD-40 out of a part can be daunting. So do you figure on
using an "almost dry" torque figure?
And when you go to remove that part that was torqued dry then allowed to
collect rain/road dirt... Well, you get the picture.
At work there's a neat pocket reference that I meant to borrow today for
this discussion. It lists the tech specs for the different grades of bolts
(grade 2 through grade 8) with "normal" torque values for USS (coarse)
thread. SAE (fine) thread torques are "9% higher".
Then it lists a chart by diameter for lubed torque specs which are between
15% and 30% lower. With the caveat that the manufacturer should always be
consulted if there is a question of proper application.
If anyone is interested I can try to scan a .jpg of the relevant pages.
Cheers,
Jim
Dallas TX
britbits@tiu.net
-----Original Message-----
From: owner-fot@autox.team.net [mailto:owner-fot@autox.team.net] On Behalf
Of Randall Young
Sent: Wednesday, March 17, 2004 4:35 PM
To: fot@autox.team.net
Subject: RE: lube torqued fasteners?
> One time in the distant past, I was using STP as an assembly lub., and
> stripped some threads.
That's the thing that puzzles me about this whole thread (no pun intended)
... 'Dry' is clearly an easily repeatable condition, and at least for most
stock fasteners, is the way the original torque specs were given. It seems
to me that 'Lubricated' is a hugely variable condition depending on just
what you use for a lubricant. Even "motor oil" may be highly variable since
it's being loaded far beyond the pressures it's normally used at, which
means that different oils may behave quite differently ... as the example
above shows.
So, why guess at how good your lubrication is under the conditions at hand,
and then call that more accurate than using the specified (and repeatable)
condition ?
Several have mentioned 'sticktion' ... I was taught to always hit the torque
target with the fastener still turning so that sticktion is not an issue. If
you stop close enough to final torque that it isn't still moving when you
hit final torque, you have to back off and do it again.
Clearly this doesn't apply to things like ARP fasteners, where torque
figures are given in combination with a specific lubricant ... as long as
you use that specific lubricant.
Randall
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