On Sat, 19 Jun 2004 21:31:54 -0400, Glenn Ashmore
wrote:

Has anyone ever had any experience with or heard of a Nyloc nylon lined
nut backing off a bolt?
snip
Now the problem. A New Zealand sailor is claiming that his anchor
(which thankfully I did not sell) failed because the nut backed
completely off the bolt which allowed the bolt to fall out. There is
very little vibration and no torque on the bolt. The nut was in good
condition, new when installed and had never been removed. Is there any
way that a Nyloc nut in good condition could possibly make more than 20
turns on a loose bolt on its own?

Was the anchor set, or was the anchor in the boat?
If there was some sort of repetitive motion where
the shank continually rotated the bolt, it might
have backed the bolt out of the nut. Nylock (or
nylock type) nuts don't have a tremendous amount
of torque resistance -- just enough that they
don't turn easily. I can't quite turn one with
my fingers, but can turn them easily with any
kind of driver including a bare socket (no
drive). There is a reason why moused or safety-
wired pins are traditional in ground tackle.