Can nylock nuts be reused???

["Rich Hirsch" <rhirsch@domain.elided>]

> ... I installed mine with all of the bolt heads forward. I recall now
using
> the old standard of "when in doubt, bolt heads go up, forward or inboard"
> but in reality, unless there is some clearance or access issue involved,
> I don't think it's going to matter much.

> ... I also used all new lock nuts, which is recommended as
> nylocks are not designed to be reused.

In Carroll Smith's book, "Nuts, Bolts, Fasteners and Plumbing Handbook",
p.97, section "Rules of Threaded Fastener Use", he discusses these ideas:

<when in doubt, bolt heads go up, forward or inboard>

"Myth: Bolts must always be installed with the bolt head up and facing
forward so
that, if the nut should fall off, gravity and the force of the airstream
will tend
to keep the bolt in place. There is nothing wrong with installing bolts in
this
manner. In fact, in the interest of standardization, I usually do. But to
hope
that gravity or air pressure will keep a bolt in place is unrealistic. There
is
a place in this world for dreamers-but that place is not in engineering.
Neither
is it anywhere near an airfield or a racetrack. There is absolutely nothing
wrong
with installing bolts wrong end up or backwards, when it is more convenient
to do so."

<nylocks are not designed to be reused>

"Myth: Elastic stop nuts are single use items. If reused, they will not lock
reliably.
This one started in the infancy of the elastic stop nut when the locking
collar was made
from organic fiber rather than nylon and it wasn't particularly reusable.
Those days
have been gone for a long time. Any of the current families of self-locking
nuts can be
reused many times."

"In most applications the rule of thumb is: If there is no visible damage to
the thread
and you cannot spin the nut with your fingers, it is OK to reuse it.
Obviously this is
not true in the case of critical tension applications which require high
tensile nuts.
I do not reuse critical nuts, locking or not. In my world this includes all
connecting
rod and most cylinder head and main bearing cap nuts."

"Myth: Always turn the nut, never the bolt.Again, it is easy to see where
this one
comes from, and again, it is good practice. We have seen that bolts loaded
in shear
should be installed in close tolerance reamed holes. When we turn the bolt
in a
closely fitting hole, we will produce friction between the bolt and the hole
surfaces which can give a false tightening torque reading; damage the bolt
surface,
the hole surface or both; enlarge the hole; remove some of the plating from
the bolt;
and if the bolt happens to be made of titanium, the bolt will gall and weld
itself to
the wall of the hole."

"The trouble is that there are many applications where it is easier to turn
the bolt
than it is to turn the nut. Some books state that, since we don't worry
about turning
tension bolts installed in blind holes, we don't need to worry about turning
any bolt
when it is more convenient to do so. Wrong! What is being overlooked is that
tension
bolts are properly installed in loose drilled holes where there will be
little if any
contact between the bore of the hole and the shank of the bolt. My rule is
that
convenience takes a back seat to damaging parts; I turn the nut whenever it
is
possible to do so. However, a primary rule of life is that we do what we
have to
do-and that includes turning bolts and holding nuts when the need arises."

Rich Hirsch
St Louis, MO
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