nut & bolt tips
Posted: Thu Sep 02, 2010 2:55 pm
Hey Hatzers.
I found this online by chance and thought some others might find it useful too.
Nick
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."
I found this online by chance and thought some others might find it useful too.
Nick
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."