Gene Kearns wrote:
You said, "The engagement, or amount of material 'gripping' between
bolt & stud, will be approx twice as much. "

Oh, I thought you were objecting to the "less tendency to loosen due to
vibration" statement. That's out of the ASCME handbook too but right now
I don't have time to do a big web search. If you've read all the
references I posted then by now your knowledge is probably greater &
more up to date than mine.



The only reason the fastener might be stronger, in any way, is that
the minor diameter is greater on a fine threaded bolt than on a
coarse thread...

The difference in root diameter & major diameter, factored by how
closely the pitch is machined, determines how much of each thread is
engaged. Another factor is that for a given size bolt, the fine thread
will have more threads per unit length and this will act to multiply the
engaged length of thread. Plus, fine threads are usually machined to
closer tolerance.


.... this is, of course, countered by the fact that a
fine threaded bolt is easier to strip. Nearly all decent bolts will
strip before they break in tension.

That's not been my experience. Maybe i haven't been using "decent" bolts?




While there may be some minimal advantage to a fine threaded bolt not
backing out... this is minimized to the point of irrelevance by proper
fastener-locking technology.

Again, not true in my experience. I'd generally prefer to use double
bolts and antisieze than lock washers, self lockers, or Loc-Tite
(although it's truly marvelous stuff).

Fair Skies
Doug King

This is such an easy answer, I can't believe nobody has answered correctly.


You use a coarse thread bolt when the only nuts you have that match are
coarse thread.
You use fine thread bolts when the only nuts you have are fine thread.

You give up and head for the hardware store when one is metric and one is
standard and they are the only ones that will work for your project.


Eisboch (yeesh.... why is this so difficult?)

"Eisboch" wrote in message ...
This is such an easy answer, I can't believe nobody has answered correctly.


You use a coarse thread bolt when the only nuts you have that match are
coarse thread.
You use fine thread bolts when the only nuts you have are fine thread.

You give up and head for the hardware store when one is metric and one is
standard and they are the only ones that will work for your project.


Eisboch (yeesh.... why is this so difficult?)

Pretty much correct, except, even with a quite large bolt and nut bin,
I usually get tired of hunting after a few seconds, and head for the
hardware store anyway! One day, I hope to need a bolt, and actually
find the right one in my bucket!

basskisser wrote:

"Eisboch" wrote in message ...
This is such an easy answer, I can't believe nobody has answered correctly.


You use a coarse thread bolt when the only nuts you have that match are
coarse thread.
You use fine thread bolts when the only nuts you have are fine thread.

You give up and head for the hardware store when one is metric and one is
standard and they are the only ones that will work for your project.


Eisboch (yeesh.... why is this so difficult?)

Pretty much correct, except, even with a quite large bolt and nut bin,
I usually get tired of hunting after a few seconds, and head for the
hardware store anyway! One day, I hope to need a bolt, and actually
find the right one in my bucket!


When I was a lad, Connecticut was blessed with thousands of factories
turning out all sorts of goods, and, as a result, there were huge supply
distributors all around the state. West of my father's main store on the
Boston PostRoad was an industrial supplier called Roberts, Crozier and
Ballou, and they had every fastener known to mankind in virtually every
materials. Stainles, bronze, brass, iron, steel, galvanized, whatever.
They had it all. It was a wonderful place to visit. Equally
wonderful...the Western Electric Manufactuing facility about a mile from
my dad's store. If the guards knew you, they'd allow you to dumpster
dive. Many of my junior high and high school science projects began in a
Western Electric trash bin!

Gene Kearns wrote:
Personal favorites..... self locking nuts (elastic or all metal),
cotter pins, and safety wire.

If you use the self-locking nuts with plastic insert, you know you're
supposed to get a new one every time you take it off? And you're not
supposed to exceed a certain amount of excess thread? Other than that,
they're great...

As for the metal ones, the reason they work is by chewing into the
thread. The are either squashed out of round and then remachined to fit
the wrench size, or else cut slightly off standard. Either way you
have metal on metal galling as the lock mechanism.

But hey, I'm not trying to say there's anything wrong with that
Just explaining my own personal fetishes. Double nuts are a PITA to work
with. Locking wire is good when tight space, balance, or alignment isn't
an issue.


basskisser wrote:
Pretty much correct, except, even with a quite large bolt and nut bin,
I usually get tired of hunting after a few seconds, and head for the
hardware store anyway! One day, I hope to need a bolt, and actually
find the right one in my bucket!

This is a prime example of what a friend of mine calls our society's
pathological impatience. It would be quicker & cheaper to keep your
fasteners organized better, and even if you didn't you could find the
right one quicker than you can drive to the store (assuming it's really
there). What's the frikken hurry?

A story- once upon a time, my family lived on a rural property with a
barn. My father and I rapidly filled the barn with sports car & boat
parts, including several 55gal drums of various threaded fasteners from
many many sources. We would brag that there was at least one of
everything in there. It just so happened that I was rebuilding a 1966
Porsche engine in the barn and needed a very special bolt (left hand
custom thread with a long shank for the rocker bearing cover). I could
send off to Porsche Germany, which I had already done in the course of
this job, or hunt through the barrels.

I kicked over the first barrel and hunted through every single bolt in
it (a freind helped). No. We kicked over the second barrel, and about
3/4 of the way through we found two of the exact bolts, taped together
and still coated in cosmoline. A few months later I sold the second one
(which I had placed on our mantelpiece) to our local Porsche shop when
he needed one. I often wonder if anybody has been looking in those
barrels for that exact bolt since then....

Fair skies
Doug King

Harry Krause wrote in message ...
basskisser wrote:

"Eisboch" wrote in message ...
This is such an easy answer, I can't believe nobody has answered correctly.


You use a coarse thread bolt when the only nuts you have that match are
coarse thread.
You use fine thread bolts when the only nuts you have are fine thread.

You give up and head for the hardware store when one is metric and one is
standard and they are the only ones that will work for your project.


Eisboch (yeesh.... why is this so difficult?)

Pretty much correct, except, even with a quite large bolt and nut bin,
I usually get tired of hunting after a few seconds, and head for the
hardware store anyway! One day, I hope to need a bolt, and actually
find the right one in my bucket!


When I was a lad, Connecticut was blessed with thousands of factories
turning out all sorts of goods, and, as a result, there were huge supply
distributors all around the state. West of my father's main store on the
Boston PostRoad was an industrial supplier called Roberts, Crozier and
Ballou, and they had every fastener known to mankind in virtually every
materials. Stainles, bronze, brass, iron, steel, galvanized, whatever.
They had it all. It was a wonderful place to visit. Equally
wonderful...the Western Electric Manufactuing facility about a mile from
my dad's store. If the guards knew you, they'd allow you to dumpster
dive. Many of my junior high and high school science projects began in a
Western Electric trash bin!

My uncle was an aviation machinist, and where we lived, he ended up
working as the head mechanic at a local Westinghouse factory that made
lightbulbs. The machines that were there were quite complex, with
many, many parts and pieces. Our garage was full of that stuff, nuts
and bolts in english and metric, long before most people in the U.S.
knew what metric was.