<< > > > Robin wrote:
 > > >
 > > > Hello Paul,
 > >
 > > >     I hope this doesn't immediately sound like a dumb

question, but how

 > can you find out exactly what the particular specifications for

any given

 > "AN" part is?  For instance:  Metallurgist typically say there is just
about
 > no difference between an American made grade 8 bolt and an AN

bolt.  Well,

 > that's fine and dandy and we all can see that relationship pretty

well when

 > you're talking about common fasteners, but what happens when you

begin to

 > talk about other products?  How can you really make a sound

comparison?

snipped

Charlie Kuss wrote:

  At one time, I shared Robin's opinion regarding hardware.  There are

considerable

differences between a commercial grade 8 bolt (stronger, relatively

brittle) and a

common (not high strength) AN bolt. AN bolts are actually softer. They

are designed

to fail "gracefully". This means that rather than cracking or snapping

when over

loaded, they will stretch. A broken grade 5 commercial bolt (a closer

comparison to

the most common AN bolts) and a stretched AN bolt are both junk. The

difference is

that when the commercial hardware fails, it fails catastrophically. Part

of your

aircraft may fall off. (I hate when that happens) The AN hardware gives

you a chance

to get the craft back on the ground. Hopefully, you will find that it has

failed

during your next preflight. Of course, this nice feature is totally

useless IF you

don't do proper preflights and follow proper preventative maintenance

procedures.

 As you progress from grade 5 up to grades 7 & 8, the commercial bolts

are even more

likely to fail catastrophically, as they are even more brittle. Hi

strength AN

hardware is much less likely to fail in this manner. In short, AN

hardware provides

a certain "safety net". You ought to try reading FAA AC 41.13-1b  It is very
educational. I've learned a lot from it. As I learn more, I realize that

I knew and

still know a lot less than I thought I did.

  I'm sure that there are areas of each ship where you can safely substitute
commercial hardware for AN hardware. Please be careful that you don't use

commercial

hardware in flight critical areas. I don't want to read about anyone here

in the

NTSB accident reports.
Charlie Kuss
RV-8A fuselage   (better to study on the ground, than be tested in the air)
Boca Raton, Fl.

  I think you meant to say AC 43.13-1b, which I have repeatedly recommended
to all on this list that do not have it ( and2b).   I agree wholeheartedly
with your whole post, altho "soft" may be a bit imprecise in engineering
terms.  I would prefer "ductile",
but your explanation is right on. You want graceful failures and this is what
AN (all now MS) hardware is designed for.

Please take the opportunity to save your life by reading this excellent,
inexpensive
reference work.  My Dad got me my copy and it was a real education in the
details
of aircraft "craft" - and as Tracy says "the devil is in the details".  Most
of the
information in this cost somebody their life at one time or another to
learn.  Learn
it on the cheap.  Hopping off my soap box . . . . .

Bill Freeman

 
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