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Aircraft Quality

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Jaybannist(at)cs.com
Guest

Posted: Sun Mar 02, 2008 6:33 pm Post subject: Aircraft Quality

I'm very curious.  What makes a bolt "aircraft quality"?  I've tried Google and Yahoo and have not gotten any REAL answer.  Just "always use aircraft quality."  If a Grade 8 bolt has the same tensile strength as an AN bolt, what makes the AN superior? Can someone fill me in?



Jay in Dallas 601XL N2630J "Lil Bruiser"

notsew_evets(at)frontiern
Guest

Posted: Sun Mar 02, 2008 6:46 pm Post subject: Aircraft Quality

What makes a "certified" aircraft safe ?

It has FAA seal of approval..



---

klr12(at)psu.edu
Guest

Posted: Sun Mar 02, 2008 7:35 pm Post subject: Aircraft Quality

Every AN bolt, nut, washer, etc has to meet the criteria for a mil spec 

and is QC'ed to that spec.  SAE grades, such as a grade 8's, has an 

inspection done on only a few in a batch. The ones that are not 

inspected are a crap shoot.

JohnDRead(at)aol.com
Guest

Posted: Sun Mar 02, 2008 8:32 pm Post subject: Aircraft Quality

It is to do with the accuracy with which the bolts and nuts are  manufactured, form of the thread etc. There is a small radii between the head  and the bolt shank that properly distributes the load on the head. The tensile  strength of the steel is only one characteristic. The standards are set by  the Army and Navy hence the AN part of the part number not the FAA.

  

 John  Read



Phone: 303-648-3261

Fax: 303-648-3262

Cell: 719-494-4567   

  In a message dated 3/2/2008 7:47:49 P.M. Mountain Standard Time,  notsew_evets(at)frontiernet.net writes:

 [quote]-->    Zenith-List message posted by: "steve"    <notsew_evets(at)frontiernet.net>



What makes a "certified" aircraft    safe ?

It has FAA seal of approval..



---

zenithlist(at)yahoo.com
Guest

Posted: Sun Mar 02, 2008 9:09 pm Post subject: Aircraft Quality

[quote][b]

mhilderbrand

Joined: 28 Sep 2006
Posts: 36

Posted: Mon Mar 03, 2008 1:13 am Post subject: Aircraft Quality

I know I am pee'ing in the wind since I have no validation for this, but I heard Grade 8 will snap at failure, and AN bolts will bend first...  ???   

 

Michael Hilderbrand



  [quote][b]

planecrazydld(at)yahoo.co
Guest

Posted: Mon Mar 03, 2008 3:20 am Post subject: Aircraft Quality

It is not necessarily better quality. About 10 years ago a flood of "bogus" "aircraft grade" hardware, AN, MS, NAS, NASM, BAC, showed up in the market and there were some failures that led to a very expensive testing and certification to fasteners in the supply chain. That is with fairly rigorous process and quality standards that "aircraft grade" hardware come burdened with.



Grade 8 bolts have a less rigorous pedigree requirement (in my opinion). Things like rolled threads, perpendicularity of the washer face under the head and the head itself, concentricity,  fillet geometry under the head, alloy, heat treatments, temper, coating/plating, are all controlled in "aircraft grade" hardware.



Using "aircraft grade" is expensive but gives the peace of mind that the joint will perform as designed.



Jaybannist(at)cs.com wrote:[quote] -->      [quote][b]

planecrazydld(at)yahoo.co
Guest

Posted: Mon Mar 03, 2008 11:35 am Post subject: Aircraft Quality

Grade 8 bolts are to be 150,000 psi tensile strength minimum. AN3-AN8 bolts are heat treated to 125,000 psi minimum tensile strength.



A lower strength bolt can indeed bend more before failure more readily than a higher strength bolt. Bolted joints require well designed choices of the fasteners, the plates being joined, service conditions, etc. Since the bolts are a relatively small cost in the total, for airframes, why consider using other?



This discussion started with reference to WW referring to Grade 8 bolts in the engine. The original and all subsequent GM test engines were built without AN, MS, or NAS bolts - shouldn't their hardware be suitable?



Michael Hilderbrand <m_hilderbrand(at)sbcglobal.net> wrote:[quote] Be a better friend, newshound, and  [quote][b]

amyvega2005(at)earthlink.
Guest

Posted: Mon Mar 03, 2008 12:08 pm Post subject: Aircraft Quality

keep in mind that one of the speculative reasons that 601 crashed 1.5 years ago with a wing falure waws that the guy bought the plane and replaced the wing spar bolt with local hardware store bolt.  is it fact I do not know however i know the AN bolts are cheap and that a good design can still fail due to pilot failure on shoddy work and short cuts.



Juan



--

dalemed

Joined: 25 Dec 2007
Posts: 46

Posted: Tue Mar 04, 2008 6:35 am Post subject: Re: Aircraft Quality

Don't forget the torque ratings on threaded fasteners! An over-tightened bolt will be a weak bolt!

_________________
Dale
Zenith Zodiac CH650

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