Bolts, bolts, bolts

[Jim]

With this I am probably putting my head in a hornet’s nest. :eek: So be it.... :) :)

In response to Don Law, some of our forum members reacted very strong against his use of grade 8 bolts. Personally I felt that he was bullied. Furthermore: I am not convinced that AN bolts are that much better than grade eights for a number of reasons. At times ANs may even be weaker:


1. Both AN and grade 8ths have adequate strength:AN bolts have a tensile strength of 125,000 psi and shear strength of 76,000 psi. That translates that a 1/4 AN bolt has a strength of: 3732 lbs in sheer and 6138 lbs in tensile. When we use 4 such bolts in a cluster as in Don’s ship, the total sheer strength will be 14 800 lbs. AN bolts are usually grade 5, while grade 8ths are even stronger. When are we ever going to stretch a single seat giro above the limit of 14 800 lbs??

The argument has been made that grade 8ths are harder and therefore more brittle and cannot take the bending moments put on it. That is true. But will they break? Again I am not convinced: With such massive strength the breaking point must be far above the forces that our machines gives.

The aluminum of our machines will probably give long before the bolts do....


2. As a first witness I call Chuck Beaty. The following conversation appeared on Norm’s old forum in April 2003
Eric Ruttan asked: I know Mr Beaty and others have stated that Grade 8 is better than AN for our uses.

I found a few posts in the old forum, but these didn't have references.(Other than chucks word, which counts)

Could someone post a reference so I might evaluate the evidence for myself and refer others to it.

Thanks
Eric
Chuck Beaty responded:
Eric, a quick Google search yields the following:

http://shopswarf.orcon.net.nz/boltid.htm
http://www.sizes.com/tools/bolts_SAEtork.htm
http://www.aeroparts.com.au/aircraft_bolts_from_aeroparts.htm

There are very few bolts still manufactured in this country, so it's a given that nearly all are counterfeit; AN or SAE.

An AN bolt is the equivalent of a grade 5 except for thread/grip lengths.

CA Beaty

Udi then asked:
For which parts of the gyro are AN bolts not strong enough? I am replacing most of the bolts on my gyro, including the "Jesus Bolt". All are AN-type bolts. Should I get stronger bolts?

Udi-
To which Chuck responded:
AN bolts are fine, Udi. But how do you tell if it's genuine or fake?

The more expensive a bolt, the more likely it's a fake manufactured by the Hu Flung Dung Ironworks in the Peoples Republic of China. Same idea as currency counterfeiters not wasting time printing $1 bills.

Fasco is an old line bolt manufacturer with plants in Mexico. Their grade 8 bolts can be identified by a coined triangle on the bolt head.

The problem with grade 8 bolts is that the threaded portion is too long and you have to drill the cotter pin hole.
C.A. Beaty

Udi responded: I guess I was naive enough to think that if I buy the bolts from a "real" aviation supplier, like Aircraft Spruce, than the bolts I am getting are certified mil-spec AN bolts...

Chuck answered: The problem, Udi, is that there is no certification agency for AN bolts. The FAA has never maintained source control for bolts.

Up until the time the US military discontinued the use of AN bolts, the Defense Department had provided source inspection. But they quit about 30 years ago and disposed of their then existing stocks as surplus.
C.A. Beaty

Mike Gaspard then mentioned a fact that concerns me a great deal:[/B] Not long ago I purchased a bunch of AN bolts from Wick's, and fully half of the bolt had an 'X' stamped into the heads rather than having a raised mark on them. I called to return them, and the salesperson I spoke to tried to convince me that they were real AN bolts, but I requested a refund. After a little hem-hawing around, they finally refunded my money.

I now just purchase them locally. They may still be counterfeit, but at least they're counterfeiting the markings correctly.
Mike Gaspard

Rightfully Chuck answered: I don't know that there is any authority that states SAE grade 5 is equal AN bolts, Eric. I was simply going by published strength characteristics.
And certainly if loaded in shear, you never want the load to be applied to the threaded area of any bolt. For tension loads, it makes little difference.

And Mike, if the "X" is cut with a chisel, most likely your "AN" bolt was manufactured in Bangladesh or some such place. The Chinese Communists appear to have modern bolt making machinery.

Genuine AN bolts must also have the manufacturer's logo coined in the head; CS (Cleveland Screw), Aero Supply, etc. That's not to say a known manufacturer's logo is sure proof it's not counterfeit but it's less likely.

I once saw a Discovery Channel program about a bolt making operation in Nigeria. The workmen were hand forging bolts from iron salvaged from junk automobiles, heating the lumps of iron in a charcoal furnace. Those guys were good. They could make a fairly decent looking hex head with nothing more than a hammer and anvil. But you might not want to use one of their bolts in critical areas of your flying machine.
C.A. Beaty

3. As second witness I call on Jukka Tervamaki.
His name has appeared frequently in the gyro community. Jukka’s fine designs later laid the foundation for the Magni line of autogiros. Looking at his plans, I see that Jukka used metric grade 8 bolts throughout his design. Not one AN bolt is specified anywhere in his designs, not even in the rotor head. Looking at this I wonder if the European Magnis use any AN bolts! :confused: :confused: Maybe our European friends can tell us!

To conclude: Although I am using aircraft-quality hardware, I am also convinced that grade 8 bolts from a reputable source will be fine. As Mike Gaspard and Chuck pointed out, some AN bolts may be sub-standard!

When using grade 8ths with aluminum one has to be very sure about the finish — that dissimilar metals do not interact.

'nuff said! :) :)

Jim

[mikezcnc]

"When using grade 8ths with aluminum one has to be very sure about the finish — that dissimilar metals do not interact."-- what does that mean? We all know that dissimilar metals do generate electric current but how can you prevent that on an aluminum frame using steel or stainless bolts? To comply with the rule of not using dissimilar metals one would have to use aluminum bolts because even using aluminum washers woulds prevent a physical cell from being active.

[skyguynca]

I agree Jim, I have used and still use some Grade 8 bolts on my machines. In most instances you are correct, the aluminum part will fail long before the bolt. Alot of people say that AN bolts bend before they break, well most bolts are in shear and properly torqued they won't bend, the aluminum will give first elongating the hole so the difference between Grade 8 and An is not important. I also work at the primary mechanic taking care of 2 Dehavlilland Twin Otters, 2 King Air 65A90's, 1 Beech 99 Airliner, a P51 and a Stearman, all with AN hardware and doing everything by the book on them. I get counterfiet hardward from our suppliers all the time, it has chiseld marking on the head not cast markings. The suppliers never ever take them back either stating that is they are geniune. Well chiseld markings are not done on any bolts I have ever seen in 20+ years in this business. For certified only AN because the law requires it, for my personal Grade 8 for it is stronger in most applications.

[Harry_S.]

My only complaint with AN vs Gr 8 is that the nuts seem to strip on the Gr 8 more easily than the AN hardware. Recommended torque is used on both bolts. I make reference to more than one torque application.


Cheers :)

[Brian Jackson]

Pardon my intrusion, but from everything I've read and studied, Army-Navy hardware was designed to be slightly softer to allow some flex without work-hardening or being brittle. The rolled threads VS. the cut ones posess greater pull-force (not tensile strength) because the crystalline structure of the molecules are constricted and still linear (like an hour glass), rather than being cut away. I believe this has a direct bearing on thread stripping and strength.

This is only what I've learned, so keep in mind I'm not speaking from experience.

Respectfully,
Brian Jackson

[Jazzenjohn]

Brian, it's unlikely you've ever even seen a cut threat bolt. I don't know who's floating the rumor that there are a bunch of cut thread bolts out there but for all practical purposes All bolt threads are Rolled. Cutting them is far slower and labor intensive so it's simply not done. If I cut a thread on the lathe I can make a thread that outperforms some rolled threads by cutting them to a closer fit (the h number sometimes listed after the size) but it's time consuming and rarely necessary. AN hardware is more corrosion resistant, usually has a better form for the uses gyro pilots have (longer shank and shorter thread). My opinions/knowledge about bolts come from being a Tradesman for 15 years, but not with aircraft, and I would defer to an AP mechanic. Skyguynca says pretty much the same thing. I've seen the P-51 he maintains( Beautiful!!), flown in the Twin Otters, Beech, DC-3 (years ago) and jumped from them. (never landed in one of them though). If he says they're OK to use I would be extreemly hesitant to disagree with someone with that level of Real, Practical, Actual experience.

[Not Yet]

I have never seen a grade 8 that didn't have rolled threads. I have seen some very inferior rolled threads, that were not as strong as a cut thread. The thread was actually hollow for the top 1/3 of the thread.

[Brian Jackson]

Brian, it's unlikely you've ever even seen a cut threat bolt. I don't know who's floating the rumor that there are a bunch of cut thread bolts out there but for all practical purposes All bolt threads are Rolled. Cutting them is far slower and labor intensive so it's simply not done. If I cut a thread on the lathe I can make a thread that outperforms some rolled threads by cutting them to a closer fit (the h number sometimes listed after the size) but it's time consuming and rarely necessary. AN hardware is more corrosion resistant, usually has a better form for the uses gyro pilots have (longer shank and shorter thread). My opinions/knowledge about bolts come from being a Tradesman for 15 years, but not with aircraft, and I would defer to an AP mechanic. Skyguynca says pretty much the same thing. I've seen the P-51 he maintains( Beautiful!!), flown in the Twin Otters, Beech, DC-3 (years ago) and jumped from them. (never landed in one of them though). If he says they're OK to use I would be extreemly hesitant to disagree with someone with that level of Real, Practical, Actual experience.
John,
Good info. I didn't know that. There have been other threads on this topic here which my education is limited to. I was simply conveying what I've learned of the subject here.

Thanks,
Brian

[Jazzenjohn]

Sorry if I seemed short Brian, I've seen other threads and wanted to stop this "cut thread" rumor before it became repeated so much it becomes fact.

[skyguynca]

Awww thanks John, hey did you see the P-51 lately???? last year I put the gun ports back on and cut fake barrels to put in them.....Bill even asked if I could put little red lights in them so he could play dog fighting.

[Jazzenjohn]

No, I haven't seen it recently. I did hear a rumor that Bill wanted to paint Cathy black to match all his other stuff...

[Jazzenjohn]

Just Kidding !!!

[gyromike]

Here's a scan from my copy of 'Modern Metalworking' describing modern bolt manufacturing.

Far more efficient than cutting threads by hand.

[skyguynca]

lol... watch out he just might

[REDHORSE556CES]

Found this on the Gizmologists web-site. I don't know if it will be of any help.

http://www.boltscience.com/

http://www.gizmology.net/nutsbolts.htm

[Dean_Dolph]

I've said it before and I'll say it again; anyone that is interested in practical use of bolts will get their hands on Carroll Smith's 'Nuts, Bolts, Fasteners and Plumbing Handbook'. Once you have it you won't have to ask any more questions on the subject!

[assiegordon]

One just have to assure that the SAE grd 8 bolts being used are not 'raw' stock, but plated. The bolts are plated with cobalt, which is closer to aluminum in electron valance, with less chance of galvanic corrosion. (The bolts are yellow, instead of the silver or black colour of an unplated bolt).

Actually, if you look in the EAA book on exceptable practices, there is a diagram showing bolt heads that are acceptable for use in aircraft. Although not mentioned, one of the heads indicated is an SAE grd 8.

James.

[et3dotcom]

Considering the fact that most of us do not have the ability to verify the source of bolts, and the material used to make them, is it not a good idea to apply some prudent tests? It is easy to load test bolts, and one can also magnaflux them (also easy to do your self). Also, a good idea to Zyglow aluminum with florescent dye and a black light to look for cracks prior to using aluminum in a critical area. Regardless of the source of materials, it makes sense to test them to make sure the assembly will be able to do the intended job – preserve your life!

Buying AN (or NAS) style bolts is good practice, as they are available in a wide array of lengths and grip ranges, ad they are drilled. Buying bolts that are precicly the correct size is much lower cost than cutting and drilling common bolts. If a grade 8 (or grade 5) is just right for the job – there is nothing wrong with using it. REGUARDLESS of what type of bolts and nuts you use TEST THEM to confirm suitability.

[Udi]

Personally, I would stick with AN bolts. I have done some research since I had the discussion with C Beaty Jim has quoted above, and I have come to the conclusion that the real question is not which bolt is stronger, but which bolt you can trust.

I don't buy all the hype about fake AN bolts. Bolts are traceable to the original manufacturer - as long as you buy them from a reputable aircraft hardware supplier. Don’t buy you’re AN bolts on eBay. If the bolt is in critical application, ask for a certificate of origin. By FAA rules, all AN hardware has to be traceable back to the original manufacturer. This will usually cost you some money, but you can trace the bolt back to the manufacturer. AN bolt manufacturers are not audited on a regular basis by the FAA but if a plane went down and the cause was determined to be a sub-par bolt, you bet they will trace it back to the manufacturer. If you make and sell AN bolts you better make sure you follow the standard to the letter.

If the markings on the bolt are suspicious, go to the USPTO web site and find the bolt manufacturer insignia. The USPTO web site is here (http://www.uspto.gov/web/offices/tac/fqa/active.pdf) .

I agree that grade 8 bolts may most likely be fine, but I personally feel more warm and fuzzy using bolts that I know were manufactured according to quality control procedures that are appropriate to life critical applications, and not for automobiles and trucks.

Udi

[et3dotcom]

I agree that grade 8 bolts may most likely be fine, but I personally feel more warm and fuzzy using bolts that I know were manufactured according to quality control procedures that are appropriate to life critical applications, and not for automobiles and trucks.

Udi

I had a wakeup call about 20 years ago when I lived in Colorado. I had an old one ton truck that I had been hauling wood out of the mountains with. I was on my way down a fairly scary road when I noticed a squeal on left hand curves. When I got home, I parked the truck after unloading the firewood. About a month later, I had some time free and decided to pull the wheel to check the bearing. I got in the truck to back it into the shop to use the air wrench and floor jack. About half way across the yard, the front passenger side wheel fell off! Plenty of life critical applications of fasteners in cars and trucks - 40k die each year in car crashes. Ever consider what it would be like if axle nut parted at 80mph?

[Udi]

Plenty of life critical applications of fasteners in cars and trucks - 40k die each year in car crashes. Ever consider what it would be like if axle nut parted at 80mph?
So, Daryl, are you saying that hardware store fasteners have the same level of quality control that AN hardware does? The facts that your front wheel fell of and that 40K die each year in car crashes do not make me any more warm and fuzzy about hardware store fasteners. I have been working in a manufacturing environment for many years and I know the value, and the cost, of rigid quality control standards.

Udi

[skyguynca]

Well after seeing a few hundred bad AN nuts with no threads, bolts with no threads, and yes counterfiet bolts (just call your local FAA office they will tell you that yes it is a real problem) that I have learned you don't use any hardware without a very through inspection of it regardless of AN or Grade 8. I only buy my Grade 8 from a very reputable dealer, just like my AN hardware, not from just the local hardware store. To blindly repeat rumors like the cut thread one is foolish, but those of us in the business and see it everyday know the truth, yes there is alot of fake an bolts out there, yes there are badly made AN hardware, no there is no real traceablity that is such a load of crap!!!!!!!!!!! You get no paperwork with hardware, none, zip, nadda......no matter who you order it from. The spar bolts that I have to replace in our Beech King Airs and Beech 99 have to be done every 5 years and they come with NO PAPER WORK and they come from Beech..oops I should say Raytheon because they do all the Beech parts, anyway there is no traceablity for bolts, just major components that are new or overhauled.

[Udi]

David, if you are done throwing this tantrum you may want to refocus and think about what you are saying. I am sure you have a copy of the FAA guidelines for acceptable hardware - why don't you open it and tell us what the FAA is saying about traceability. If you have no clue what I am talking about (which I suspect you don't), I will give you a hint: AC43.13-1B section 7 section 3.

Udi

[et3dotcom]

So, Daryl, are you saying that hardware store fasteners have the same level of quality control that AN hardware does? The facts that your front wheel fell of and that 40K die each year in car crashes do not make me any more warm and fuzzy about hardware store fasteners. I have been working in a manufacturing environment for many years and I know the value, and the cost, of rigid quality control standards.

Udi


Udi

I am not advocating the practice of using hardware store bolts on aircraft, or on cars designed to use special fasteners. I was only pointing out that any fastener type can be safely used according to it’s limitations and properties. FYI, many automotive fasteners are highly engineered – more so than AN standards mandate; in this case substitution a AN fastener for OEM automotive fasteners could result in a fatal failure.

My point is that we trust our lives to many non-AN fasteners in everyday life. There is nothing magic about AN, and aircraft could be designed to be held together with lead rivets, yet this would not be a wise choice for weight considerations. I agree that if an aircraft is designed to use AN fasteners – then it is usually better to use them than to substitute something else that may be under designed (or over designed). BTW, I do not substitute hardware store fasteners for OEM on my car. 100% inspection, and load testing to design limits is prudent regardless of what fasteners we choose to use on our experimental aircraft.

[Udi]

Daryl,

I totally agree with your last post. I would not hesitate using a grade 8 bolt in place of an AN bolt if I knew where it came from and to what standard it was manufactured.

Udi

[skyguynca]

I not throwing a fit, just stating facts. We order hardware here in orders of 25, 50 and 100 from Aviall, they are one of the largest hardware and parts people in the USA. Bolts, nuts, washer and cotter keys all come in a individual bag with the part number and that is all. No series, serial or batch numbers. IF you call Aviall they can only give you the suppliers identifier. You can read the FAR's all you want, I have read them several times and frequently (weekly) basis deal with our FAA Maintenance Director in our region because we have lease planes working for hire in Canada, so yes I do know what the regs say. Aside from the throwing a fit statement your reference to a FAR does nothing to show you have ever bought hardware, for if you had you would know the required tracing information is not given with the part and the end supplier only has to track who they bought so many items from. Batch tracing is not required. For that to happen every bolt, washer, nut and cotter key would need a serial number. That is why the FAA reps check in with us and other FBO's updating us on the number, kind and identifications of counterfit parts and hardware. IT is a real and very very serious problem we have had to deal with on several occasions. Yes Aviall has, but not their fault, supplied bogus bolts. We sent pictures of the bags showing their part number lables and the bolts heads which had stamped identification that was inaccurate and wrong. They gladly replaced them and we turned the bolts over to the FAA as requried. Now, unlike you I won't throw insults I will just leave it at a explination of information not a insult of intelligence.

[skyguynca]

Oh and just so you know the paragraph you are referring to states "you should only use bolts that have tracability to their manufacturing process"...."the head should show the stamp identifying the materials process and sometimes the manufacture" all that means is that the bolt might show who made it, but it should atleast show what it is made from and the part about tracablility says "you should" that doesn't mean you get proof when you buy a bolt, it just means buy from a reputable business or seller.

And we really should educate so here is a small lesson:

AC 43 Acceptable Methods and Practices
AC- Advisor Circular, it is not law just advice
AC 43 is the standard practices for repairs, modifications and materials, you don't have to go by it but if you do it makes life easier. I personally have done over 500 modifications and repairs that are not in the AC 43 13B, I have to draw them out on a form called the 337 Major Repair and Modications. Then I send it to the local FISDO who may elect to come out and look at the modification or repair or my just sign it depending on what it is. I have never had one not approved.

AD - Airworthyness Directive............law and must be complied with, you can even suffer criminal charges by not complying with it.

FAR - Federal Aviation Regulations, yes they are law but allow exceptions, you just have to file the proper paperwork.

Hope this helps UDI

[Udi]

David - my comment re-tantrum was not in response to the substance of your reply but because of the unprofessional way you responded to my post. I have no desire to get into a pissing contest, but since you have said that I have never bought any hardware, I am attaching a copy of a receipt, AND a certificate of origin for an AN8 bolt I bought for my AC. I have never said the law requires the traceability of bolts, all I said was that AN bolts are traceable back to the manufacturer! Go back and read my post. As you can see in the attached form, Wicks have sent me the information I needed to trace the Jesus bolt back to the manufacturer, including lot number.

Udi

[skyguynca]

That is great they send you a copy of a PO but that does not signify nor prove tracability, it just shows where they bought some bolts. Tracability comes with a tag for certification, for overhauled parts or new parts it is a 8130-? depending on its class and approval. Small parts from manufactures that are processed in quantity such as pulley brackets (just a example) are manufactured in large quanties hence the whole lot (100 to 1000+) will be on the same 8130-3 tag but each part will also carry a permenant ink stamp with the 8130-3 number and the manufacture symbol so this part can be traced back to the manufacture and the lot. Only on some very special close tolerance bolts and special order bolts do you see this stamp also. If the distributor or seller is giving true tracability they will send you or provide with the part the copy of the 8130-3 for the lot of the new hardware. This is very very seldom done and we have even had to pay $25 for a copy of the tag for Ministry of Transportation requirements for our aircraft in Canada to prove we did indeed change out the spar bolts on the King Air's because these bolts do not carry the ink stamp for tracability. The 8130-3 shows the components complete requirement for release and airworthyness and lot and manufacture. That is the only way to provid tracability, a copy of a purchase orders won't do for the FAA or in court. Because of law suits that is why Aircraft Spruce and Specialty, Wicks (which I think is the best for building supplies) even Aviall does not provide a 8130-3 for hardware, carpet, upolsty, seals, weather stripping or other mass produced parts unless you are willing to pay the fee. It then in the case of a accident or the aggravation of the situation that may have caused the accident shows responsibility back to them, then they must prove who they received it from,,,,,and so on and so on.... that is why they charge for it, it is a paper trail but not for free. Oh and you can really find all this info under Order 8110 and 8120 and of course the instructions for airworthness release 8130

[Papa Smurf]

Just a few comments on bolts. I have performed thousands of failure analysis on many different machines, components, etc over the last thirty years. I have encountered very few truly defective bolts. The most common bolt related failure is a result of improper installation. Second is improper substitution; grade 5 or even grade 3 were a grade 8 should have been used. Also, a lot of folks do not look at grip length when selecting a bolt. This is even true on though bolts. There are a few issues from time to time with metric vs. standard sizes. The bolt must fit the part. This takes my rambling mind to another common installation problem. Slotted holes and flat washers. Be careful how you use them. Make the parts to fit, use proper washers, and properly torque them.

The use of AN bolt vs. Grade 8 or even Grade 5 depends on the installation. In most instances, a properly sized grade 8 will function in place of an AN bolt provided that all bolt dimensions are the same. IE: grip length, thread length, head type, etc. Nuts come in different grades also and you should always use hardened nuts with a grade 8 bolt. Never mix coating types between the nut and bolt. Oil /Phosphate vs. zinc chromate vs. stainless, etc. Always inspect your bolts. Did you get what you ordered? Did you receive them in good condition? I’ve seen a few times were some warehouse person shipped bolts that were close, real close, but grip length went unnoticed and proper stretch could not be achieved even though proper torque had been applied. Stretch is how a bolt stays tight and the reason we have a lot of different sizes and placements of bolts in structures. Sometimes this is just an after thought during the design or a byproduct of some other design requirement.

On gyros, there are not that many bolts so cost relative to the structure is minimal. A grade 8 bolt from Caterpillar, Lawson, Rockford, etc. will cost very near what a AN bolt will cost. Never use the ones you purchase by the pound at the farm supply on anything that must stay tight. In most cases you should use what the design calls for but if you plan to substitute look at the whole joint. Ask yourself why was this bolt chosen? Are there clearance issues? Special requirements? Just think before you grab a handful and install.

On counterfeit bolts, they are out there so beware. Never use a bolt with a chisel mark. There are too many good quality bolts available to accept a second or resold reject. The comments on tractability are correct. The bolts are only traceable back to a certain lot or time frame, usually the month of manufacture and possibly the plant if they are made at multiple locations.

[Brian Jackson]

Thank you, Ken. Great write-up and cautions.
Welcome to our forum!

Regards,
Brian Jackson

[Jim]

It seems as if people are still confused about grade 5 and 8 bolts. (Some say that grade 5's are better because grade 8's are too brittle.) The following article, written by a rocket engineer, working for Lockheed Martin disperses of this myth. See http://www.rockcrawler.com/techreports/fasteners/index.asp

I also like the observation that improper (almost always too low) torque reduces bolt strenght.

He also has a good table giving the tension and shear strenghts of bolts.

Jim

[Canadian Rhino]

One interesting side note, If a bolt is used in an application where it will be forced to bend, the grade 8 bolt will snap where the grade 5 will bend. ;)