Bolts, bolts, bolts

Jim

Jim
Joined
Mar 24, 2004
Messages
157
Location
Kingston, ON
Aircraft
Christavia
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:

https://shopswarf.orcon.net.nz/boltid.htm
https://www.sizes.com/tools/bolts_SAEtork.htm
https://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
 
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"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.
 
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.
 
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 :)
 
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
 
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.
 
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.
 
Jazzenjohn said:
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
 
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.
 
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.
 
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...
 
Just Kidding !!!
 
Here's a scan from my copy of 'Modern Metalworking' describing modern bolt manufacturing.

Far more efficient than cutting threads by hand.
 

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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!
 
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.
 
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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.
 
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 .

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
 
Udi said:
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?
 
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