Bolts n Nuts

ElJay

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Hi. I intend to completely disassemble, clean and inspect a bensen I bought 2nd hand. It has been in storage 26 years.

Screws, nuts, springs, cables, cotterpins etc are ALL showing rust. Some a little more than others. Basically if it's steel, its rusty.
I want to replace it ALL as I go back together if for nothing else, peace of mind.

Some books, advice columns and others say to use "aircraft quality" only fasteners etc.

However the bensen manual says "materials specified for bensen in large part are of commercial quality and therefore inexpensive". Nowhere in the plans or material list does it call for "aircraft quality" nuts/bolts etc. (this does NOT include the structual parts, of course).

Aside from it being my b*** hangin out, what are ya'lls comments on using just plain old hardware store nuts/bolts/washers etc.???

I'm not opposed to either, other than aircraft quality is much more "EXPENSIVE". I'll spend the extra bucks if that is what ya'll say, but not just for the heck of it....
Thanks
LJ
 

gyronutt

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nuts&bolts

nuts&bolts

i think there's a bolt kit at ken brock's for the bensen?check it out!
 

Chuck Irby

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I would use all "AN" nuts, bolts and washers, but wouldn't have a real problem with grade 8. It's more than the balls, it's your life.
 

scottessex

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The tensile strength of comercial fasteners is suspect, Use only AN or NAS hardware.
A standard #10 or 3/16 bolt is no where near as strong. Plus AN and NAS bolts have rolled threads instead of cut threads.

Usually if something is aviation specific, it is for a reason, Remember, you can't just pull over when you hear something funny or when the muffler falls off. etc.
 

Brian Jackson

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ElJay said:
Aside from it being my b*** hangin out, what are ya'lls comments on using just plain old hardware store nuts/bolts/washers etc.???
DON'T! :eek: AN hardware is designed for specific tensile standards whereas Ace Hardware's "Oh-Let's Build-A-Patio" bin could be filled with anything that resembles a bolt. Spend the extra few bucks... after all, you mentioned in your post this was for "peace of mind." Don't skimp on the hardware.

Cheers,
Brian Jackson
 

Chuck Irby

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Scott, help me out hear, please. I have always been under the impression that "AN bolts" had a minimum tensile strength of 125,000 pounds, and "Grade 8" is 150,000 pounds. Am I correct? If so, why do you have a problem with grade 8 bolts? Is it that that they are not inspected as thoroughly as AN?
 

scottessex

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Most of the aircraft bolts are a closer tolerance, they don't have the zinc or cad flash buildup that comercial hardware has, Also the threaded area on the AN and NAS bolts is shorter, so less sticks through the nut.

Again, the aircraft hardware is less likely to have something substandard slip through the inspection process,
And I am not sure about the rolled threads, on grade 8. but rolled threads are much stronger.

If I can't find an aircraft spec bolt, then would use a high quality grade8, but that's just me. :)

I also don't build anything with nails, I always use screws, just me I guess. :p
 

Chuck Irby

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Thank you Scott. That makes sense to me. I have used a few grade 8 bolts and am pretty sure the threads are rolled. I am also pretty sure that they do have a higher strength than AN, but not NAS. It seems that the NAS are the stronger of the three.

ElJay, You can't go wrong with Scott's advice. He is an A&P. Too, be sure you understand that most hardware store bolts are only grade 2, and a few are grade 5.
 

scottessex

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Another thing, For the price, there is not much difference in cost for the AN and grade 8 , so it makes sense to go with the AN.
 

KenSandyEggo

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Price depends on the size. I have honker-sized (7.75") AN bolts on order for my prop. I believe 6 of them are around $125.00, or over $20 each. Grade-8s of the same size are $6.00 each. On smaller ones, the difference would probably not be as significant.

Question: When using 8s on a prop, isn't the shank taking all the stress from the rotation? The prop is basically pushing against the mounting plate, so I don't see tensile strength as an issue. Therefore whether the threads were cut or rolled would not be that significant as they're sticking out where there is no torquing stress. Is this assumption correct? Are grade-8s as strong as AN as to the shank of the bolt and rotational stresses? (I can't think of the word that's opposite of tensile strength). Plus, I have most of the 7.75" of shank immersed solidly in aluminum with the electric Ivo prop. I would think that this is a plus factor with all that shank taking the rotational stress.
 

scottessex

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Sure, you want your bolts properly torqued, and the shank is taking the load, but the threads keep it tight.
On a pusher instalation your prop bolts would be under shear stress, so tensile strength is not really important, What you are concerned with is shear stregnth. Or at what point the bolt shears in two from side loads, as opposed to tensile, where it is pulled until it breaks.
To not overly complicate things, Most aircraft hardware is fine thread , not all but most. If you go with grade 8 go with a fine thread. Most coarse thread applications a grade 8 is more than adequate. I used grade 8 coarse thread bolts to hold my engine on, I drilled holes in the heads for safety wire. Aluminum housings should always use coarse thread , unless you have a helicoil installed. Get the best you can afford.

Another advantage of AN is they are available in 1/32 graduations, making for less washer stacking, or having to cut the ends off bolts,
or having short shanked bolts where the threads cause wear against material etc.
I think grade 8 comes in either 1/4 or 1/2 inch graduations in length.
 

gyromike

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Ken,

It isn't the shear load on the bolts that keep the prop from moving around. The bolts clamp the prop between the prop flange and the crushplate (on a wood prop). The friction between the prop and the mounting flange keeps the prop from moving back and forth. The bolts are in tension the whole time.

Loosen the bolts enough where the prop can move due to the power pulses from the engine, and it can end up smoking from the friction. :eek:

That's why wood props should be checked for proper tourque on a regular basis. I use a stack of Belleville spring washers on my prop bolts to maintain pressure as the wood shrinks and swells due to humidity.
 

Doug Riley

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The issue with using Grade 8 hardware instead of AN is not the strength of (real) Grade 8's. The issue is that so many bolts marked Grade 8 are fakes.

Unfortunately, some "AN" bolts are fakes, too. The topic was discussed at great length on the old forum. There are a few manufacturers whose products are what they are marked to be. In the AN world, they'd include California Screw (CS), Rockwell and Aero. Real AN's have a RAISED (not indented) cross and the maker's initials on the head.

Bensen's hardware was AN. His stock numbers simply substituted "BA" for "AN." So if you are replacing an bolt called out as a BA4-13A on the plans, just get an AN4-13A.

If you don't have the plans, you can buy a little metal bolt guage that will quickly give you the right numbers. You just drop the old bolt into a slot and read the part# off a scale printed on the guage.

Buy aircraft hardware from a good supplier such as Wicks Aircraft or Aircraft Spruce. If you get a funky-looking bolt from them, request a replacement.
 

ElJay

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Big Spring, TX
A HUGE THANK YOU!! To all who responded and those that may, you have inspired me here. Terrific information and truly a "craftsman knows all" set of answers. I could hold a very healthy discussion on home appliance repairs, but for "design" stuff, I can only wonder. Thanks to ya'll I'll be much safer. That little knowledge jewel about the bensen numbers sub for the true an numbers was mind blowing....go figger. Yes I am fortunate that I do have the plans, so I can/will be able to get exact part for part....and I will purchase from a reputable dealer/seller. The kit sounds good, and I like to support "gang related" vendors....thanks again folks...can't wait!
LJ
 

barnstorm2

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I always order my nuts and bolts from Wicks or Aircraft Spruce. My somewhat related question is: what about safty wire? Is the general purpose wire from the local hardware store just as good as saftey wire from an aircraft supply shop?
 

Chuck Irby

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Hello Tim, I got the large spools of the two different sizes of wire when I got the twister. I have used hardware store wire on stuff around the house and barn and definitely have noticed a difference. So I always use the good stuff on the gyro.
 

Udi

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Doug Riley said:
...Unfortunately, some "AN" bolts are fakes, too. The topic was discussed at great length on the old forum. There are a few manufacturers whose products are what they are marked to be. In the AN world, they'd include California Screw (CS), Rockwell and Aero. Real AN's have a RAISED (not indented) cross and the maker's initials on the head...

When I bought a new spindle (Jesus) bolt for my Air Command, Aircraft Spruce did not have the right size and I bought it from Wicks. The bolt that arrived had no raised marks at all. It had an indented x on one side of the head and a manufacturer's code on the other side. Since this is one of the few live/die-type bolts on the gyro, needless to say I was a bit concerned.

I called Wicks and asked for a copy of the bolt certificate of origin. I also looked up the manufacturer's code that was stamped on the bolt and found that this manufacturer is here in the US. You may find the list of hardware insignia on the US Patent and Trademark website.

Although the manufacturing process of AN bolts is no longer supervised or audited by the US Air Force or the FAA, manufacturers that sell AN hardware are responsible for the quality of their products. Every piece of AN hardware that sells though a reputable supplier has a paper tail behind it - from the batch number that it was made in, to the retailer shelf.

The certificate that I received from Wicks for my spindle bolt told me the lot number that the bolt came from. In fact, when you buy AN hardware, the retailer is keeping a record of which box your bolt came out of. If you have an accident due to a failure of AN hardware, the NTSB can track that piece of hardware back to the manufacturer.

It may be true that some forged AN hardware is finding it's way into the US, but I doubt you would get any of it from a reputable supplier. If you are not sure, do your homework and track your hardware back to the manufacturer. But I don’t think this is a real concern – all the GA aircraft in this country is built and maintained with the same hardware that we buy at Aircraft Spruce at al, and I don't see them falling out of the sky.

Udi
 
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Brian Jackson

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Thanks, Udi, for that terrific write-up of AN documentation & tracking. I never knew that before. But I wonder how many builders actually request and maintain tracking information of critical AN hardware (teeter bolts, rotor spindles, etc.), or how the FAA would notify them in case of a questionable lot number should a defective bolt be both discovered and reported. Though my studio and check book balance are disaster areas by orders of magnitude, I'm keeping meticulous records of every facet of my GyroBee project, of which the critical bolt documentation will now be part. Now my only question is: Is Wicks in the habit of providing AN documentation upon request? Or is this out of the norm for most orders?

Thank you again for that great info and insight.

Respectfully,
Brian Jackson
 
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