Jim
Jim
With this I am probably putting my head in a hornet’s nest. 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! 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
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! 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
Last edited: