[AX-O]

I asked the question "when is a rivet too old" on this forum not long ago. A few people said that rivets from 2004 were not too old to use. So I used them. Here is my kitlog entry discussing what happened.


I started the day very anxious due to all those platenuts that needed to be installed on the main spar. The day started slow and I was in good spirit. First thing was to spot prime all the countersunk holes. After that I riveted all the platenuts for the #6 and #8 screw holes on the left wing. I used the left over rivets from my tail kit because they were newer and they looked to be in better shape than the ones that showed up with the wing kit. I used the same rivets on the left wing as well until I ran out. Once I ran out of the newer rivets, I started using the older ones (look at the picture below, the gold rivet are newer than the silver looking ones). Why am I making such a big deal about the rivets you ask? Well I bought the wing kit from a guy that no longer wanted it. The kit was delivered to him late 2004. He just inventoried the wing kit. No work was started. After I finished riveting all the platenuts on the right wing, I checked the work. I saw that over HALF of the rivets that I installed (old ones) had hairline fractures. I almost cried. I knew how much work was ahead of me. I had to drill out every one of those rivets. All the old rivets that I had were discarded and I ordered over $100 worth of new rivets. Not so happy but rivets hold the airplane together. Kind of need good rivets. After I went inside, ate a peanut butter and jelly sandwich (my girlfriend made it because she saw had mad I was) and calmed down, I fabricated W-731 and riveted the K1000-4 platenuts to the spar (with rivets from the tail kit). Do yourself a favor, don't use old rivets.

 

[az_gila]

Questions

AX-O (huh?)

Can you please describe the nature of the cracks and how the rivets were installed?

I've been using 10+ year old rivets with no problems .... and yes, I do inspect them carefully.

Could it be somewhat related to your installation technique?
Could you describe some of the cracked ones as over-driven?
Did you use multiple hits (a long rivet gun burst) to install?
Did any squeezed ones crack?

Any others care to comment?

gil in Tucson

 

[Mel]

I'm afraid I have to agree with Gil. You may have gotten a bad "batch" of rivets. I have used rivets over 15 years old and never had a problem. And, yes, as an A&P, I do inspect them thoroughly.

 

[az_gila]

Update

Out of interest, I just checked the generic spec. for rivets...

NASM5764
RIVETS, STRUCTURAL, ALUMINUM ALLOY, TITANIUM COLUMBIUM ALLOY, GENERAL SPECIFICATION FOR

No mention of storage or age requirements for the "AD" rivets we use.

As Mel said, I think you got a bad batch.....

gil in Tucson

 

[Bob Axsom]

Me Too - no problem with old rivets

I would purge the "old" stock because they are bad not because they are old. It happens even in shipments of parts from approved suppliers with material certs. The application also can cause problems and the center portion of platenuts especially dimpled ones and floating ones require more care than regular structural riveting.

Bob Axsom

 

[AX-O]

Could it be somewhat related to your installation technique?
I don't think so. I used the same technique with all the rivets (old and new). I only saw the fractures on the old ones. I have been doing the same thing over and over with all the rivets.

Could you describe some of the cracked ones as over-driven?
All the rivets were squeeze with a pneumatic rivet squeezer and checked with the rivet gauge.

Did you use multiple hits (a long rivet gun burst) to install?
Only one squeeze

Did any squeezed ones crack?
All the old ones

May be, it was just a bad batch.

 

[AX-O]

Another question, why do rivets show up with a date on the bag if the date is not important?

 

[jcoloccia]

Probably so you can track them. I'd send an e-mail to Vans about it. If it really is a bad batch, they might send out a notice to prevent people from using rivets from the same batch.

 

[szicree]

Rivets have a date on em? I've bought rivets from spruce plenty of times, and they just stick em in a little bag. I've never noticed any dating.

 

[Bob Axsom]

The date tells essentially nothing

All you can say about a dated bag of rivets is they were all made before the date on the bag (assuming the date is not in error, a computer printed "1936" for example). There is absolutely nothing to preclude suppliers that are not the manufacturers from mixing many maufacturers parts from many production runs and non standard parts. They are treated as bulk stock by suppliers and they buy where they can get the best deal.

This kind of thing is a problem for aircraft manufacturers. In the early days of the F-15 we were having control knobs in the ICNIC (Intrgrated Communication/Navigation/Identification Control) panels breaking in the field. The specs were good and there was no good reason for the failures. A chemical analysis revealed that the supplier was substituting a cheap look-a-like material that did not have the physical properties of the specified material that were necessary for the application. We turned it over to the authorities for processing but RV builders are on their own.

Material and process control are very expensive they are applied with a certain amount of record keeping and trust in the aircraft world and they are carried to the extreme in the space flight hardware applications. In the RV world I am impressed with the quality and consistency of hardware we receive with no controls at all.

There are exceptions like the fact the if you order O-rings for the puck on Cleveland brakes from Aircraft Spruce they will substitute a different part with the same dash number that has different physical dimensions and will leak. I have talked to Aircraft Spruce about this and tech support engineers at Cleveland. They are both strong in their opposing positions Aircraft Spruce is convinced that it is a good substitute and Cleveland says it is absolutely not authorized and has never been tested. I have tested it in the field and the substitute parts leak! Meanwhile, Van's sells the correct O-ring.

"Let the buyer beware" is what we live by but we have no systematic control over what we are supplied. As I said at the beginning the date on the bag is no more than a date on a bag. The next later dated bag may have much older rivets in it.

Bob Axsom

 

[az_gila]

Traceability

Rivets have a date on em? I've bought rivets from spruce plenty of times, and they just stick em in a little bag. I've never noticed any dating.

Mil-spec items always have a date code on them (and probably a production lot number). The date code is usally in the format xxyy were xx is the year, and yy the week. This is for traceability.

I bet Spruce's "big bag" has a date on it, but does not have a storage limitation on it....

I would hope Vans didn't get a "special deal" on a lot of rivets that failed acceptance test....

gil in Tucson

 

[Bob Axsom]

Well not completely

The individual MIL-specs state whether the common 4 digit date code is required and I assure you none of our suppliers maintain traceability to the manufactures lots. During the Reinventing Government years wholesale cancelling of MIL-Specs occurred and the wealth of standards that had been developed over many years were effectively flushed. The old specs can still be used for procurements but the specification is by the P.O. or procurement Spec. and the enforcement is by the applicable legal system and not the U.S. Military/Government. Things are so slimey that failed lots of ICs can be screened and those that pass can be included in a new lot, given a lot date code associated with the later combined lot and delivered as if it they were all products of a homogeneous run worthy of sample acceptance testing. One of these cases was so bad I turned it over to the NASA Inspector General organization. They looked into it but I do not know if any action was taken.

BobAxsom

 

[az_gila]

Depends which supplier...

The individual MIL-specs state whether the common 4 digit date code is required and I assure you none of our suppliers maintain traceability to the manufactures lots. During the Reinventing Government years wholesale cancelling of MIL-Specs occurred and the wealth of standards that had been developed over many years were effectively flushed. The old specs can still be used for procurements but the specification is by the P.O. or procurement Spec. and the enforcement is by the applicable legal system and not the U.S. Military/Government. Things are so slimey that failed lots of ICs can be screened and those that pass can be included in a new lot, given a lot date code associated with the later combined lot and delivered as if it they were all products of a homogeneous run worthy of sample acceptance testing. One of these cases was so bad I turned it over to the NASA Inspector General organization. They looked into it but I do not know if any action was taken.

BobAxsom

Bob... I'm sure that's true for ICs.... especially since few are even made in the US any more....

I'm not sure if that's the case for our missile fasteners... I'll ask a Supply Chain person tomorrow....

Update

If you buy from this supplier, they say they give full traceability.

http://www.gen-aircraft-hardware.com/certifications.asp

I think there is also a Federal law trying to combat bogus fasteners, but I can't remember details...

gil in Tucson

 

[cytoxin]

temperature

what was the temp? i have wittnessed some an470-4-7s (5-6rivets.)shear in a diagonal way when it was cold (30-35)and i was using the squeezer..came back the next day in the warmth and no such problem.

 

[AX-O]

what was the temp? i have wittnessed some an470-4-7s (5-6rivets.)shear in a diagonal way when it was cold (30-35)and i was using the squeezer..came back the next day in the warmth and no such problem.

temp in the garage was around 85 deg F.

 

[cytoxin]

not to beat a dead horse, buuutttt

do you have any pics. mine seem to have been real obvious. then some times the surface seems to act as if it were annodized. i have some military surplus rivets left over that were probally 20 years old when i got them in 89. shot them last year went fine. i think it is safe to assume you hyave a batch issue....

NOTE mine are always different colors as in your pic.

 

[az_gila]

Anodized...

do you have any pics. mine seem to have been real obvious. then some times the surface seems to act as if it were annodized. i have some military surplus rivets left over that were probally 20 years old when i got them in 89. shot them last year went fine. i think it is safe to assume you hyave a batch issue....

NOTE mine are always different colors as in your pic.

WW (huh?)

It is possible that your rivets are anodized. If they came from an unknown source (surplus?), a letter A, D, or N in the part number after the length indicates an anodized finish.

Our "standard" rivets (no letter after length) are alodined (a.k.a. chemical surface treatment), not anodized.

Could your rivets be surplus with the full part number unknown?

The anodize is per MIL-A-8625, Type II, Class 1 (A or D) or 2 (N) if you want to look it up....

gil in Tucson

 

[Marc DeGirolamo]

Bad rivets ?

When I was building the spar on my -4 (I know the dinosaurs roamed the earth back then ) I noticed, after I was all done, that there were rivets (the 1" long ones) that looked like they had hairline cracks in them......I nearly had a stroke but after that passed I took a magnifying glass and had a better look.....I decided NOT to take a chance and drilled out all of the affected ones (about 16 in all ). I had some really long ones left over so I cut those to length and installed these.....and after squeezing they looked fine. For what its worth, I squeezed them all with a hydraulic ram so there was no hammering at all.

I was working at a research facility at the time and had access to a scanning electron microscope. I thought it would be cool and useful to have a look at the crack through it....I brought them in to work one day and had the technician scan them for me.......here is what they looked like.

These are both of the same crack...one is magnified more (x10).
Turns out that the cracks I was seeing were there but it was the anodized surface which had cracked/flaked. I am not a metalurgist and won't speculate whether this would have led something more serious but I felt better anyway having changed those puppies.....Could possibly have been an old batch or rivets mixed in with a more recent batch I don't know...
..thought this may be of interest ......

 

[Bob Axsom]

Power Squeezer Related?

It is at least interesting that both builders experiencing this condition were using power squeezers. It is easy to imagine the user applying the squeeze with the rivet not fully set in some cases due to the operator's relaxed handling, some surface embrittlement related to the manufacturing finish batch processing and no "hammer" in the assembly process to blend it in.

Bob Axsom

 

[cytoxin]

no

WW (huh?)

It is possible that your rivets are anodized. If they came from an unknown source (surplus?), a letter A, D, or N in the part number after the length indicates an anodized finish.

Our "standard" rivets (no letter after length) are alodined (a.k.a. chemical surface treatment), not anodized.

Could your rivets be surplus with the full part number unknown?

The anodize is per MIL-A-8625, Type II, Class 1 (A or D) or 2 (N) if you want to look it up....

gil in Tucson

no they are not annodized. the surplus ones are just plain silver the others are vans or spruce (hmm?) i only squeezed some of the surplus ones because this issue came up a few months back.

 

[Marc DeGirolamo]

hairline fractures

[and no "hammer" in the assembly process to blend it in.]

I would tend to think that squeezing is a better way of setting any rivets if possible, even if you stop and start to get a finished shop head.......stop and start with a rivet gun or hammer too many times and see what happens.......a hundred or more were set (squeezed) in exactly the same way and only 16 had these little stress cracks, and they were all the same length .....temperature in the shop was warm so take that out of the equation. I believe that there was a difference in those rivets (in the anodizing) but we'll never know because I'm not taking them out of the spar to do a comparative test....