J

JKevin

Well Known Member
So...

I am starting construction of my recently-purchased RV-6 kit. Jig built, ready to go.

The kit is from the 90's and all of the hardware, including rivets, is what came with the kit when new.

I have read about "fresh" vs "old" rivets and the potential for problems using old rivets.

Science or old wives' tale?

I would hate to throw away what appear to be perfectly good rivets, but it's not like it would break the bank to buy new...

Any input would be appreciated.
 
They are fine...shoot 'em!

Your rivets are fine...use them. There is no shelf life on AD rivets as used on the RV kits. There are rivets known as "ice box" rivets, a completeley different alloy than AD rivets,which are simply rivets pre-anealed for easier installation which will self age harden after a short period of time. Those rivets need delivered in a frozen state or locally annealed on site, then installed before they become re-hardened. I make my living in the "big jet" overhaul industry and use every imaginable rivet alloy there is..we don't throw any away because they are "old"
 
fixnflyguy said:
Your rivets are fine...use them. There is no shelf life on AD rivets as used on the RV kits. There are rivets known as "ice box" rivets, a completeley different alloy than AD rivets,which are simply rivets pre-anealed for easier installation which will self age harden after a short period of time. Those rivets need delivered in a frozen state or locally annealed on site, then installed before they become re-hardened. I make my living in the "big jet" overhaul industry and use every imaginable rivet alloy there is..we don't throw any away because they are "old"
Click to expand...

Bill is correct.

I have used most of the new rivets that came with my RV-8 tail kit but also added a few rivets left over from my RV-6 kit. My RV-6 has been flying over 19-years and over 3,200 hours. Could not tell the difference between the 20+ year old rivets and the newer rivets.
 
The 2117 alloy rivets will experience age hardening. They can be annealed, which is technical and requires accurate control of heat source and following procedure closely.

One benefit is reducing gun pressure from 80 to about 40 psi and the # of hits to form the shop head from (many) to four simple "plops" (by the sound of the rivet gun striking off).

The chief benefit is better installation with less sheet distortion from swelling of the shank, less chance of the gun "walking" - especially if you're riveting solo and less collateral damage if you're attempting to rivet close to structure.

It's worth mentioning that good dimpling practices are a generally unrealized benefit to the process as a whole and airframe useful life.

mjb
 
Marc Bourget said:
The 2117 alloy rivets will experience age hardening. They can be annealed, which is technical and requires accurate control of heat source and following procedure closely.

One benefit is reducing gun pressure from 80 to about 40 psi and the # of hits to form the shop head from (many) to four simple "plops" (by the sound of the rivet gun striking off).

The chief benefit is better installation with less sheet distortion from swelling of the shank, less chance of the gun "walking" - especially if you're riveting solo and less collateral damage if you're attempting to rivet close to structure.

It's worth mentioning that good dimpling practices are a generally unrealized benefit to the process as a whole and airframe useful life.

mjb
Click to expand...

I think that is incorrect.

The 2117 alloy can age-harden, however our rivets (the ones with a single dimple in the manufactured head) are shipped in a -T4 condition.

From an aluminum properties spec. sheet.

Machinability of AL 2117 is good in the T4 condition (heat treated and aged). Machining is more difficult in the annealed state and use of oil lubricant is advised for all operations.

They are already age hardened.
 
I respectively disagree.

Despite what you have read above, I can tell you from first hand experience that the AN470AD4 rivets will most definitely age harden, and Van's even points this out in the manual on the page showing unacceptable rivets. My empennage had a 10 year break from when I purchased it to when I picked up on things again. I found that the AN426AD3 rivets didn't harden, but the AN470AD4 rivets were really hard to squeeze. In addition I found that many of the shop heads were developing 45 degree shear type hairline cracks. I this drilled out a bunch of rivets and replaced them with new rivets, which set much more easily. If I was in your situation, I would purchase some new AN470 rivets and just compare the difference in force required to set them. If your old rivets are noticeably harder to set, don't risk it and get new rivets. Rivets are dirt cheap in the scheme of things, especially compared to the time wasted and risk of structural damage associated with drilling out hairline cracked rivets in the future.
Tom.
 
Interesting, my experience has been that I can't tell the difference between new rivets packed in recent kits that I have mixed up with 20+ year old rivets in the same container... They all seem to set the same.

I've never segregated received rivets...:)
 
Gil,

Building a T-18 in the 70's, in the midst of the Aerospace industry, I'd pick up "fresh" rivets from Fullerton Airparts (delivered every Thursday Aircraft Spruce was just selling wood back then). Fresh, they'd drive at 50# the first day and I'd have to bump the pressure, and the number of hits, day by day till about 80 psi. I coffee cans full of rivets from back then that will shear as mentioned above. I'll use some as a demo at the Aircraft Sheetmetal Workshop I'll be giving at the Capitol Airshow, next year.

Just bought myself a trick digital HT oven and am going to experiment with "W" temper as well - once I get myself a suitable hardness tester.

mjb
 
An older thread on Old Rivets

Old rivets have been talked about before.

Bottom line is the Mil Spec says: "Alloy 2117 rivets retain their characteristics indefinitely after heat treatment and can be driven anytime. Rivets made of this alloy are the most widely used in aircraft construction."

Summary with the facts are here.

IF our rivets get old, show me the proof in a document that they have an age limit. Show me the Mil Spec that says they need a shelf life. If they did have a time limit, why is there no use by date on the packaging?
 
Gary,

I took the time to review the posts and links in the prior thread. Mostly a repeat of what is above.

Gil Alexander, on 11-26-07, made the closest to a comprehensive post - representative of the prior thread.

?Alloy 2117 rivets have moderately high strength and are suitable for riveting aluminum alloy sheets. These rivets receive only one heat treatment, which is performed by the manufacturer, and are anodized after being heat treated. They require no further heat treatment before they are used. Alloy 2117 rivets retain their characteristics indefinitely after heat treatment and can be driven anytime. Rivets made of this alloy are the most widely used in aircraft construction.

I would contend that "diddling" with the heat treat of our rivets in an uncontrolled fashion could be dangerous unless each batch processed is checked for mechanical properties...?

Also worth noting is Gil?s further observation:

?It's sometimes easier to ignore the experts and read the actual Mil Spec....? (End quotes)

Comment:

I have been certified by the FAA to give continuing ed courses in aircraft sheet metal for IA?s. I say this only to establish that my efforts in this area have passed some scrutiny (nothing more!). I do not say this expecting others to accept, lock, stock and barrel, what I say. What is intended is that I present enough perspective to prompt others to investigate further what is set out below.

Processing protocols are mentioned in the thread only in passing. The definitive instructions for dealing with 2117 can be found in the Alcoa Product Guide and the ASM-4 (I have both). One thing not mentioned is you should only heat treat, or temper rivets that are clear anodized. Alodyne and colored anodizing contaminates the 2117 in the heat treating process compromising its properties.

While the material characteristics are alleged as being retained indefinitely, what is missing is ?the rest of the story?.

ON INSTALLATION, an aged, (harder) rivet will subject the sheet into which it is being installed to greater distortion, if the rivet doesn?t first exhibit disqualifying properties or configuration. This includes forming a ?tulip? head, rather than a ?donut?, diagonal shear fracture lines and various other negative characteristics set out in MIL-R-47196A; MIL-STD-403C; MIL-STD-40007[1]; NACA TN-805 and NACA TN-948.

I submit that the general statement that they ?retain their characteristics indefinitely? is acceptably accurate because the safeguards set out in the above-referenced technical works, if followed, effectively weed out the rivets that lose these ?characteristics.?

Back in the early 70's, I had access to (then) state-of-the-art Heat Treat Ovens (analog controls). The problem with which was inadequate temperature controls. Sometimes the temp ?drift? went outside the processing temperature ?window? and the responsible technician scrapped the product. Now days, digital temp controllers can keep temperature spread within a few degrees.

So, I agree that ?diddling? is substandard. But the responsible, knowledgeable and diligent technician can achieve superior results.

mjb
 
For those that do not believe mjb, check out FAA-8083-30_Ch05.pdf page 5-26 lower left hand column.

It says exactly what Gil said a few years back.



Alloy 2117 rivets have moderately high strength and
are suitable for riveting aluminum alloy sheets. These
rivets receive only one heat treatment, which is performed
by the manufacturer, and are anodized after
being heat treated. They require no further heat treatment
before they are used. Alloy 2117 rivets retain their
characteristics indefinitely after heat treatment and can
be driven anytime.


Still waiting for someone to post a link to a document that says something different.
 
Hi Gary. See below for a section from the RV-7 manual that talks about old rivets and the need to replace them. You can also go to places like Matweb that talk about age hardening of alloys. For both T1 through T4 alloys, you will see that they are "naturally aged to a substantially stable condition". They key word here being "substantially", which means that further aging may occur. I'm heading back to the shop shortly and will see if I can find some of these old rivets and would be happy to post you a sample of both so that you can squeeze them for yourself and experience the difference first hand. When I received the new rivets I cleaned out most of the old rivets for fear of cross contamination, but I'll have a look and see if I have any left.
Keep in mind I'm not doing this to prove you wrong, but just to make sure the individual who initiated this post doesn't make the same mistake I did and have to drill out a bunch of rivets. I wish that someone had brought it to my attention earlier.
Tom.

http://www.matweb.com/reference/aluminumtemper.aspx


1nxrw9.jpg
 
tgmillso said:
Hi Gary. See below for a section from the RV-7 manual that talks about old rivets and the need to replace them. You can also go to places like Matweb that talk about age hardening of alloys. For both T1 through T4 alloys, you will see that they are "naturally aged to a substantially stable condition". They key word here being "substantially", which means that further aging may occur. I'm heading back to the shop shortly and will see if I can find some of these old rivets and would be happy to post you a sample of both so that you can squeeze them for yourself and experience the difference first hand. When I received the new rivets I cleaned out most of the old rivets for fear of cross contamination, but I'll have a look and see if I have any left.
Keep in mind I'm not doing this to prove you wrong, but just to make sure the individual who initiated this post doesn't make the same mistake I did and have to drill out a bunch of rivets. I wish that someone had brought it to my attention earlier.
Tom.

http://www.matweb.com/reference/aluminumtemper.aspx


1nxrw9.jpg
Click to expand...

Are we mixing up heads?

Your earlier post talks about cracking on the shop heads, but the picture from Vans specifically mentions manufactured heads.

I've screwed up many rivets, both old and new :), but never cracked a manufactured head.
 
Hi Gil. Fully aware that Tony's pictures above depict a cracked factory head, but these are occurring on the shop head. This post finally got me motivated enough to break out the borescope I purchased to inspect the remainder of the rivets I was concerned about in my empennage. Sure enough, I found one more cracked rivet. It is an AN470AD4-6 rivet that was fabricated in 2004 and installed in 2015. It is located on the bottom of the empennage and was squeezed in place, so there was no chance that it was work hardened with a rivet gun. This was the same with the ones that I set on the horizontal stabilizer. They were squeezed and not driven/bucked, but I still had 3 cracked rivets (shop head). Van's are aware of the issue, as I spoke with the support line on 9 Dec 2015 (Gus) about this. They know it happens and recommended to just drill out and replace the cracked rivets that were accessible. This occurred, and now that I have found one additional rivet with the borescope, I will drill it out and either replace with an LP4-3 or an AN470 of my new batch. I checked the last of my un-used empennage rivets, and I had replaced them all with fresh rivets, so I unfortunately don't have any that I can send you for testing. Maybe someone else with a 10+ year old kit that has encountered the same thing can send you a sample. Last year when I identified the problem, I spoke to an aircraft technician about it and he commented to me that their supplier provided rivet batches with a published expiry date.
The most important thing is Kevin is aware of the issue, which he undoubtedly now is.
Tom.

dfj8sn.jpg
 
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