What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Rivet age

hardegg

Member
I've heard the term age hardened applied to rivets. Can anyone advise if this is true and at what age do rivets start becoming to hard and brittle to be safely used?
 
I've used some very old rivets before. Head markings indicated they were correct grade and type, but the shop heads kept cracking. May 10%, but still a very frustrating amount of rivets needed to be drilled out. Eventually I threw them out and started using newer rivets without any problem. Maybe a bad batch from 20 years ago?
 
It is real

Age hardening is a real property/phenomenon for some materials. It is not a simple or easy topic to convey if someone doesn’t already have a basic understanding of mechanics of materials (books/Theseus are written about it, specialist employed solely for their related expertise, etc.). You’ll often hear of some heat treatments as “artificially aged”. It can take days (google Ice Box rivets) or decades. It’s not uncommon to find some extra hard rivets from old mil surplus bags at air shows. That said, I can’t quantify the OP’s question. Too many unknowns.
 
I've used some very old rivets before. Head markings indicated they were correct grade and type, but the shop heads kept cracking. May 10%, but still a very frustrating amount of rivets needed to be drilled out. Eventually I threw them out and started using newer rivets without any problem. Maybe a bad batch from 20 years ago?

I had the same issue with some AN470AD4-5s. They would do ok (0-2 cracks within limits) when bucked but would fail about 90% when squeezed. Thread is here.

Replaced with rivets from Van's and haven't had any issues since.
 
Old Rivets

30 to 40 year old AN426 & 470 rivets seem to be just fine. Always alert for quality issues no matter the age.

Don Broussard
RV9 Rebuild in Progress
57 Pacer
 
I was restarting an old kit and asked Vans. Response was pretty much 'build on'. Haven't thought about it again until this thread. Any bad rivets have been from not securing the work properly or just wanting to get that last rivet in when I knew I was too rushed or tired (in other words, my fault).
 
If properly heat treated, the rivets used on Van's kits age harden in less than two days. After that, it doesn't matter how old they are.

So, don't worry about it.

They can be re-solution heat treated to re-start the process, but that is another thread.
 
Years ago when I started building my -6A, 1998, I used the Matronics Rv-List and I seem to recall there being a posting by somebody using a dental kiln to anneal rivets to make them easier to squeeze or buck. You might try a search on the Rv-List. Marty
 
Years ago when I started building my -6A, 1998, I used the Matronics Rv-List and I seem to recall there being a posting by somebody using a dental kiln to anneal rivets to make them easier to squeeze or buck. You might try a search on the Rv-List. Marty

Most likely ice box rivets that are 2024 AL not the AD rivets used in the RV. Usually used for large rivets.
 
Last edited:
Years ago when I started building my -6A, 1998, I used the Matronics Rv-List and I seem to recall there being a posting by somebody using a dental kiln to anneal rivets to make them easier to squeeze or buck. You might try a search on the Rv-List. Marty

That was Dave Anders. And he used the AD rivets supplied with the kit.
 
Rivet Age

Years ago when I was building a -4 I spent some time on this topic. Mostly because I wasn't very good at driving rivets and was looking for a easier way. I just dug out my notes from back then.

I reached out to several people over the course of 2-3 months. The two who pointed me in the right direction were are materials professor at Iowa State University and an engineer from Alcoa. They both told me the same thing.

Rivets are made from 2117 alloy which does age harden. It is possible to "soften" them by re-heating them. To do this correctly, you must heat them to their critical temperature which is 935 degrees. I used a dental oven a buddy of mine let me borrow (I still have it). The recipe is to heat for 15 minutes and then quench in water within five seconds. Quality control consists of hitting them on an anvil with a hammer. If they crack, you did it wrong. Don't drop them when you take them out of the oven!

I did it on my -4 and it was definitely noticeable in terms of ease of driving the rivet. I'm not doing it now, but it was a fun project. Like everything in this hobby, a great way to learn new stuff.

If you know a dentist, ask to borrow his oven and try it.
 
Last edited:
Years ago when I was building a -4 I spent some time on this topic. Mostly because I wasn't very good at driving rivets and was looking for a easier way. I just dug out my notes from back then.

I reached out to several people over the course of 2-3 months. The two who pointed me in the right direction were are materials professor at Iowa State University and an engineer from Alcoa. They both told me the same thing.

Rivets are made from 2117 alloy which does age harden. It is possible to "soften" them by re-heating them. To do this correctly, you must heat them to their critical temperature which is 935 degrees. I used a dental oven a buddy of mine let me borrow (I still have it). The recipe is to heat for 15 minutes and then quench in water within five seconds. Quality control consists of hitting them on an anvil with a hammer. If they crack, you did it wrong. Don't drop them when you take them out of the oven!

I did it on my -4 and it was definitely noticeable in terms of ease of driving the rivet. I'm not doing it now, but it was a fun project. Like everything in this hobby, a great way to learn new stuff.

If you know a dentist, ask to borrow his oven and try it.

Or, alternatively, just buy new rivets. Rivets are cheap. Too much time and effort for me, but as you say, a good education!
 
Buying new rivets worked well in the early 70's in SoCal with all the Aerospace activity. Thursday morning at Fullerton Air Parts (Aircraft Spruce at that time was "down the street, dealt only with wood and was by appointment only) got you rivets that would drive at 60 psi or so, raising to 80 psi by Saturday.

I had access to "professional" HT ovens, analog controlled, and following the above procedure, gave you rivets that drove at 40 psi, barely "tickling" the rivet gun trigger, "plop, plop, plop, plop" If you kept them on dry ice, the pressure requirements increased more slowly, but eventually got to 80 psi or more after a few days. Soft rivets drive with minimal, if any, distortion of the surrounding sheet metal as the clinch pressure was less or equal to the "stretch" resistance of the skins you were riveting.

935 deg F, yes, but you need a digital controller now. The old analog controllers were +/- 10 deg and you risked exceeding 938 deg, which scrapped the rivets.

Also, only anneal clear anodized rivets. Annealing colored rivets is a chemical no-no.

Onward and upward
 
Last edited:
It was a fun experiment to solution heat treat some rivets back in the 90's. I did some and tested them on a material tester. The sheared right at book value. Older age hardened samples sheared higher than book.
Freshly treated rivets can be squeezed with a pair of pliers, and universal heads can easily deform or slide off to the side. Flush rivets would lose the dimple. Fun stuff, but I would only do that for special situations like riveting the hinges to fiberglass, or a tricky trailing edge rivet. Unfortunately, I burned out my oven elements annealing some stainless steel this year, so I'm probably out of luck for future treatments.
 
Back
Top