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Rivet Head Thickness Max?

AlinNS

Well Known Member
I'm trying to figure out why there is a maximum rivet head thickness in the Mil Spec. Rivet diameter has only a minimum - this seems to make sense. Wouldn't it also make sense to have only a minimum head thickness? I'm referring to the shop head dimensions.

Thanks.
 
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Published Spec.

Al:
What you're looking for is right here (https://www.vansaircraft.com/public/Specs.htm#TABLE III)

If you use the proper length rivet (in terms of height in "diameters), you'll need only to verify the diameter of the shop head. After setting a few thousand, you really won't need a gage to verify your work - your eyes will be calibrated by that time.
Terry, CFI
RV9A N323TP
 
Hi Terry, thanks.

I have been using the numbers from that table and am wondering "why" there is a max head thickness published.

I have been pounding a lot of them lately and your right - it's suprising how accurate you can be just by looking.
 
The "why" is because of the increased potential for cracking in the formed tail. If it is to large, an excessive amount of material is being deformed and the tails may crack. That is covered in some of the Mil documents on riveting. It is surpirsing that the FAA doesn't address this in AC43-13-1B, but they don't
 
This is what I keep taped above my work bench.

IMAGE_64.jpeg



IMAGE_65.jpeg



By the way Al I have hiked all through Cape Breton Highlands National Park, whale watched off Meat Cove, visited Peggys Cove and toured the Alexander Graham Bell Museum.
Cape Breton is one of the most spectacularly beautiful places I have ever visited.
 
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That makes sense Dan, thank you.

Arnie, I have never seen that chart before. Interesting, the one I use shows no max diameter. I couldn't agree with you more about Cape Breton. It holds a special place in my heart. If I ever truly retire I plan to buy land there, put in a grass strip and welcome everybody so they can see a wonderful part of Nova Scotia for themselves. If you are interested there is a very nice paved runway called Margaree that is not too far from the Highlands - not a very we'll advertised strip and very under used.
 
I'm also a bit confused! When The instruction say: "the 5 rivet is the correct length" or "the rivet callout is correct on the plans" but the checked length give a to short rivet length so a really short upset head height when a correct diameter is realized, should this short head height considered as OK? ( HS-609PP on HD-603PP and HS-411PP on VA-146)?? Anyone can help?
 
I'm also a bit confused! When The instruction say: "the 5 rivet is the correct length" or "the rivet callout is correct on the plans" but the checked length give a to short rivet length so a really short upset head height when a correct diameter is realized, should this short head height considered as OK? ( HS-609PP on HD-603PP and HS-411PP on VA-146)?? Anyone can help?

If it meets specs, it is ok. There is a wide tolerance. See the link in the post from Terry above.
There are a few places in the plans that call out incorrect rivet lengths on most of the models. Check before setting them to see if the protrusion is within tolerance first. If needed, up size or down size. After a bit, you will gain a feel for what is right just by eyes and touch.
 
I'm also a bit confused! When The instruction say: "the 5 rivet is the correct length" or "the rivet callout is correct on the plans" but the checked length give a to short rivet length so a really short upset head height when a correct diameter is realized, should this short head height considered as OK? ( HS-609PP on HD-603PP and HS-411PP on VA-146)?? Anyone can help?

Well I think for the first time I can answer a question instead of asking one!

The formula that many use to determine the length of a rivet (1.5 x the diameter of a rivet, etc) is a guide to get you in the ballpark. A shorter length rivet may indeed still produce an acceptable shop head. For example: a 3/32 rivet requires a MINIMUM shop head diameter of .122" while the shop head height MAY VARY between .038" - .050".

The best thing I did was put away my little gauge and pick up my dial calipers to discover just how big/small a shop head can be and still be acceptable. I was surprised at the difference between min and max shop head height. Now I can confidently use that little purchased gauge and know what it means.

Vans uses Table III from the Mil Spec (its on their website). I'd bet when you pound a rivet that they call for (that is shorter than what the formula comes up with) you will still come within specs for min height. If not, that would warrant an email or a call to them just to find out why.

I don't have the luxury of a Tech Councillor or the time to attend an EAA Seminar but I have sure pounded a lot of practice rivets and admittedly am learning the hard way!

If I'm leading Naigool astray please somebody speak up... :)
 
Al, you do have a local to you tec. councillor , Ian Patrick. Unless he has given up recently which I doubt. He was here a few months ago looking at my project. Let me know if you would like his contact info?
 
How 'bout that, he just lives up the road from me. I knew he had an aircraft but I didn't know he did that sort of thing. I will give him a call. The MDRA guys are proving quite helpful too.

Thank you for the info. Give me a call if you ever get over to the valley!
 
Al:
What you're looking for is right here (https://www.vansaircraft.com/public/Specs.htm#TABLE III)

If you use the proper length rivet (in terms of height in "diameters), you'll need only to verify the diameter of the shop head. After setting a few thousand, you really won't need a gage to verify your work - your eyes will be calibrated by that time.
Terry, CFI
RV9A N323TP

This is completely contrary to everything I have ever been taught and instructed to do by a tech counselor. I was told that diameter has nothing to do with it and proper height is what is critical
 
You can make a rivet gauge easy enough. Quick and simple if you don't trust your eyes.

All the dimensions are in the chart posted above.



The small side is the minimum diameter, the large side is the minimum height.

If the small one fits over the rivet, it hasn't been shot enough.

If the large one passes over the rivet, it has been shot too much (flat).

The hole in the middle is to string a small chain/string through. You'll need to make four, one for each common size rivet.
 
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You can make a rivet gauge easy enough. Quick and simple if you don't trust your eyes.

All the dimensions are in the chart posted above.



The small side is the minimum diameter, the large side is the minimum height.

If the small one fits over the rivet, it hasn't been shot enough.

If the large one passes over the rivet, it has been shot too much (flat).

The hole in the middle is to string a small chain/string through. You'll need to make four, one for each common size rivet.

http://www.aircraftspruce.com/catalog/topages/averyrivetgauge.php?clickkey=119873
 
When I was building the airframe (RV-7), it was very rare to find a callout that was truly too short. What I found most often was that either the 'stack' of material wasn't tight before riveting, or the hole was too big (out of spec). I found that if I drilled #40 (or #30, for 1/8"), deburred with a typical 3 flute deburring tool, and dimpled the hole, it would be significantly larger than the max recommended hole size for that rivet. (And the edges of the hole would scare you if you look at them under magnification, but that's another discussion.) If the hole is oversized, the rivet may end up too short because of the extra volume it takes to fill the hole.

A single flute style deburring tool seemed to help a lot with hole edge quality & seemed to help hole size by not removing too much material during deburring.

FWIW,

Charlie
 
You can make a rivet gauge easy enough. Quick and simple if you don't trust your eyes.

All the dimensions are in the chart posted above.



The small side is the minimum diameter, the large side is the minimum height.

If the small one fits over the rivet, it hasn't been shot enough.

If the large one passes over the rivet, it has been shot too much (flat).

The hole in the middle is to string a small chain/string through. You'll need to make four, one for each common size rivet.


Be careful to get correct results when measuring heights if dimples are involved...

cs_rivet.gif
 
He use to have an RV-6 , I think but I do not think he owns an aircraft presently.
How 'bout that, he just lives up the road from me. I knew he had an aircraft but I didn't know he did that sort of thing. I will give him a call. The MDRA guys are proving quite helpful too.

Thank you for the info. Give me a call if you ever get over to the valley!
 
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