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Thinnest material for AD5 rivet

JMyers1

Member
I am new to solid rivets. I am riveting a .040 part to a .025 part that are pre-drilled #20. I used some scrap and countersunk and back riveted them and the thinner .025 part seems to be buckling. I know my technique is not perfect but I've made a few attempts and none look great.

Is .025 just too small for this size rivet or am I doing something wrong here? I do have dimple dies, maybe I should have dimpled the thinner material (or both)?
 

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When installing flush rivets in thin sheet, you always dimple counter sink, all the layers that are common to the rivet.
So basically, the dimple for the rivet head should be nesting in the dimple of the other sheet it’s being attached to.
It is also best practice to form the shop head on the thicker material if they’re not the same thickness, and if there’s no other reason to prevent you from doing so.
 
When installing flush rivets in thin sheet, you always dimple counter sink, all the layers that are common to the rivet.
So basically, the dimple for the rivet head should be nesting in the dimple of the other sheet it’s being attached to.
It is also best practice to form the shop head on the thicker material if they’re not the same thickness, and if there’s no other reason to prevent you from doing so.

Thanks, I tried dimpling and the results were much better. In this case the thicker material is on the outside of the airplane. For my test material I have a back riveting plate, but I will need a back riveting bucking bar for the actual part. I have a 2.5lb bucking bar, is that sufficient for back riveting? I notice back riveting bars are sold as such and tend to look different.
 
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I am new to solid rivets. I am riveting a .040 part to a .025 part that are pre-drilled #20. I used some scrap and countersunk and back riveted them and the thinner .025 part seems to be buckling. I know my technique is not perfect but I've made a few attempts and none look great.

Is .025 just too small for this size rivet or am I doing something wrong here? I do have dimple dies, maybe I should have dimpled the thinner material (or both)?
AD5 is a big diameter rivet to use in 0.025" sheet. That combination is outside the range for which MIL-HDBK-5J provides strength data, which means it is unlikely to develop the full strength of the rivet cross-section. Unless you're using it just as a hole filler, I'd check with the designer/supplier that it's really intended to be used here.
 
AD5 is a big diameter rivet to use in 0.025" sheet. That combination is outside the range for which MIL-HDBK-5J provides strength data, which means it is unlikely to develop the full strength of the rivet cross-section. Unless you're using it just as a hole filler, I'd check with the designer/supplier that it's really intended to be used here.
I think the reason it is not on the chart is because the tear-out strength of .025 material is way below the shear strength of an AN5 rivet, so there is no benefit using a fastener that large. Adding to that the difficulty of installing without causing distortion in the light material.

2.5 pounds might be a bit light for free hand back riveting a 5/32 rivet.
Do you need to back rivet because you have only a 2X gun?
 
One thing that might help is putting a short piece of fuel hose over the end of the rivet. When you squeeze or drive the rivet, the shop head is formed inside the hose, which pulls off easily. What the hose does is force the work pieces together.

Dave
 
An easy rule of thumb: If countersinking results in a hole larger than the shank of the rivet, then you should be dimpling, not countersinking.
 
. For my test material I have a back riveting plate, but I will need a back riveting bucking bar for the actual part. I have a 2.5lb bucking bar, is that sufficient for back riveting? I notice back riveting bars are sold as such and tend to look different.
Just to be sure you understand the terminology: In ‘normal’ riveting, the gun goes on the factory head, and a bucking bar goes on the rivet tail. The bucking bar will ‘bounce’ slightly. In ‘backriveting’, the gun goes on the rivet tail and a ‘back riveting plate’ is used to back the rivet head. Many builders mount the back riveting plate on their work bench or concrete floor, so they have a huge effective mass. If you really meant backriveting, no, a 2.5 lb bar is not heavy enough. Here’s why: the rivet swells in the radial direction as well as forming a tail. As you hit the tail, the 2,5 bar will allow the head to lift up a bit. But then, on some hit, the radial swelling of the rivet will have it pushing sideways against the hole, with enough friction that the 2.5 lb bar cannot push it back down flush. You’ll end up with the rivet head sticking up, off the work.
 
AD5 is a big diameter rivet to use in 0.025" sheet. That combination is outside the range for which MIL-HDBK-5J provides strength data, which means it is unlikely to develop the full strength of the rivet cross-section. Unless you're using it just as a hole filler, I'd check with the designer/supplier that it's really intended to be used here.

It's actually intended for a pull rivet, which is the reason for the larger size. An AD5 solid rivet is overkill, I am doing it primarily to gain experience with solid rivets and also because it looks cleaner.
 
I think the reason it is not on the chart is because the tear-out strength of .025 material is way below the shear strength of an AN5 rivet, so there is no benefit using a fastener that large. Adding to that the difficulty of installing without causing distortion in the light material.

2.5 pounds might be a bit light for free hand back riveting a 5/32 rivet.
Do you need to back rivet because you have only a 2X gun?

I ordered a refurbished 3X gun from the yard store and they sent me a 2X gun. I am waiting to hear if they will exchange it (I ordered it in November and just recently noticed after coming back to my build after some winter blues idle time). I was thinking I needed to back rivet but I actually don't, not sure why I was stuck on that. But if I am stuck with a 2X gun it sounds like I actually do need to back rivet? If so I might spring for another gun.

In Paul Dye's excellent video he suggest .032 is the largest size to dimple. Since the thicker sheet here is .040 should I be countersinking the thicker and dimpling the thinner? I watched a few videos and .040 seems to be borderline for either. Also, every guideline/video shows the thinner material on the manufactured end which I don't think I can do since that would put the shop end on the outside of the airplane and wouldn't look any better than a pull rivet head.

To avoid dimpling I tried using the universal head and I ended up with the thin end bending a bit. Maybe I should just go with pull rivets and save solid rivets for another part that isn't final hole drilled.
 

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I ordered a refurbished 3X gun from the yard store and they sent me a 2X gun. I am waiting to hear if they will exchange it (I ordered it in November and just recently noticed after coming back to my build after some winter blues idle time). I was thinking I needed to back rivet but I actually don't, not sure why I was stuck on that. But if I am stuck with a 2X gun it sounds like I actually do need to back rivet? If so I might spring for another gun.

In Paul Dye's excellent video he suggest .032 is the largest size to dimple. Since the thicker sheet here is .040 should I be countersinking the thicker and dimpling the thinner? I watched a few videos and .040 seems to be borderline for either. Also, every guideline/video shows the thinner material on the manufactured end which I don't think I can do since that would put the shop end on the outside of the airplane and wouldn't look any better than a pull rivet head.

To avoid dimpling I tried using the universal head and I ended up with the thin end bending a bit. Maybe I should just go with pull rivets and save solid rivets for another part that isn't final hole drilled.
You could try a doubler on the inside of the thin sheet, e.g. make a washer from .040 to go under the shop head.

If the holes have been pre-drilled for pulled rivets then that may well be the best solution. I don't know what is the application for the rivets but some airframes e.g. Zenith are specifically designed to use special 5/32 pulled rivets and these form part of the overall engineering "solution".
 
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I ordered a refurbished 3X gun from the yard store and they sent me a 2X gun. I am waiting to hear if they will exchange it (I ordered it in November and just recently noticed after coming back to my build after some winter blues idle time). I was thinking I needed to back rivet but I actually don't, not sure why I was stuck on that. But if I am stuck with a 2X gun it sounds like I actually do need to back rivet? If so I might spring for another gun.

In Paul Dye's excellent video he suggest .032 is the largest size to dimple. Since the thicker sheet here is .040 should I be countersinking the thicker and dimpling the thinner? I watched a few videos and .040 seems to be borderline for either. Also, every guideline/video shows the thinner material on the manufactured end which I don't think I can do since that would put the shop end on the outside of the airplane and wouldn't look any better than a pull rivet head.

To avoid dimpling I tried using the universal head and I ended up with the thin end bending a bit. Maybe I should just go with pull rivets and save solid rivets for another part that isn't final hole drilled.
As you can see in your middle photo, if you dimple the top sheet, you must make room for that dimple to go into the bottom sheet - either by dimpling the bottom sheet too, or, if it is thick enough, countersinking it.
If you bent over the tail, that means you didn't hold the bucking bar square to the tail, or maybe, the tail is too long. A rule of thumb is that the exposed length of the rivet tail, before riveting, should be about 1.5 times D, where D is the rivet diameter.
 
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