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Below Flush 426-4 Rivets

RV701775

Active Member
When dimpling my rear VS spar, I noticed that the heads of the 426-4 rivets sat slightly below flush in the hole after dimpling. I contacted vans and they replied that this would not allow the rivet to set correctly and the parts should be replaced.

When setting the rivets I used a Cleveland dimple die (CAT 426-4). The rivet sits about .007in below flush. Does anyone else use these dies and are their -4 rivets below flush as well? Is this normal and do the rivets set ok?

https://eaabuilderslog.org/?blprojentry&proj=7gbEJNhMU&e=7p8gFKA3E&listcat=&sid=
 
Substructure dies

Not likely they are #4 Substructure dies. I suggest trying someone elses #4 flush dies.
It's rare, but possible, the dies were not correctly fabricated.
I hope it wasn't a huge expensive part.
 
How thick is the spar material? If it's .040 or .032 then it may be that the dimples were not made with enough pressure. The shoulders in the photo appear a bit rounded and not crisp. That's if the dies themselves are not faulty.

As others have suggested, I'd try another set of dies, even though Cleaveland's have a very good reputation. Yardstore.com are not that expensive and it doesn't hurt to have more than one set of dies.

Also, you could try the dies you have in some thinner scrap material to verify the holes are being dimpled with enough pressure.
 
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How thick is the spar material? If it's .040 or .032 then it may be that the dimples were not made with enough pressure. The shoulders in the photo appear a bit rounded and not crisp. That's if the dies themselves are not faulty.

As others have suggested, I'd try another set of dies, even though Cleaveland's have a very good reputation. Yardstore.com are not that expensive and it doesn't hurt to have more than one set of dies.

Also, you could try the dies you have in some thinner scrap material to verify the holes are being dimpled with enough pressure.

Or even if it isn't .040 or .032 material, it could still be that the dimples aren't fully formed. This is a common new builder error.

What tool are you using to do the dimpling?
 
I tried it with a Avery hand squeezer and then a main squeeze and c-frame. I tightened it to a point where there was some deflection in the yoke. If the rivet sits .007in below flush, is it really going to cause an issue during riveting? One would think the material will flex under the rivet set anyways. It seems to me it is pretty difficult to screw up a dimple with a hand squeezer. I cant imagine the squeezer set is improperly formed. Do the photos I posted seem abnormal from other builders experiences?
 
This thread has me doubting how well I've been dimpling, and questioning what is considered 'flush'.

what's a good way to measure how flush or not a rivet sits? Is it only applicable to after it's been set or before?

I just went and drilled/dimpled (with drdt2) a few scraps of .032 and the 426-3 and 426-4 rivets seemed to be recessed a bit before they were set, but once set, pretty well flush, but again, unsure of the best way to measure.
 
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Dimpling

Here are a couple of photos of some scrap .032 that has been dimpled, with the hole on the left slightly under-dimpled, and the hole on the right fully dimpled. The fully dimpled hole has sharper shoulders and the witness mark from the flat surface of the die around the hole is complete.
C-frame will give as good a dimple as anything if it is sitting on a firm surface... and hit as hard as you like.
The worst screw up of a dimple is a figure 8 hole if the die is not centred on the hole.
 

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