Cup set 1/8" out of shape?
 

Hello

I'm supporting two buddys during the start of their RV-7A project.

They showed me the first rivet results on the real parts ... ok, shop head looks very good, but what catch my eye was this: :eek:
Riveted with a pneumatic squeezer, not with a riveting-gun. The ring you can see on EVERY rivet.



The cupset is also pressing at the outisde of the rivet head. Ok, sometimes, when you hold it not absolutely perpendicular to the surface, you get a mark, but only about 1/4 of the diam. and not a full ring completely around!? On my plane and another buddys plane, we could not found such a ring on our rivets :confused:

This is what they are using:

Top row from left to right is a 3/32" & 1/8" cup sets; 1/8” modified cup set. The 3/32" cup set, we put them far away allready, before the start building. On a RV there is no 3/32" AN470 universal head rivet.

The rivet fits so far onto the cup set:


Now two questions:
- Build on, no replacemnt of the rivets?
- Redo with another cup set?
-Build on, but with a new rivet set?

For sure I will contact the manufactur of the cup set too.

Thanks for any inputs.

The snap is fine - the damage is due to slight lateral movement between the rivet and the snap. What is normally done is to put a small piece of masking tape on the riveting face of the snap, this increases the friction between the rivet and the tool so preventing the damage.

Edit: OK I see you are using a squeezer - I should have read this more carefully - I assumed it was with the rivet gun. Replace the die - it is the wrong size.

I have to say Doug, that is a fine explanation of what is happening, however, it does not answer the question, do I keep building or do I replace the rivits? I would say that these rivits are fine and I would keep going, (with the suggested corrective action, ie, tape on the snap) :)

must go thru a lot of masking tape at cessna.

Done with a pneumatic squeezer, not rivet gun!
 

These rivets are done with a pneumatic squeezer, not with a rivet gun.

The ring you can see on EVERY rivet.

My vote is to leave those rivets as is. I do not see any evidence of cracking on the factory head ,and the ring arround the factory head is very light. I do however sugest that you get another set for the next 15000 rivets if this bothers you.

Where did those sets come from?
Showing a concentric impression clearly made by a cup set that does not
seem to conform to a standard rivet head is not something I would continue to use.

Don't see any problems leaving what you have but
getting a new cup set as Arie suggested would be my choice as well.

If you are handy with a lathe you could simply polish out that step in that cup and your rivets will be fine.

I see no defect that would cause a rejection per this document -

http://www.vansaircraft.com/public/Specs.htm

However I would say the rivet sets are not shaped properly. I had one set that did this and just replaced them. The sharper edges will cause defects if the squeezer is not perfectly straight, a correctly rounded set will give you a little tolerance.

Just as a test case try setting a 1/8 rivet using the next larger set and see what sort of head is created. The Mil-Spec even allows for the use of two flat sets for an AN470 rivet.

The rings are not caused by something that will be solved using masking tape.
I have seen some (improperly made) rivet sets cause this, or (as already mentioned) the wrong sized rivet set was used.

I Agee. The rivets are fine and do not need to be replaced (doing so would likely cause much more of a problem.....)

The rivet set which came with my 2nd hand tail kit 20 years ago was like that. Ultimately, I bought a new set from either Cleaveland or Avery which eliminated the problem.