I need to know what happens to the shank of a 2117-T4 aluminum rivet
(1/4"D x 3/4"L) when it is peened.  My question is specific to 2117-T4
rivets, and I specifically need to know whether the shank expands
inside the hole of the the two pieces of metal I am joining.  The
hole is 0.265"D.  Will the 1/4" rivet expand
and fill-up the entire hole?

Hello stormo, I was interested in your question because I had never
considered the fact that a properly installed rivet of any material
would not expand and fill a properly sized hole. I first found this
very interesting web page that has much information on 2117T4 rivets:

http://www.rvproject.com/rivets.html

It does not directly answer your question, but has some very useful
info and suggests consulting MIL-R-47196A. I read this spec and can
now safely say that a 2117T4 rivet properly installed per this spec
will expand to fill the .265 hole. If it didn't, it would be
considered loose.

Here is the link to MIL-R-47196A:

http://home.flash.net/~gila/rivet_spec/rivet_a.htm

Here is the part that answers your question:

3.3.3.3 Peening. The driven rivet shall completely fill the hole.
Peening of the driven head by rolling the buckling bar shall not be
permitted since the rivet hole will not be filled.

This makes sense to me because any metal column does expand in
diameter when subjected to compressive forces. The only question I had
was whether the forces involved were sufficient to expand the rivet
enough to fill the hole. Your .265 diameter hole is the maximum
recommended diameter for a 1/4 inch rivet. Therefore, it will fill the
hole if properly installed. The only question remaining is if your
rivet length is correct. Your rivet should protrude through the hole
by 1 1/2 times the diameter or for a .250 diameter rivet that would
mean .375 inch.

I hope that this convinces you that your rivet will fill the hole.

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Request for Answer Clarification by stormo-ga on 02 Sep 2004 08:47 PDT

Thank you for your reply - there's a lot of information here. 
Regarding the military spec, I'm not sure that this is for a 2117 T4
rivet.  What makes you believe the 2117 T4 rivet would completely fill
the hole?  Do you know whether a 2117 T4 aluminum rivet solid or
tubular?

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Clarification of Answer by redhoss-ga on 02 Sep 2004 13:03 PDT

I just finished talking with several major rivet suppliers. It would
be very hard to obtain 2117-T4 rivets in anything other than solid.
You might be able to get a semi-tubular rivet in 2117-T4, but it would
be special order. If you were able to obtain such a rivet, it would
most certainly fill a properly sized hole when properly installed. I
would say that there is little chance that rivets you would use would
be anything other than solid. If your are interested in strength, you
would not want to use anything other than solid.
The MIL-R-47196A spec is for ALL rivets of ANY material. It is the
definitive spec for rivet installation for government applications.
There was much testing that went into writing this spec and we all
(taxpayers) paid for it. I am very familiar with MIL specs of all
types. MIL specs are the most stringent and hardest to comply with.
When MIL-R-47196A says that when a rivet is installed per that spec
will fill the hole, it will FILL THE HOLE. Therefore, all you must do
is follow the exact directions provided.

Clearly written and useful.

In science in school we do experiments. Why not do one to answer your own question?
Put that rivet into the holes and peen it to finish. Then get a
hacksaw, or just a hacksaw blade. Then cut off one of the heads of the
peened rivet with the hacksaw blade. Then eyeball, or use a magnifying
glass, the condition of the rivet shank inside the plate's hole.
Easy.