Earlier, Stealth Pilot wrote:

...place the rivet hammer on it and pull the trigger...

The way I read Max's question, he wants to build a machine for
squeezing rivets, not hammering them. That's why I responded as I did
in this post:

http://groups.google.com/groups?dq=&...g.googl e.com

(use cut-and-paste if the newsreader breaks the link into multiple
lines)

Of course, I could have just misread or misunderstood Max's post. My
apologies to all if so.

Personally, I prefer to squeeze rivets whenever possible, and only
hammer them when squeezing is impractical. What I found while riveting
the HP box spars is that it is possible to squeeze the rivets using an
elaborate set of jigs, rams, and cradles. But the job just went faster
when I went ahead and hammered them with my horseshoe-handled 5x. Less
pleasant, yes, but faster.

And, while I'm on the topic, I just noticed my basic conceptual error
in my earlier post cited above: squeezing rivets to a given shop head
diameter requires a specific force, not a pressure (which is force
exerted over an area). However, that force induces a pressure in the
rivet material, since the force required is related to the
cross-sectional area of the shop head. Let's have a bit of a look at
that.

But first, a bit of a warning:

*** Warning: I'm not an engineer, and what follows is not engineering
advice. It is rather more of a tentative application of high school
physics to data found in the Aircraft Spruce catalog. ***

Going back to my earlier assertion that it takes about 2750 lbs to set
an AD4 rivet, we can compare that with the .025 in^2 area of a .18"
dia shop head, and see that the pressure on the shop head is 2750/.025
= ~110000 psi, or about 3 times the 38000 psi tensile strength of the
rivet material. That does sound a bit high, so I begin to doubt my
memory about how much pressure I had to put behind the 1" dia. ram
piston I was using. However, I am confident in my memory that the
pressure _was_ on the high side of a 3000 psi pressure gauge; and I'm
pretty sure that the guage was accurate to within about 5%.

As a for-example, if I was pumping the ram to only 2000 psi to set
rivets, the force exerted by the 1" dia piston would have been
pi*(.5"^2)*2000 = 1571 lbs. If that's the case, the pressure on the
..18" dia shop head would have been 1571/.025" = ~63000 psi, or about
1.65 times the tensile strength of the rivet material. Somehow that
sounds like a more reasonable number. Probably the truth lies between
the two values.

Anyhow, based on my experience using hydraulics cobbed together from
broken bottle jacks, it's an easy enough thing to test.

Sorry for rambling so, and best regards to all

Bob K.
http://www.hpaircraft.com/hp-24