Frustrated: Squeezer bending rivets
 

I'm most of the way through my empennage and I'm still struggling to get my squeezer to to not pull the shop heads as they set. Biasing the tail towards the throat side of the sets seems to help but its not always possible to make that happen because the nose of the yoke inevitably hits the web of whatever is being riveted (see photo).




Normally I would set the rivet with the yoke perpendicular to the spar (as in the photo) but I also tried a two step set process where I'd hold the squeezer as parallel to the spar as I could for half a squeeze (with the yoke to the right), then finish the squeeze with the yoke to the left all in the name of trying to get an axial squeeze. That helped a little, but still not as good as I think it it can be.

I've also played with some rotating motion of the squeezer body as I set to compensate for any yoke flex. Most of my work is with a 3" yoke and I am very deliberate in my process with alignment and trigger work. With a 4" no hole yoke, this behavior gets even worse. I am also using the quick change pins, and these have a very, very small amount of play in them.

I'm really frustrated that after most of the empennage I still don't have that confidence that when I pull the trigger, I'll get a great rivet every time, which is my expectation. :mad:Perhaps that expectation is too lofty...
Just tonight working on the left elevator trim tab attachment spar, I had to redo more than 50% of my rivets, some more than once. That kind of efficiency is unacceptable.

Is it worth grinding down the nose of the yoke a little bit to be able to reach deeper?

Those shop heads look pretty darn good to me, from what I can tell. Fwiw, I did grind down the nose of my 3” yoke a bit

I would guess that the yoke is deforming slightly. A beefier deep yoke or a yoke with a shorter throat will reduce/eliminate that.

I have two hand squeezers. The one with the 1.5" yoke makes perfect shop heads. The 3" yoke deflects some and doesn't produce "plumb" shop heads.

Yoke
 

Agreed. The shop heads look good. Always choose the shallowest yoke for the job and use the thickest set possible on the shop side.
OR, get really comfortable with gun and bar. Lots of places on the plane where a squeezer won't work. If fact, quite a few where you need a double offset.

And I agree as well. The shop heads in the photos are fine.
Some deep throat squeezer yokes flex more than others causing the faces of the rivet sets to mis-align slightly which will cause the shop head to vary in thickness slightly.
As long as the head is still centered and the thinner side of the shop head is not thinner than the MIL Spec requirement (none of yours look anywhere close to being too thin) then they are fine.

Yep them rivets look pretty dang good. When I was new to the squeezer I remember this too, when squeezing I find that focusing the vast majority of my attention to get the rivet in the center of the set on the yolk helps a lot.

I can always trust the VAF community to put me at ease! The pancakes (shopheads) are nice and even, they just happen to be setting slightly to one side (always toward the flange edge in my case), enough that I've been hemming and hawing on whether they should stay or go.

I decided that I would nibble away at some of the material on the tip of the yoke to help my cause. Being able to position the rivet closer to inboard edge of the set helps alleviate the lateral force that seems to pull the shop head toward the throat of the yoke.

A couple of layers of Duck tape on the face of the yoke would not go amiss.......

+1 on trimming the yokes when necessary
 

I have found that I can use my flange yoke for a large number of rivet squeezing tasks to the point that I prefer that yoke whenever possible. it has about a 2 inch clearance but also has extended set inserts on both ends of the yoke that allow the sets to get over and under the flange and down on both ends of the rivet. It works especially well when you have hinges jutting outward from the rest of the flange because it provides enough clearance from the hinge rungs and a short enough moment to keep it from flexing any more than any other yoke IMHO.

That said, I currently own three separate yokes, and I have ground down the fronts of each and everyone of them to address the clearance issue against the web of the part just as you show in your pics. I have even had to slightly grind down a few rivet sets along the way for exactly the same reason.

I also agree that your rivets look good to me. So grind down those yokes a bit to get the clearance from the web that you need and KPR. If corrosion is an issue where you live (it's not for me) then spray some primer on the exposed metal afterward. You will get over the "sinking" feeling of potentially "ruining" a fairly expensive hunk of metal (the yoke) after you grind it down and then use it successfully to set another quality rivet. From then on you won't even think twice about modifying some of the tools as you progress, as long as you do some testing with it before you apply it to the real thing, just to be certain that it will do the job correctly.

When I first started on my RV-10 emp kit, I had similar problems with my squeezer, while building the first piece (vertical stabilizer). Turns out the adjustable set holder (i.e. the part that actuates) was bent. Here's what I did:

I removed my adjustable set holder piece and chucked it into my drill press and spun it up. It was easy to see that it was in fact bent. My tools were ordered as part of an Isham Tools RV kit (planetools.com), so I called and they replaced it free of charge. This helped solve my issue.

Bonus Tip: When using the squeezer, I always make sure that more pressure is on the factory head side of the rivet, just like when bucking rivets with a rivet gun. It's the same, whether or not it's a flush or universal rivet. Always push harder on the factory head side. It helps keep the rivet in place while it's mushing and you'll end up with a nice round shop head. Keep practicing. I'd never build an RV without a pneumatic squeezer.