Pounded Some Access Panel Nut Plate Rivets

As I mentioned in the previous post, the "act" of setting rivets turns into an artistic, creative adventure that involves trying to figure out how to clamp and secure very odd-shaped parts. I had to dig into my stash supply of wood to come up with an acceptable method for doing so. The pics that follow show how this was done. The basic problem was trying to setup the subskin in such a way that it allowed me handle the rivet squeezer and the part at the same time with both hands. i had to get the subskin at the right height compared to the surrounding wood clamps so that both sides of the squeezer would fit on either side of the subskin without interfering with the wood or the clamps.

The best method I have found for this, mostly since the squeezer is such a damn heavy tool, is to secure the part so that I can use my left hand to steady the yoke and rivet set against the manufactured rivet head so that I know that it is flush with the skin, and hold the squeezer in my right hand. To do this, I have to make sure that the clamping method both secures the skin so that it will not move when I apply the squeezer, and at the same time the clamping solution has to allow enough room for the big-ass squeezer body on the other side of the skin. This is not an easy task when dealing with pre-bent skins, but can be done successfully if you put enough time and thought into how to do this correctly.

For tools I used the pneumatic squeezer with air pressure set to 90 psi, and I used the flange yoke to allow it to fit inside the access panel hole and fit the rivet set as easily as possible. I also used 2 1/2 inch x 1/8 inch flat rivet sets on the top and bottom of the yoke.

This first pic is my initial clamping setup to start setting the bottom row of nut plates. Note the mixture of wood pieces I had to use. I was too lazy to trim the wood to exacting sizes. I just worked with what I had available. This side has enough clearance for the rivet set on the top end of the yoke on the squeezer, so that the rivet set can be centered on the manufactured head of the rivet.

And the back side, which had to be somewhat lower than the other side to allow room for the squeezer body:

Notice how I used the end-piece of each clamp on this side, once again to allow as much room for the squeezer body as possible so that it will no interfere with the clamps. I have screwed up more than one rivet in the past because the squeezer ends up hitting either a clamp, the part, or some wood, while in the process of squeezing the rivet. This is why you spend more time setting up the clamping solution than setting the rivets. Some people my even consider this a "simple" operation and probably would have held the part in their hands to set the rivets. Not me. This is always a time consuming, agonizing process for me, but the outcome usually justifies the means for me, since I usually do not have to reset very many rivets after taking the time to set this up correctly.

The next pics show the setup for each nut plate. One cleco on one side and the NAS 1097 3.5 rivet in the other hole:

And here is a pic of the Squeezer setup. The other thing you have to do is adjust the ram of the squeezer so that it sets the rivet properly so that the shop head is 1.5 x the diameter of the rivet shaft, and has the proper height, etc. the very first rivet is always an experiment, unless you take the time to setup a practice piece with all the same dimensions as the actual part, so you can set it up that way. Otherwise, what I usually do is take a rivet and then activate and hold the squeezer in its compressed state, and place the rivet next to the rivet set to determine if the gap is correct or not. I usually start so that the rivet will not set quite all the way at first. Then I will set the rivet and note the result, and then readjust the ram height accordingly and re-squeeze the rivet one or tow more times until the squeezer is set exactly as it should be for the remaining rivets. In other words, I "creep" up on the proper setting of the ram. Better to be too shallow at first than too close with the ram.

Next is the hard part of setting the rivet. I don't have enough hands to hold a camera and perform the operation at the same time, so all you get here is the aftermath. One properly set rivet down, several more to go. the trick for this with nut plates is making sure that the rivet set will clear the screw shaft of the nut plate, and still make full, flat contact with the rivet shaft so that the shop head is formed nice and flat against the nut plate flange. This is where the heavy squeezer and sometimes awkward positioning of the squeezer make this feat next to impossible sometimes.

So you position the top of the yoke against the manufactured head, hold that part of the yoke against the skin and apply a little pressure with your left hand, and position the squeezer with your right hand so that the rivet set is perfectly perpendicular with the rivet shaft. Then you hit the trigger and pray that it all comes out good. Centering the rivet set against the manufactured head is always the challenge.

As a footnote, you always have better control during the entire squeezing operation by using a hand squeezer instead of the standard pneumatic one. The only way that this tool would have worked in this situation is by positioning it so that the flat rivet set against the manufactured head would have been on the moving ram, and this is just something I try to avoid at all costs, because it is tricky at best to try to keep the rivet set on the end of a moving ram in place without it moving somewhat. The handles would not fit in between the curved skins, which it what I needed in order to make the hand squeezer work the way that I would want it to.

And after the second rivet is set, you get this blurry pic:

And the other side

And here is a rare pic of yours truly performing the positioning exercise previously described/ You'll need to note that I have turned the part around and rearranged the clamps and wood blocks to allow riveting the nut plates along the remaining edges. Like I said - you have to get creative sometimes:

And here are the results after the job was "done." Truth be told, even after all this prep, I ended up with about 5 rivets that I was not happy with. Three of them I was able to "coax" into position with a punch and hammer to get the manufactured head to sit a bit more flush against the skin than they turned out with the squeezer. It was that perception problem I described earlier where, despite your best efforts, sometimes you just can't tell very easily if the rivet set is flush and flat against the skin, and you end up with a slightly raised rivet head. Flush rivets need to be just that - flush - against the skin. So you either drill them out and reset them or sometimes you can pound them a little to force them further down into the countersunk hole.

I have no choice but to reset the other two rivets because one of them was inserted into the wrong rivet hole, and the other one was a 1097 rivet inserted into that one hole that mentioned in previous posts that I had to countersink for the larger AN426AD3.5 rivet. IOW I put the smaller rivet head in the hole with the larger countersink, so that one has to be drilled out and replaced with the correct rivet.

 After all the rivets were set, I wanted to pre-set the #8 screws into each nut plate. I took some Boe lube ad ran the threads of each screw into that to coat them with this lubricant. I did this in lieu of taking a tap and running that through each nut plate. There is a lot of discussion about this on the forums. The problem is that all nut plates are set to be very very tight, and this is by design. Unfortunately, this makes it very hard to turn the screws.

The rule is:

If it is a structural or otherwise crucial attachment that requires a specific torque or must remain tight for structural reasons, you do NOT run a tap through the nut plate. Instead, the preferred method is to use a lubricant like Boe lube on the screw threads, and this does a great job of allowing the screws to be threaded onto the nut plate much easier, without compromising gripping strength.

Otherwise if there are no structural concerns, such as for access panels or floor boards or other compartments, you can run a tap through the nut plate if you wish. Just know that this effectively removes par of the threads in the nut plate and re-forms and loosens the hole just. SO pick your poison and realize the consequences.

All the screws went on as expected, and even with some of my less-than-perfect rivets, the access panel fits nice and flat up against the subskin, so I was happy about that.

Next steps are to drill out and reset those two remaining rivets, and then scuff, clean and prime the patch plate and the access panel.Then I dimple the ribs and the outer skin and figure out what to do about the wallowed out holes in the outer LE skin. I plan to call Vans about that on Monday because I just discovered that I have some AN426AD-4 1/8 inch rivets that I think I can use in those first couple of holes if the outer skin is too messed up for a -3 rivet.

Pounding rivets was challenging but fun. Only about 12,000 more to go.......

KPR