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Separation During Riveting

A

agoessling

I'm New Here
I was riveting some of the HS ribs to the spar this evening and ran into some separation issues. The rib flange sat flush with the rivet in place before riveting. It also sat flush after giving it a few taps to swell the shank. However when I went to fully form the shop head, the rib flange pulled away from the spar ~0.006". These were some of my better rivets in terms of the quality of the shop and manufactured head, but twice I had the same separation problem. I read that too low pressure can be a cause of this so I increased the pressure on the mini-regulator until it was just on the edge of controllable for me (Here the rivet was being set in less than or equal to one second). This seemed like it might have slightly improved the separation distance, but not enough. I would have liked to put the manufactured head on the rib flange but that would require an offset set so I put it on the spar.

Any ideas what might be causing this or how I can improve it? Should I replace?

Images below:

5arlud.jpg

o7tuvq.jpg
 
I had this problem with a couple of rivets and I found where the rivet didn't slide in smoothly ie I had to jiggle the part resulting in the flange for instance resting back on the rivet making it tight, when I pulsed the riveter the flange jacked itself up the rivet slightly. By making sure the rivet wasn't a force fit the issue resolved itself. A slight touch with the drill is all that's needed to ensure the rivet goes in smoothly.
 
I'm a fellow newbie, so ignore me. But.....

That gap is the reason I've been trying to put the manufactured heads on the rib side. That way the pressure you apply to the set before pulling the trigger compresses the pieces together instead of apart.

I think what happens is the rib bounces when the rivet gun is on the spar side and the rivet catches it mid-bounce. That first whack moves the rib off the spar and simultaneously thickens the rivet so the rib can't bounce back.
 
Unless the plans say otherwise for a given location, you'll want to put the manufactured head of the rivet on the side with the thinner part.
 
I believe placing the manufactured head on the thicker side is best. I also believe early on I was driving with too much force. This problem shows up more on thin pieces. I think driving the manufactured head on thin metal can tend to create a ditch for the rivet bending up the thinner metal around this ditch.
 
UK

In the UK a gap above 2 though would lead to the part being rejected. I was taught to draw up the mating parts when riveting. One way of doing this is pressure on both sides of the parts being joined.

The second way is when setting a rivet is to give it a light squeeze so it swells into the hole, or a light tap with the gun, then place a nut on the shop side and again a light tap with the gun or squeezer on the nut to draw the parts together.

Then hit it with more power to set it.

Of course you need nut big enough to accommodate the shop head. With the ones shown I would try this first being careful not to over set the rivet, before I considered replacing the rivet.
 
two things-

1) The reason it separates is because the pieces aren't flush when you begin riveting. If there is a gap prior to setting the rivet, the gap will stay there and possibly even get worse when you set the rivet.

2) rivets expand, so if you put the shop end on the thin side, you will expand and possibly crack the thin part. Always put the manufactured side on the thinnest side, the only exception being when it it physically impossible to fit the rivet gun to make that happen.
 
I've found this on the practice kit as well. Usually at a corner, as in your case. For corner rivets, even when parts initially sit flush, I'll cut some vinyl tubing just longer than the rivet. Partially set the rivet, remove the tubing, then finish the rivet. Keeps it nice and tight.

Of course that only helps if you know which rivets will do that before you rivet. Sometimes I'll have to drill out, then use the tubing trick if it is misbehaving.
 
agoessling said:
It seems to extend to very close to the rivet shank.
Click to expand...

Then it probably should be a reject. The US mil-spec follows the numbers given by WAM

g. Sheet separation after riveting which allows a 0.002 inch feeler gage to be inserted between sheets from any direction far enough to touch rivet shank (see Figures 1G and 1H).

Try the "make sure the rivet slides in" approach of post #3
 
Draw pieces together

When I was taught how to rivet by an ex-SR71 structural engineer, he showed me how to use a special bucking bar that had a hole in it. The rivet was inserted into the part and then into the hole in this bucking bar, and Zapped a few times. Then the bucking bar was turned over and the rivet was set. I never really understood why this was done, but now I surmise that the first step probably drew both pieces tightly together.
 
Vinyl tubing, or an O ring of just the right size, over tbe shank prior to riveting. If you can arrange to back-rivet, most back-rivet tools will apply pressure to the work piece to push them together before riveting.
 
Way to go Bob! I was beginning to think that the 'just add water' kits had driven all the old hands off the list.

Tubing, o-rings, or my favorite, neoprene/other stiff rubber sheet, just thicker than the length of the exposed shank. I used garden hose washers for a lot of this work. Cut a piece a convenient size, and drill a hole near the edge using a bit the same size as the rivet diameter. The hole will close up after drilling; that's a good thing. Insert the rivet; apply the rubber sheet over the exposed shank (it will grab & hold the shank, keeping the rivet in place). Drive with a short burst; remove the rubber. Complete the driving process.

AC43 will recommend where to put the factory head for thick/thin assys.

Charlie
 
Separation during riveting

During my 7 build I was shown a method used by Boeing riveters (rumor) about using apiece of lead over the shank of the rivet then use a bucking bar, the lead compressed the parts before the rivet set, sure makes it easier.

RV7
KEith Rhea
 
PilotjohnS said:
When I was taught how to rivet by an ex-SR71 structural engineer, he showed me how to use a special bucking bar that had a hole in it. The rivet was inserted into the part and then into the hole in this bucking bar, and Zapped a few times. Then the bucking bar was turned over and the rivet was set. I never really understood why this was done, but now I surmise that the first step probably drew both pieces tightly together.
Click to expand...

I like this tip.
 
Just another quick method to draw to pieces together:

-If two pieces aren't exactly flush against another you can lightly set the the rivet, then move your bucking bar adjacent to the rivet and again lightly tap the rivet with the gun, which will pull the piece down the partially set rivet. Once the pieces are together you can just finish setting the rivet.
 
What does that mean?

Use a washer/piece of rubber/etc? Is this done so that the bar then strikes the rivet but simultaneously pushes the flange to the spar? TIA

Still learning how to use my hands,
Mike
 
MJarreau said:
Use a washer/piece of rubber/etc? Is this done so that the bar then strikes the rivet but simultaneously pushes the flange to the spar? TIA

Still learning how to use my hands,
Mike
Click to expand...

Its essentially combining the two step approach I mentioned into one.
 
MJarreau said:
Use a washer/piece of rubber/etc? Is this done so that the bar then strikes the rivet but simultaneously pushes the flange to the spar? TIA

Still learning how to use my hands,
Mike
Click to expand...

The rubber should be *slightly* thicker than the exposed length of the rivet, in the assembly. With the bar against the rubber and over the rivet tip (the tip of the rivet will be almost touching the bar), drive with a short burst of the gun. The rubber, captured between flange and bar, will force the 2 flanges together when the gun strikes the rivet head. As the rubber compresses after forcing the flanges together, the bar will contact the tip of the rivet and begin to set the rivet, expanding it in the hole and locking the flanges while they are held together by the bar-rubber-flanges-rivet factory head-set stack.

Remove the rubber sheet and finish driving the rivet.

With softer rubber sheet, you could finish driving before removing the rubber, but it will last longer (more rivets) if you remove it prior to fully setting the rivet.

Do it once on a couple of scraps, and it will be instantly obvious what's happening.

Charlie
 
Separation of Parts While Riveting

If I understand the problem correctly, a simple solution that has worked for me to keep two parts together while riveting is to put a small rubber grommet (inside diameter of the grommet the same size of the rivet: example 1/8" ID grommet for an AD4 rivet) on the shop side of the rivet. Hold the bucking bar against the grommet. While shooting the rivet, the grommet will force the two parts together as the rivet sets and will generally just fall off after being shot, or is easily removed. The gap will usually be eliminated.

Hope this helps.
 
Makes sense, now....

Thanks, Charlie and Vantastic12. I thought that was the case....

Best regards,
Michael
 
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