Separation During Riveting

agoessling · #1 05-05-2016, 12:28 AM

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:

az_gila · #2 05-05-2016, 01:05 AM

Is the .006 by the rivet body, or just at the edge of the rib flange?

salto · #3 05-05-2016, 04:44 AM

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.

StuBob · #4 05-05-2016, 05:47 AM

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.

Lionclaw · #5 05-05-2016, 05:48 AM

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.

dspender · #6 05-05-2016, 10:05 AM

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.

WAM120RV · #7 05-05-2016, 10:29 AM

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.

agoessling · #8 05-05-2016, 10:30 AM

Quote:

Originally Posted by az_gila

Is the .006 by the rivet body, or just at the edge of the rib flange?

It seems to extend to very close to the rivet shank.

Robin8er · #9 05-05-2016, 10:40 AM

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.

PilotRPI · #10 05-05-2016, 11:43 AM

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.