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Flush Countersink went Too Deep

MJarreau

Well Known Member
We were supposed to countersink for a flush rivet but went too deep by 0.010 in a part on the aileron hinge bracket that is 0.120. Should the part be replaced (again)?

Thanks,
Mike
 
Can you post a picture? My first thought is use the next size up river but that is just a guess at this point. How did you measure it to determine you were too deep?
 
What size rivet? Is this CS material the "top" part of the stack or will dimpled sheet metal? I'm not feeling a panic over 10 thou in 120 thou parent material. if the EDs, spacing are still good as they should be. If you're still feeling it, possibly consider some 1241 rivets (1/64" oversized). The raised head that gets hammered flat/stain hardened could help the appearance and immeasurably strengthen the joint. In a shear app, which rivets should be limited to, you aren't sacrificing any strength in bearing. All of this is predicated on the assumption that I'm understanding you correctly.
 
Is there any material left in the hole or is there a knife edge from the countersink to the hole. If the part is thick enough to not have a knife edge a countersink that is too deep is probably not too bad, but pictures would help.
 
Happens all the time

.010 deep in a .120 part should not be a concern at all. I don't know the part your riveting in detail, but I built a -4 and specialize in structures on heavy jets. If you have access to both sides, you can shoot a universal head rivet in the opposite direction and the bucktail will "fill" the countersink. Done and move on. Or, if your parts have edge distance to oversize, simply go the next diameter larger..plenty of material there. In fact you could probably leave the countersink you have, enlarge the hole, and shoot next larger rivet, then shave/sand the remaining rivet head material away.
 
.010 deep in a .120 part should not be a concern at all. I don't know the part your riveting in detail, but I built a -4 and specialize in structures on heavy jets. If you have access to both sides, you can shoot a universal head rivet in the opposite direction and the bucktail will "fill" the countersink. Done and move on. Or, if your parts have edge distance to oversize, simply go the next diameter larger..plenty of material there. In fact you could probably leave the countersink you have, enlarge the hole, and shoot next larger rivet, then shave/sand the remaining rivet head material away.

I agree with Bill, the part is salvageable. Both of his suggestions are valid ways of dealing with the issue.
A third one that I have used myself in the past is to make a thin spacer that can be put on top of the manufactured flush rivet head when you set the rivet. If you have access to a Whitney punch you can punch a small appropriate diameter spacer disk out of thin aluminum. The important thing is that if you set a rivet with the manufactured head in the counter sink that you have some method of assuring that the rivet head is held tightly to the bottom of the counter sink. What you don’t want to do is just install a rivet without using a spacer because the outer face of the rivet head will be flush with the surface of the part and there will be a void space underneath the Rivet head at the bottom of the counter sink.
 
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Is there space where you could drill another rivet hole? (but not closer than 2 diameters away)

Not debating you, Ralph but where did you hear that for spacing? The only minimum spacing reference I've ever found was 3D for U-heads and 4.5D min for CS.
 
I remember somewhere in the 43.13 where it calls out different edge requirements of standard and CS rivets, but I can't seem to find it now. Anyway, here's what I did find, and it does seem to support the 3D or 4D rivet spacing, it's just based on geometry though and not head styles.

"Rivet edge distance is defined as the distance from the center of the rivet hole to the nearest edge of the sheet. Rivet spacing is the distance from the center of the rivet hole to the center of the adjacent rivet hole. Unless structural deficiencies are suspected, the rivet spacing and edge distance should duplicate those of the original aircraft structure. If structural deficiencies are suspected, the following may be used in determining minimum edge distance and rivet spacing.

(1) For single row rivets, the edge distance should not be less than 2 times the diameter of the rivet and spacing should not be less than 3 times the diameter of the rivet.
(2) For double row rivets, the edge distance and spacing should not be less than the minimums shown in figure 4-5.
(3) For triple or multiple row rivets, the edge distance and spacing should not be less than the minimums shown in figure 4-5."
 

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Thanks for Your Time!

Can you post a picture?
Rocky, please see attached.

What size rivet? Is this CS material the "top" part of the stack...?
Scott, the rivet is a 4-x. Yes, the CS is on the top.

Is there space where you could drill another rivet hole?
Ralph, I don't think so.

... is there a knife edge....
Jeff, not even close.

... should not be a concern at all.
Bill, that's what my gut said, but we're trying to be careful and deliberate.

If you have access to both sides, you can shoot a universal head rivet in the opposite direction and the bucktail will "fill" the countersink.
Wow. Sounds ridiculously obvious and simple now that I see it in writing. To be honest, this never even occurred to us.

Or, if your parts have edge distance to oversize, simply go the next diameter larger..plenty of material there. In fact you could probably leave the countersink you have, enlarge the hole, and shoot next larger rivet, then shave/sand the remaining rivet head material away.
Bill, Again, wow. This is not something we would have come up with ourselves, but sounds elegant. We have not measured the dimensions, but believe this would also work.

A third one that I have used myself in the past is to make a fin spacer that can be put on top of the manufactured flush rivet head when you set the rivet.
Scott, We had thought of that but lack the tools, and probably skills to do this one.

Bill, Would the universal rivet be the same length as originally called out in the plans?

We are humbly grateful for your thoughts and, more importantly, the time you've given to consider this!

Cheers!
Mike
 
Pics for Previous Post

Please see attached......

Oops.

Mike
 

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The pix make it look worse than 10 thou. If it were me:

If I could verify 4.5D available pitch and proper ED for AD5s, I'd probably do it. CS to the new required depth or shave the head once installed like fixnflyguy said.

Additionally, I'd procure some 1241 and 1097 rivets (1/64th and 1/32 OS). This will save other future sins.

I'd familiarize myself with lisi aerospace HI-LOK fasteners. They have a very wide variety of one-sided fasteners that incorporate different head styles, materials, shank sizes/oversizes, etc. General Aircraft Hardware can order them for us civilian types. These are a very under appreciated, under utilized product IMO. Expensive but not compared to new product/shipping/rework.

The aforementioned can really make a lot of "Oh-F*^s" both salvageable and at least as safe as the plans if proper guidelines are followed.

Just a thought. You'll hear many.
 
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