CharlieWaffles

CharlieWaffles

Well Known Member
So I was looking over the Rivet Mil-Spec http://www.vansaircraft.com/public/Specs.htm specifically 3.3.1 which says "3.3.1 Cleaning mating surfaces. Before parts are riveted together, all chips, burrs and foreign material shall be removed from the mating surfaces. Burrs may be removed from rivet holes by chamfering to a depth not to exceed 10 percent of the stock thickness, or 0.032 inch, whichever is less. Disassembly after drilling and before riveting, in order to deburr faying surfaces, shall not be required."

Does that mean when we disassemble, that we dont need to debur the mating surfaces and only need to do the "outside" non-facing surfaces? To date I've "both" sides of a hole after drilling.
 
The mil-spec certainly does appear to indicate that. However, I can tell you that in the large aircraft manufacturing world, entire wing skins (large, heavy, and cumbersome) are removed by overhead crane after drilling to debur the mating surfaces. The specs of a certain US-based aircraft manufacturer, not to be named, indicate that if two pieces are tightly clamped together when drilled, then the faying surfaces do not need to be deburred. Clecos, however, are not considered clamps for this purpose. In practice the only time faying surfaces are not deburred is when they physically cannot be separated.

I have been disassembling to debur faying surfaces on my 9A, and I will continue to do so. As much of a PITA as it is.....
 
there are some on here that skip deburring altogether, and I don't see them falling out of the sky.....

to each his own, most of these planes are hangared and fly 100hrs a year at most, it would take a long time for the lack of proper deburring to show it's face

disclaimer: this is based on what i've read/learned, not on first hand experience, i have no idea what i'm talking about and i'm subject to correction :D
 
Yep, but I deburr it anyway--not sure why other than when I deburr holes I pretty much turn into a robot. FWIW, this is real obvious in wood working. Drill through 2 pieces of wood and the interior holes where the two pieces meet will be nice and smooth but the exit hole (particularly with plywood) will have tearout. If that's an issue, the solution is to either add an additional piece of wood as a backer when drilling or to flip the 2nd piece over so whatever side is the "exterior" of the finished part is on the "interior" for drilling (geometry doesn't support this option very often).
 
From Isham - planetools

On the practice kit, I de-burred with a de-burring tool, making sure to take away as little material as possible, and then dimpled the 426 3-3 holes. When I started riveting, the clecos just popped right out. In my tool instruction manual, here's what they say about that;

Deburring.jpg


Cheers
 
Kobwo said:
On the practice kit, I de-burred with a de-burring tool, making sure to take away as little material as possible, and then dimpled the 426 3-3 holes. When I started riveting, the clecos just popped right out. Cheers
Click to expand...

I don't think it's due to deburring, and here's why I think that.

I helped my buddy build his -8, and throughout the *entire* build, we never had a cleco just "pop" out. We deburred *everything*, both sides of every hole.

For the empennage on my -7A, same thing. Never once did a cleco come out.

Got to the wings on mine, and I wanted to use more clecos for some reason I remember, so I asked another builder friend if I could borrow a few hundred of his. No problem...except...THOSE clecos have a distinct tendency NOT to stay in dimpled holes. They don't even "pop out" sometimes, they just *fall* out. I call them his K-mart Clecos. (And yes, I can tell the difference because -8 owner's clecos are *well* used, while the borrowed ones were used on a QB fuse and wings, and are nice and shiny and practically new). I think the brands are even different.

I *know* I'm not over-deburring, nor doing anything else that isn't acceptable. It's the clecos. The K-mart Clecos work just fine on non-dimpled holes, but I'd say a good 15-20% of them won't stay in a dimpled hole.

No, I didn't put a mic on them to analyze further why they do that :)
 
All clecos are NOT created equal....

Flying Scotsman said:
....It's the clecos...
Click to expand...
The Flying Scotsman accurately summed up your problem with three little words..."It's the clecos." Good clecos will grip and hold quite well, even in dimpled holes. Other worn or lesser quality clecos will fall or pop out of the very same holes. Consider this: During the first engine runs, the forward upper skin on my -6A was 100% clecoed into place. If you ever clecoed that skin into place, you KNOW firsthand how much of a spring load is on it. In my case, and as the photo shows, not one single cleco popped out during those engine runs. Don't try that one using worn or lesser quality clecos.

xgcdpy.jpg


For those builders with a bunch of clecos that just won't hold, here is a very simple old school way to get them to grip like new:

http://www.vansairforce.com/community/showthread.php?t=57503
 
The Clecos that I'm using are ClekoLoc - U.S.A. They are brand new and I used them for the first time this week. They seem to be a quality Cleco to me.

My point was what my tool supplier said in their instructions about de-burring.

DSC_0032.jpg


Cheers
 
Two words: stress relief.
Many years ago I fabricated some aluminum boxes using a brake. They were a work of art, and I was very pleased with myself. Imagine my dismay when a couple of them cracked after after the last bend. A careful inspection revealed that I had failed to properly deburr them before the bends! :(

Take your time, do it right,
might save your life,
some dark and stormy flight. :)
 
Kobwo said:
The Clecos that I'm using are ClekoLoc - U.S.A. They are brand new and I used them for the first time this week. They seem to be a quality Cleco to me.

Cheers
Click to expand...

I'll compare the "good" clecos with the K-mart clecos when I get home, but just as here, the ones that won't hold are nice and shiny and look brand-spanking new (since the person who used those did a quickbuild fuse and wings, they probably weren't used very much in comparison to two slow-build kits).

The point about over-deburring is well taken, though...just a quick turn or two usually does the trick. We're not countersinking here :).
 
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I have my clecoes divided up into two batches ( and marked of course). The ones that are too loose and pop out of finished and dimpled holes are just the ticket for clecoing together the "as punched" holes where the others are too tight.
 
William Slaughter said:
I have my clecoes divided up into two batches ( and marked of course). The ones that are too loose and pop out of finished and dimpled holes are just the ticket for clecoing together the "as punched" holes where the others are too tight.
Click to expand...


Good idea. I'm going to roll with that.

Cheers
 
The main reason for deburring in production aircraft is for fatigue life. If you leave the burrs there and then buck a rivet or install a bolt, the sharp edged pieces of metal will be driven into the nearby metal, causing small stress concentrations. Over time they will develop cracks. That's also part of the reason why you don't see many blind rivets. One sided drilling without deburring and then installing a blind rivet is very very fast, but creates very low fatigue life for a bunch of reasons
 
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