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To deburr, or not to deburr

2

2bolts

Well Known Member
I'm working on my tail unit, and am currently at one of the burr and edge stages.

My question is this.

The plans say to edge and 'deburr all'. I assume this includes rivet holes as I was taught on the RV Assembly course. But unless I am mis-reading/understanding my mechanics manual, it suggests not to burr holes that are going to be dimpled, such as rivet holes. My instinct is to deburr the rivet holes.

Thoughts?

Opps just noticed title should've been 'To deburr, or not to deburr'
 
Deburr everything...rivet holes, tooling holes, lightening holes, edges, notches, flanges...

In fact, a hole that is going to be dimpled is going to be stretched, which I would think would *increase* the risk of a crack if not properly deburred.
 
I read the very same thing back a few years ago when I started but deburred everything anyway. I never got an explanation on why it said that.:confused:
 
The deburring reduces the risk of cracking, particularly fatigue related cracks originating at stress risers. Best practice is to only dimple cleaned, deburred holes, since doing otherwise could embed bits of burr into the surrounding metal.
 
Deburr

I keep an assortment of drill bits , long short and different diameters on the work bench for deburing holes . Wrap some masking tape around the bits so they are easy to grip without wearing out your fingers . Deburing tools with a swivel blade is great for the lightening size hole or any hole larger than a half inch. I debur everything completely smooth ,it's part of my therapy.
 
Thanks everyone

I'll deburr.

Thanks for the reamers idea Rockwoodrv9, I'll have a look at them.

Thanks az_gila for the link

And thanks to the whomever for correcting the title.
 
My cousin used to work for one of the giant aerospace companies making helicopters for the military. He claims that all they did was use a chip chaser to remove the debris from the drilled sheet and then riveted them together. No deburring at all.

I didn't specifically ask him about CS or dimpled parts.

I suspect that very few spam cans ever saw a deburring operation, but I could be way off. Anyone care to chime in?

Van's mentions somewhere that a Roloc disc works well and is very fast. However, if you're gonna polish the plane, don't use it on the outside!
 
rockwoodrv9 said:
Use a reamer for the drilled holes and save a bunch of time.
http://www.cleavelandtool.com/prodinfo.asp?number=RSF40
Click to expand...

I too use reamers on pre-punched holes in assembly to acheive the final hole diameter, but I've found that doesn't negate the need for deburriing. Even reamers leave a bit of a burr, especially on the inside. One turn with a deburring bit on a speed handle usually does the trick. I only wish edges were so easy...
 
Just to throw a grenade in the room.....I have been told recently of some engineering studies that tested typical RV-style material with holes that had been deburred and not debured, then dimpled. These were high-cycle fatigue tests designed to create cracking. From what I was told by fairly reliable sources, there was no difference between holes that were deburred and those that weren't - in fact, the only signs of cracking seemed to begin at the circle that would have been the outer edge of the dimple die.

I don't have any supporting data to back that up - just passing on what would be considered hear-say evidence in a curt of law - but the sources were pretty good.

Does anyone have documented evidence of cracks being seen on non-deburred holes?

Before anyone wonders, we always debur holes in my shop...at least we have up until now! ;)

Paul
 
It is my understanding that deburring drilled holes is to ensure the riveted sheet-sheet joint is tight. Since you are only removing the burr on the outside of the sheet, I don't see how you are removing any cracks "in" the hole. If you drilled a hole in 1/4" plate, how would you "deburr" that hole? Ream it if you need a very precise, smooth bore, but otherwise leave in the drilled condition and remove any burr on the entrance/exit.

The shop answer is to deburr all holes lest ye leave more DNA on the project.
 
fl-mike said:
It is my understanding that deburring drilled holes is to ensure the riveted sheet-sheet joint is tight. Since you are only removing the burr on the outside of the sheet, I don't see how you are removing any cracks "in" the hole. If you drilled a hole in 1/4" plate, how would you "deburr" that hole? Ream it if you need a very precise, smooth bore, but otherwise leave in the drilled condition and remove any burr on the entrance/exit.

The shop answer is to deburr all holes lest ye leave more DNA on the project.
Click to expand...

I agree - If you read the rivet spec., the only reason for deburring is to get the sheets to "sit" together with no gaps before riveting.

It specifically says that a stack of material does not have to be taken apart if it was tightly clamped when drilling.

Moving into a never-ending debate -- :) -- my observation is that a fully cured epoxy primer layer, such as the AKZO primer, helps prevent burrs if you use a nice sharp drill. This makes sense since the outer primer layer would be much harder that the Alclad pure soft aluminum surface of the unprimed material.
 
I deburr everything as others have said. I have several deburring tools. The tool that I have used the most is this tool from Cleaveland Tool: http://www.cleavelandtool.com/prodinfo.asp?number=DB04. With a battery operated screwdriver and this bit I'm able to quickly deburr the many holes that need deburring. I have an old Black and Decker battery operated screwdriver so I'm sure you could do even better with a newer screwdriver. If you want cheap I think Harbor Freight had one for about $8.
 
i *really* like my Cogsdill Burraway tools...I have a bunch of different sizes, but sadly I bent both my #40 and #30 sizes a while back when the drill fell over (you'd think I'd learn after the first time :( ).

Makes quick work of deburring holes, and particularly useful when deburring holes in assembled parts (like the fuse) where the other side is a pain to get to...
 
Ironflight said:
Just to throw a grenade in the room.....I have been told recently of some engineering studies that tested typical RV-style material with holes that had been deburred and not debured, then dimpled. These were high-cycle fatigue tests designed to create cracking. From what I was told by fairly reliable sources, there was no difference between holes that were deburred and those that weren't - in fact, the only signs of cracking seemed to begin at the circle that would have been the outer edge of the dimple die.
Click to expand...

When I upacked Isham's tools there were istructions there which said something like "it is not necessary to make a perfect hole". I don't have it with me to quote.
I think is is intersesting they mention this. I also think is that the idea is not to drive yourself nuts with this.
 
The factory holes are punched , one side of your part has more to deburr than the other . It will only add a few hours to your total slow build to deburr every hole , both sides . The amount of time wasted trying to fix a rivet that is sitting wrong due to a burr is not worth not doing it .
 
Cracks

I'm not sure if this is relevant to the conversation as I think the discussion is primarily regarding the #30 and #40 holes.

I did experience cracking in the dimples when dimpling .032 for the no 8 screws in the tanks. Fortunately I read others had experienced this difficulty before dimpling the tank skin so I did not end up with a skin full of cracks.

Based upon my very unscientific testing I suspected the cracking was primarily a function of my crisp spring back dimple dies. The problem was exacerbated if the holes were not deburred properly. All cracks emanated from the edge of the hole. I suspect this problem might not exist if using a cheap set of import dies. Since I didn't have a cheap set of dies in the shop I was not able to test this theory.

Try dimpling some .032 for a no 8 screw and see if you experience cracking.
 
It's been a few years now since I heard it first-hand, but it was either at Arlington or Langley when one of Van's engineers said that when the factory is building parts for assembly, deburring consists of running a scotchbrite pad across the holes to remove any burrs, but no work on individual holes. ie. on a flat skin, just wipe a scotchbrite along the hole line. He said there's no reason for a builder to do more.
 
az_gila said:
I agree - If you read the rivet spec., the only reason for deburring is to get the sheets to "sit" together with no gaps before riveting.

It specifically says that a stack of material does not have to be taken apart if it was tightly clamped when drilling.
Click to expand...

Another grenade...on the 12, Van's says punched holes do not need to be deburred as what you are feeling is a ridge created by the punch, not a burr. I haven't started building yet, but to those who are and are following this guidance, do the parts fit tight?
 
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I'm not yet through the whole document, and it is about flat rather than dimpled material. It compares cycles to failure of "production" and "polished" drilled holes.
 
nineninefour said:
I'm not yet through the whole document, and it is about flat rather than dimpled material. It compares cycles to failure of "production" and "polished" drilled holes.
Click to expand...

Sorry, hit the "Send" on my ipad app.

http://www.tc.faa.gov/its/worldpac/techrpt/ar0756v1.pdf

It sounds like we probably ream rather than just debur our holes, and less is possibly better. (The collective "we" since I'm not actually building yet, but based on the EAA Van's workshop and the discussions here...)

The goal of deburring should probably only to remove the burr and never chamfer/ease the edge of the drilled hole. The PDF has some interesting micrographs of burs formed in drilling. It also point out some drilling technique variables that may affect fatigue life.

But, the most interesting discussion is the mention of significant cracking in a couple of Boeing 707 wings (as an example of typical commercial aircraft.)
 
jlfernan said:
Another grenade...on the 12, Van's(and FAA AC 43.13-1B) says punched holes do not need to be deburred as what you are feeling is a ridge created by the punch, not a burr. I haven't started building yet, but to those who are and are following this guidance, do the parts fit tight?
Click to expand...

Where does it say that in AC43.13-1B?

All I can find is Section 4-58 covering Alum structure repair methods.

It specifically says...

Deburr the hole with an oversize drill or deburring tool.
 
az_gila said:
Where does it say that in AC43.13-1B?

All I can find is Section 4-58 covering Alum structure repair methods.

It specifically says...

Deburr the hole with an oversize drill or deburring tool.
Click to expand...

Gil you may be right. I thought I read that on here somewhere, I guess my ginkgo-biloba had worn off when I typed it. Thanks again for an education.
 
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