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  #11  
Old 10-15-2012, 10:37 AM
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Ironflight Ironflight is offline
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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
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  #12  
Old 10-15-2012, 10:52 AM
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fl-mike fl-mike is offline
 
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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.
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  #13  
Old 10-15-2012, 11:05 AM
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az_gila az_gila is offline
 
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Quote:
Originally Posted by fl-mike View Post
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.
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.
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  #14  
Old 10-15-2012, 01:22 PM
rapid_ascent rapid_ascent is offline
 
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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.
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  #15  
Old 10-15-2012, 01:46 PM
Flying Scotsman Flying Scotsman is offline
 
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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...
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  #16  
Old 10-15-2012, 02:06 PM
localizer localizer is offline
 
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Quote:
Originally Posted by Ironflight View Post
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.
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.
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  #17  
Old 10-15-2012, 04:08 PM
g zero g zero is offline
 
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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 .
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  #18  
Old 10-15-2012, 04:52 PM
DaAV8R DaAV8R is offline
 
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Default 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.
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  #19  
Old 10-15-2012, 09:13 PM
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Snowflake Snowflake is online now
 
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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.
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  #20  
Old 10-15-2012, 09:55 PM
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jlfernan jlfernan is offline
 
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Quote:
Originally Posted by az_gila View Post
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.
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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Last edited by jlfernan : 10-16-2012 at 03:19 PM. Reason: Saw the error of my ways
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