Dimple and Deburr Sequence

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Alan_VA

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Apr 17, 2011
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Bristow, VA
New kid here. The purposes of deburring thin aluminum is to clear out the hanging chads and to eliminate stress crack starting points. For thin aluminum skins (0.020, 0.025) is the sequence drill, dimple, deburr or is it drill, deburr, dimple?

Thanks.
 

Victor Bravo

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I would guess deburr first, because dimpling stretches and stresses the metal. If there is a burr (or rough edge) present when the metal deforms (into the dimple) there would be a slightly greater chance of that burr causing uneven stress.
 

Alan_VA

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Apr 17, 2011
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Bristow, VA
N804RV - With ~6,000 holes to deburr, and 69 year old elbows,
I'm thinking of an electric screwdriver and the Cleaveland Aircraft Tools DB04 deburring bit. Does that make sense?

Alan
 

gtae07

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Dec 13, 2012
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Savannah, Georgia
That's how we did most of them on Dad's RV-6. I typically use either a 3/16 drill bit in my fingers, or a dogleg tool with a three flute cutter.

The important thing is to not over deburr, especially on thin sheet. All you need to do is take the burr off; you don't need a noticeable chamfer.
 

Angusnofangus

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Sep 29, 2015
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Victoria, Canada
The aircraft manufacturer that I worked for required in their production standards that holes be deburred only on the exit side and only with a file. What was commonly used was a small section of vixen file glued to a block of wood. Worked great and much faster that deburring each hole. This is to avoid chamfering the hole. If, by using a deburring tool of some sort you chamfer the hole .001 on each side of a .020 skin, you have reduced the cross section by 10% at the hole. 10% is generally the threshhold for acceptable damage to a skin. Best to avoid it.
 

TFF

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Apr 28, 2010
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Memphis, TN
I’m sure they are not building over polished Oshkosh want to be’s. As odd as it sounds most of the engineering jobs is to ok the scratches and anomalies in manufacturing. When my old regional airline got all new planes, I got to see the documents of a new airplane. The anomaly book was around 3000 pages on old tractor feed computer paper. Their lawyers have to protect from your lawyers.
 

rv7charlie

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Nov 17, 2014
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Jackson
The guys at Van's a/c advise their builders to use a scotchbrite *pad* on prepunched holes in 2024.

Of course, a manually drilled hole using a dull bit in 6061 will leave more of a burr. If you dedicate a narrow (sharp) wood chisel to deburring by rounding the corners, you can slice off burrs that are too big for scotchbrite.
 

Mad MAC

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Dec 9, 2004
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626
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Hamilton New Zealand
If I recall correctly holes are dimpled at pilot hole size and then drilled / reamed to final size, to ensure a good rivet fit.
 
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