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I don't like laser cut parts

lipper03

Builder RV14A & ZA750SD
Benefactor
Not liking laser cut parts, even with proper prep, including extra reaming, single flute deburr, and good dies, still getting some slight cracking that I have to file out.

Just needed to rant, but I did send support a message about this, because I think there are going to be a lot of cracks in the next few years.

These are after an hour of filing and pad work, start of cracks all on the same position. I should have taken shots with the original, after each prep step, but didn't.

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What part is that? Looks kind of thick for dimpling, typically you would countersink thicker parts ...
 
A light film of oil on both sides of the hole does wonders allowing the aluminum to form and stretch over the dies.
 
I find water jet parts much better. But still, if you are going to form the edges of a hole, for dimpling, or for the flare around a lightening hole, you need to file/sand the hole edges first or it will crack.
 
Laser cutting leaves a re-cast zone along the edges, which will be brittle. Recipe for fatigue in areas that are cyclically stressed.
 
Not liking laser cut parts, even with proper prep, including extra reaming, single flute deburr, and good dies, still getting some slight cracking that I have to file out.

snipped

View attachment 37845

Are those 4 large dimples for #8 screws? I had the same issue. Going from memory here, I believe Vans says to use a #19 drill bit. I was warned that this may cause cracking when dimpled. My RV guru [A&P, IA & built an RV4] told me to use a #17 bit instead. The slightly larger hole will not effect locating the screw, as the dimple will do that. It does prevent the cracks when forming the dimple.
 
These were #30 holes. I just think that the brittleness of the entrance/exit is an issue, and needs to be watched closely by builders and Vans over the next few years. This piece was the emp top skin doubler, and it's 0.0253 so well within dimple application thickness.
 
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Brian,
How thick is that material? Generally, you don't dimple 2024-T3 that is more than .040" thick.
 
My RV guru [A&P, IA & built an RV4] told me to use a #17 bit instead. The slightly larger hole will not effect locating the screw, as the dimple will do that. It does prevent the cracks when forming the dimple.

True, the dimple WILL center the screw, HOWEVER, the pilot on the die is what centers the dimple on the sheet to match the original hole. If you oversize the hole, you cannot still expect the pilot on the die to center the dimple to the exact hole. WIth a bunch of slop, the die will likely step over to one side of the hole and now the screw is forced to center in a location that is not consistent with the hole in the other piece. I would not follow that advise. Do this on a long row and are likely to get pillowing due to tolerance stack up.
 
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