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  #1  
Old 02-10-2019, 10:59 PM
Aero_Octaveus Aero_Octaveus is offline
 
Join Date: Aug 2014
Location: Edmonton, AB
Posts: 207
Default Edge Distance for Dimpled Holes

What edge distances are you using for 3/32" dimpled holes (AN426 Rivets)?

If I reference the MIL-R-47196A spec on Vans Website it shows Flush Rivets, Dimpled Holes as the "A" & "B" dimension (0.156").
https://www.vansaircraft.com/faq/mil...n-and-install/
However if you look at the original 1977 MIL-R-47196A spec it shows the same scenario as the "C" & "D" dimension (0.219")
http://everyspec.com/MIL-SPECS/MIL-S...R-47196A_2735/

Is this a discrepancy, or is the Edge margin reduced?
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  #2  
Old 02-10-2019, 11:15 PM
Bicyclops Bicyclops is offline
 
Join Date: Oct 2012
Location: LA, California
Posts: 229
Default Don't need to go to minimum edge distance

We teach 2D (diameter) edge distance to center of hole for AN470 and 2.5D for AN426 at the A&P school. That's figuring to countersink. Dimpling is stronger and I'd be plenty happy at 2D. They don't have to be at minimum edge distance, anyway. If you miss drill even a little, you can wind up below mins. An 1/8th" countersunk flush rivet calcs at 5/16" minimum which is right down the center of a 5/8" rib flange. A 3/32" flush rivet would fit in less than a 1/4", but why bother. Set them all at 5/16" edge distance and be done with it.

Ed Holyoke
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  #3  
Old 02-11-2019, 11:53 AM
Aero_Octaveus Aero_Octaveus is offline
 
Join Date: Aug 2014
Location: Edmonton, AB
Posts: 207
Default

2D and 2 1/2D is what the Standard aircraft handbook says as well, however it seems to be much more conservative than Vans rivet MIL spec, and the 1977 Mil spec.

Since my issue is a single solitary hole, and not a hole line of new holes I figure being less conservative is ok. If I reference the MIL spec on Van's FAQ page, then I am all good. However If I reference the original 1977 version then I have an edge distance issue.

I'm trying to figure out why the two MIL Specs are different, and which one is correct.



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Garet Hess - Edmonton, AB
RV-7A - Emp and Wings Done. Working on fuse
2018 Donation Current
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Last edited by Aero_Octaveus : 02-12-2019 at 09:03 AM.
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