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  #1  
Old 11-12-2018, 10:47 PM
lndwarrior lndwarrior is offline
 
Join Date: Mar 2015
Location: Cloverdale CA
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Default How to open up a panel hole from 2-1/8" to 2-1/4"?

I have three original instruments in my panel that have the 2-1/8" hole. I am considering replacing two of these with instruments that are only available in 2-1/4" hole.

So how do I cut the extra 1/8" out of the existing installed panel?

I'm guessing there is a simple answer to this but I can't figure it out. Obviously the cuts have to be precise.

I'm not crazy about trying to grind it out but maybe that's the only answer?Tape around the hole, draw the enlarged circle and go to town with a grinding stone on the dremel? Also try and cover everything from the flying debris!

Hoping there's a better idea,

TIA
Gary
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  #2  
Old 11-12-2018, 11:40 PM
lr172 lr172 is online now
 
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I did all my holes with a fly cutter style hole cutter. Hoewever, they are somewhat uwieldy and wouldn't want to use them free hand. They would require a brace of some sort to hold the pilot.

I would probably make the circle and do the tedious grinding and filling. They also make two piece punches that would work, but I think they are well north of $100 each. If you have a lathe, you could pretty easily make one. Don't think it would need to be hardened for aluminum work.

Larry
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Last edited by lr172 : 11-12-2018 at 11:43 PM.
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  #3  
Old 11-13-2018, 12:54 AM
YvesCH YvesCH is online now
 
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Hi, as mentioned before you could use a punch:
https://www.aircraftspruce.com/catal...clickkey=48434

Maybe ask at a Avionics Shop around you if you could rent or borrow one?
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  #4  
Old 11-13-2018, 01:23 AM
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Ed_Wischmeyer Ed_Wischmeyer is offline
 
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Location: Savannah, GA
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Lotsa options...
* A punch is a possibility but try it on scrap first;
* A dremel is a possibility. Maybe you could make a circular template and use that like a router guide. My guess is that you'd want a cutter, not a grinding stone/sandpaper;
* Another possibility is a pneumatic die grinder with a rotary file (more power!), but you might not want to attempt that with instruments still in the panel -- the vibration might be damaging to those other instruments, I don't know;
* The rotary file would be easier to use on the bench than in the airplane, probably true of all the options;
* You could also get a nibbler and use that to enlarge the holes. This one (http://www.cleavelandtool.com/Adel-N...uctinfo/NTA25/) is probably stout enough. After you nibble, file/grind it all smooth;
* And the last option is to make a false panel with the correct size holes, not worry about how well you open up the existing holes, and attach the false panel to the real panel. If the existing holes don't have mounting screws in the way, this might be an easy way. It would be ugly, but probably your easiest option for nice round holes if the punch doesn't work.

Sounds like way too much fun... :-(

Ed
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  #5  
Old 11-13-2018, 05:25 AM
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Jesse Jesse is offline
 
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I would try one of those hook debuting tools to start with. You only need to remove 1/16 of material around the whole perimeter, so that just might work.
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  #6  
Old 11-13-2018, 06:08 AM
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DanH DanH is offline
 
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If you really, really want clean edges, remove the panel to the drill press. Fasten a backup sheet to it (clecos or screws) with the necessary pilot hole for a fly cutter in the center of the existing instrument hole.
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  #7  
Old 11-13-2018, 06:11 AM
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maniago maniago is offline
 
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Draw your circle, nibbler to take out as much excess if you can use it, then get busy with the file. Talking about it takes more time than doing it......and any other method but the file will take more time in set up and is high risk with the little you have to actually take out. Patience is the word here.

(FWIW - I've done all my panel holes with a combination of enlarging drills, nibbler and old school file.....it works)
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Last edited by maniago : 11-13-2018 at 06:16 AM.
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  #8  
Old 11-13-2018, 06:17 AM
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n82rb n82rb is offline
 
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put tape around the hole with the proper sized marked. use a die grinder with a 1-1/2 inch drum in it. use a very light touch and work the grinder in a circular motion around the hole. the finer the grit on the drum the less material it takes off i would use a fine grit. try it on a bit of scrap, with a little practice you will get an almost perfect circle. ive found that a light pressure and a fast speed around the hole takes of a very uniform amount each pass.

bob burns
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  #9  
Old 11-13-2018, 06:26 AM
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parabuzzle parabuzzle is offline
 
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This is also an option if you want to go the holesaw route:

https://www.youtube.com/watch?v=9-pBlZa1RBI

Basically it would be the 2-1/8" holesaw nested in the 2-1/4" one so the smaller one is the guide for the bigger one.
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  #10  
Old 11-13-2018, 06:34 AM
bobnoffs bobnoffs is offline
 
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i've run into this with my builds a lot and in the end i tell myself''quit dinking around and use the rat tale files and be done''. in the end the file will be the quickest . with any power tool you are at big risk to make a mark somewhere and be sorry you went that route. even when i use a dremel[ the least likely to make you sorry] i finish the edge with the files.you can file that hole in 20-30 minutes with little risk.
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