What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

How to open up a panel hole from 2-1/8" to 2-1/4"?

lndwarrior

Well Known Member
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
 
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
 
Last edited:
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-Nibbling-Tool/productinfo/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
 
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.
 
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.
 
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)
 
Last edited:
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
RV-4 N82RB
 
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.
 
Good quality hole punch

It seems to me the only real practical solution is a hole punch. I just helped another owner with replacing a compass panel hole with a hole for a G5.

If you are working on a panel with instruments and radios installed, you really don't want the vibrations and aluminum chips and dust flying around from any file or dremel tools.

A hole punch gives a clean precise hole and you smooth the edges with 220 or 320 after the process.
 
Simple...use a 2 1/8 hole saw to cut 2 plugs out of MDF, screw/glue the two plugs together, slide plugs on your 2 1/4 hole saw and cut away.

Plugs act as pilot to center the 2 1/4 saw...
 
accurately mark the desired diameter with a fine sharpie, also tape if desired just outside of your diameter line. Use a die grinder with 3/8" dia cylindrical carbide burr and use the method described above by n82rb and creep up on the line. You can use the carbide burr or the sanding drum, I like the carbide burrs because they last a long time on AL and are fast. Then use a die grinder with the 1" dia scotchbrite drum to smooth and deburr. Using the carbide burr it will only take a couple minutes tops to enlarge your hole.

If the panel is in the plane and your'e doing the above secure your powerful shop vac nozzle right behind your hole if possible or in front and you will have very little mess from the filings. The filings from the carbide burrs are very fine. I have used two shop vac's in spots where I really don't want the filings.
 
Here is a technique that I have used when removing the panel wasn?t practical. You can get a 2? drum sander. Home Depot, Lowes or Amazon. Mark the hole as others have suggested and use the drum sander, moving it around the inside of the existing hole until you get to the desired diameter. I use a dial caliper to keep gaging the hole and can get a pretty round hole within .005? of the desired diameter. The grit size should be something like 60 to make quick progress. Maybe finer as you approach the finish hole size. Since the drum is nearly the same diameter as the desired hole it will be easy to keep it pretty round. Good luck.
 
Ditto on Dan's suggestion

Exactly what I would do, and have done many times. If your panel has access behind it, stuff some rags in there to catch dust,or tape a plastic cup behind it. and if you have an assistant, hold a shop vac to catch the grindings..should be a quick easy job.
 
Me too.

Yep, can't tell you how many times we have just taken a fine point Sharpie, made a rough cut 1/16th. off that and then filed it to the mark.
It what we do with soft metals. Your call, Yours, R.E.A. III # 80888
 
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.

I wish I knew about this method when I did the same things for my fuel tank skins. I ended up making a router template out of MDF and using a flush trim bit to cut the skin. It worked but required a lot more work to get everything set up. (I did practice this on scrap and would suggest you also do the same :) ) Lots of ways to get this done.
 
hopefully this was said already

You can put 2 hole saws on the bit / jig at one time. Put them both on which will use the smaller hole saw as a guide for the larger one.
 
Back
Top