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Old 05-23-2022, 06:22 AM
JeremyL JeremyL is offline
Join Date: Aug 2020
Location: Maurertown,Virginia
Posts: 197
Default Cutting the 6” hole, question?

So I’m a couple weeks out from having to make the 6” hole cut in the fuel tank rib. I have heard all the stories of using the fly cutter and how it can murder you if not careful. So my question is, is there any reason a 6” hole “saw” “cutter” cannot be used in place of the fly cutter? It is thin aluminum, so I’m just curious if anyone has tried it or has experience. Oh and yes before anyone says it, I know if you take your time and secure the piece to the drill press and use a slow RPM, the fly cutter will work well. Thanks guys. I tried to post a web link for reference of a possible candidate.

RV7A(in construction)
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Old 05-23-2022, 07:31 AM
flipmike flipmike is offline
Join Date: Aug 2019
Location: St. Paul, MN
Posts: 12
Default Well, 4-inch hole cutter was no problem...

Needed a 4 inch hole in a .032 thick skin. While I'd used a hand drill and did
3 inch holes successfully before, the larger 4 inch hole scared me. So I finally got around to buying a used drill press off Craigslist, and one of those HF hole saws. Great results.

This will show if your drill press table is precisely aligned, but even then no problem. I used 420 rpm setting as I recall, AND for sure use a cutting oil. I see no reason 6 inch hole saw would not work, but have not personally done that one.
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Old 05-23-2022, 07:54 AM
HFS HFS is offline
Join Date: Aug 2009
Location: Lemoore, CA
Posts: 483
Default Sandwich

Sorry about the quality of this pic - it was taken with a Polaroid (remember them?) in 1986 - but it shows the basic idea of "sandwiching" the rib web between two pieces of plywood to help eliminate the possibility of "hooking" an exposed edge when cutting.

This is nothing new, but I just thought I'd bring to your attention.

YMMV - and probably will.


Sorry about the orientation - the pic shows vertical in my documents file?
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Old 05-23-2022, 08:01 AM
edclee edclee is offline
Join Date: Aug 2008
Location: Lancaster, SC
Posts: 277
Default hole saw

I drilled three 6" access holes in the rear baffle of my port tank with a hand drill and a 6" hole saw without drama. All worked fine. Just take your time and don't use a lot of force.
Sonex/Corvair 2016 Finished, Sold 2020
RV-9A 2005 Purchased
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Old 05-23-2022, 08:11 AM
krhea krhea is offline
Join Date: Nov 2011
Location: Peck, Kansas
Posts: 192

Use a “duct hole cutter”, find an hvac sheetmetal installer and borrow his or let him cut your hole for you.
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Old 05-23-2022, 08:12 AM
Bavafa Bavafa is online now
Join Date: Oct 2007
Location: Sacramento, CA
Posts: 3,940

I have cut holes using a hole saw in a drill running in reverse direction. It take a bit longer time but it cuts clean and without issues.
N825SM RV7A - IO360M1B - SOLD
N825MS RV14A - IO390 - SOLD
N258SM RV14A - IO390EXP119 - Out of Paint shop & flying
Dues paid
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Old 05-23-2022, 09:02 AM
nohoflyer nohoflyer is offline
Join Date: Sep 2018
Location: Brooklyn, NY
Posts: 277

I used the fly cutter in a drill press I bought. It did the trick. Just take your time it might not cut all the way through immediately. And clamp the rib down tightly.
RV-7A builder
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Old 05-23-2022, 09:08 AM
Swoda Swoda is offline
Join Date: Nov 2016
Location: McAlpin, FL
Posts: 47

I used a harbor freight hole saw, the trick is to sand the entire outer edge of the hole saw smooth. It then cuts a very clean hole even with a hand held drill.
Ron Greene
CWO4, U.S. Navy, Retired
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Old 05-23-2022, 09:19 AM
David Paule David Paule is offline
Join Date: Dec 2009
Location: Boulder, CO
Posts: 5,358

I used a Malco HC1, which worked nicely. A bit of a rough edge but plenty safe. It's essentially a guided router that attaches to a drill motor. Hint, drill the center hole and put a center post (cut-down bolt) through the part into a piece or wood. Clamp the part and wood down and have at it. After, finish with a sanding drum.

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Old 05-23-2022, 11:10 AM
rmarshall234 rmarshall234 is offline
Join Date: Jun 2008
Location: San Diego, CA
Posts: 376

Originally Posted by Swoda View Post
the trick is to sand the entire outer edge of the hole saw smooth. It then cuts a very clean hole even with a hand held drill.

I did a one year stint as a helicopter mechanic and in that time I did 3 air conditioning installations on brand new Eurocopter AS350s. What is that about a 2-3 million dollar ship? of the first steps was to take an electric drill and chuck-up a 6 inch hole saw and drill a big hole in the tail boom. Talk about stress. However, everything worked out fine and this was before I knew about the above-mentioned trick. Yes, take a grinder and sander and remove the portion of the teeth that stick outward from center. There was tech article in one of the flying mags awhile ago about doing this.

Good luck and start on a practice piece.
Robert Marshall
RV-3 N333LT - 500hrs PIC
AFF Skydiving Instructor (Ret)
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