How to make a 0.75" Hole in Stainless Firewall?

[DHeal]

I need to make a 0.75" hole in the "already installed" stainless steel firewall on my RV-12. What would be the best way to make this hole - drill bit, Uni-Bit, punch, etc? I prefer to not bleed. Thanks for any useful tips!

[Mike S]

I have had good luck with a Unibit.

So has this guy https://www.youtube.com/watch?v=ORXqvOevRbA

[BillL]

Drill Bit -NO - NO - NO
Unit-bit - OK
but make it one step undersize and then use a carbide burr or sand out to size. Be very careful - - don't touch it until sanded to final smooth.

If the undersize looks good, no distortion tearing etc. then go for the next one, otherwise use method above.

Best - punch! - still have to sand the burr

YMMV

[terrye]

I didn't have much luck with a unibit. Caught just as it was going through.
Much better luck with a rotacut sheet metal hole cutter. Back up the inside of the hole with a piece of plywood.
http://www.hougen.com/cutters/sheet-...e-cutters.html

[LifeofReiley]

Originally Posted by terrye

I didn't have much luck with a unibit. Caught just as it was going through.
Much better luck with a rotacut sheet metal hole cutter. Back up the inside of the hole with a piece of plywood.
http://www.hougen.com/cutters/sheet-...e-cutters.html

Yes... Yes... Yes and AMEN!

[Larry DeCamp]

The rota cut style will work. I used a high dollar carbide unit ( my brother in laws) and it was beautiful. If you only need one hole, try a cheap one.

[gasman]

Hi David, Just did one in my six..... Used a uni-bit, but started with a standard drill bit for the pilot hole. Center punch... drill 1/8"... then 1/4" then uni-bit. Used a battery drill motor on low speed-high torque and used a little cutting oil. Go slow and use firm pressure to keep it cutting. Did a nice job.

[spatsch]

Knock out punch works great just a bit expensive if you only need one hole....

[gasman]

Originally Posted by spatsch

Knock out punch works great just a bit expensive if you only need one hole....

The SS might be too thin to punch without adding a layer of scrap to the area.

[spatsch]

Originally Posted by gasman

The SS might be too thin to punch without adding a layer of scrap to the area.

I used the 1 inch punch from aircraft spruce:

http://www.aircraftspruce.com/catalo.../knockout2.php

As said worked great just needEd to debur the edges a bit when done.

Adding a layer of scrap sounds like a good idea just to be sure... .