Recommendations for making a 2" dia. hole in the firewall

[Dean Pichon]

After 8 years of flying, I've decided it's time to put heat in my -4. During the building phase, I found it very difficult to put even moderately sized holes in the firewall. What have other builders found to work to make nominal 2" diameter holes for heater plumbing?

Thanks!

[David-aviator]

Originally Posted by Dean Pichon

After 8 years of flying, I've decided it's time to put heat in my -4. During the building phase, I found it very difficult to put even moderately sized holes in the firewall. What have other builders found to work to make nominal 2" diameter holes for heater plumbing?

Thanks!

I was going to say a double barrel 12 ga might work...I used a metal cutting 2" hole cutter from Home Depot. Don't recall the brand but they are white and cost more than the red ones hanging next to them. It is a good idea to have someone hold a piece of 2x4 on the other side so as not to flex the firewall too much.

[Bushcaddy]

I did the same and it worked well. A word of caution if using something like a Greenlee slug buster. All the dies actually cut a bigger hole than what they are labelled for. A 2" cutter actually leaves a 23/8" hole. The home depot hole cutter did the job very nicely in about 5 seconds.

[jthocker]

I just used the biggest unibit I had, then enlarged the hole from 7/8's to 2 in. with a carbide burr in a die grinder. Finding someone to back up the firewall with the 2x4 has never been convenient for me, but may be less messy.

[allbee]

if you can get a hold of a hole punch for the panel 2 1/4, makes a real nice hole, easy to do. That's how I did my hole for the heat.

[647jc]

The heat box on my 9 is attached with a couple AN3 bolts on either side of the large 2" hole. I drilled the holes for them before drilling the larger 2" hole and then used a couple large wood screws and washers to fasten a piece of 2 by 4 behind the FW for backing. I then drilled the 2" hole with a typical metal hole saw, go very slow to avoid heat build up and use some type of lube.

[dhall_polo]

Kinda pricey, but this kit has come in very handy during the fwf and finishing stages. They work great.

http://www.drillspot.com/products/47...Hole_Punch_Set

[jsharkey]

Originally Posted by allbee

if you can get a hold of a hole punch for the panel 2 1/4, makes a real nice hole, easy to do. That's how I did my hole for the heat.

Same here - looks good and the flange on the valve is more than big enough to cover the extra 1/8" all around.

Jim Sharkey

[allbee]

Originally Posted by jsharkey

Same here - looks good and the flange on the valve is more than big enough to cover the extra 1/8" all around.

Jim Sharkey

Use it on the baffles also for the cold air.

[allbee]

Originally Posted by allbee

Use it on the baffles also for the cold air.

One more use for it was on the battery box.