Cutting Foam

[WTN4ICE]

A question for all you DIY guys or gals. I am looking for a way to cut a perfect 2 1/4 inch diameter circle in 1 inch thick foam. I tried a hole saw but did not get the clean cut I want. I also free handed some but also not the desired result. Any ideas or suggestions appreciated.

[NIBOWMAN]

Go to your local auto parts store and get a short piece of exhaust pipe with the desired ID. Sharpen the edge with a grinder and rotate and push the pipe through the insulation.

[WTN4ICE]

Had not thought of that...thanks.

[reddog]

what kind of foam and what density? EPS or XPS?

[WTN4ICE]

I have no idea just some grey foam from Macs.

[Jim Almquist]

Maybe go buy a cheap hole saw. It will be a perfect circle and should cost no more than $3.00.

[CAMAN]

Run the hole saw in REVERSE

[Eastwind]

Try rotating the hole saw backward

[hydro]

The sharpened metal tube is the way to go, and gives a cleaner cut than any saw. It will cut a perfect hole and be very smooth. An exhaust pipe, or even a tin can, cut and sharpened will slice right through the foam, with a light downward pressure and a twist.

I just used this technique a couple of weeks ago and it worked great!

[WTN4ICE]

Just tried a soup can...works great just a little big,need something 3/16 to 1/8 smaller. Will try a muffler shop for a scrap of tail pipe possibly from an import vehicle. Thanks Hydro for the tip.

[reddog]

If its grey, its more than likely XPS (Extruded Polystyrene). XPS cuts easier with the length of the sheet rather than across the sheet.

The problem with a hole saw, is that there is the foam wont hold the pilot bit in place. If the pilot bit moves, the hole saw moves.

A longer pilot bit that would go thru the foam and into a solid table or bench below would make a better cut.

Hole saw in a drill press would work.

[walleyehunter80]

what are you using these pieces of foam for?

[SkunkedAgain]

That's classified