Cutting 3.5" foam insulation board

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Any ideers?
JP
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On Friday, November 2, 2012 6:16:28 PM UTC-6, JayPique wrote:

I use a manual and electric knife for cutting various upholstery foams and use 781 dry silicone to help the knife glide through the foam easily. I don't know about foam insulation. Might try some 781 dry silicone to help the knife glide through the insulation. Should be available at your local upholstery supplier - http://www.perfectfit.com/24783/247264/Upholstery-Adhesives/VS-Dry-Silicone-Spray.html Just whisk a light coating onto the knife blade and cut away. Respray the blade periodically/after several cuttings.
Sonny
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snipped-for-privacy@aol.com says...

781 dry silicone to help the knife glide through the foam easily. I don't know about foam insulation. Might try some 781 dry silicone to help the knife glide through the insulation. Should be available at your local upholstery supplier - http://www.perfectfit.com/24783/247264/Upholstery-Adhesives/VS-Dry-Silicone-Spray.html Just whisk a light coating onto the knife blade and cut away. Respray the blade periodically/after several cuttings.
At home I just plop foam insulation down on the table saw and treat it like wood. Helps to have a big cyclone dust collector.
When I'm not at home a snap blade knife does fine--the kind that DoItBest sells for 3 bucks. <http://www.doitbest.com/Utility+and+craft+knives-Do+it+Best-model - 314196-doitbest-sku-314196.dib>
Never thought to try lubing the blade--next time I have foam to cut I may try some bowling alley wax on it.
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says...

A hot wire works great on ridgid insulation foam. You can do very detailed work. At that thickness, it may be slower than you like, though. DON'T use it on polyurethane foams - makes toxic fumes. Kerry
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On Sun, 4 Nov 2012 05:27:00 -0700, J. Clarke wrote

There is a free video on finehomebuilding.com where the guy swears by a wide putty knife. He shows it cutting 1" (or so) foam board, but it might apply to the thicker stuff
FWIW -BR
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Curious... I would think it would tear and grab. If you sharpened the edges, it might cut through nicely.
Puckdropper
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On 11/5/12 11:31 AM, Puckdropper wrote:

Depends on the "foam." Putty knives work great on some rigid without sharpening and not great on other stuff without sharpening. I'm still not convinced everyone in this thread is talking about rigid foam when offering their opinions.
--

-MIKE-

"Playing is not something I do at night, it's my function in life"
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For 1", use a nice little linoleum (or other hawkbilled) knife.
http://tinyurl.com/a8gck47 http://tinyurl.com/bfgu6vw Firefighter kerambit (in my truck) http://tinyurl.com/a2besvd rigging knife (in my backpack)
-- While we have the gift of life, it seems to me that only tragedy is to allow part of us to die - whether it is our spirit, our creativity, or our glorious uniqueness. -- Gilda Radner
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Paste wax works fine.
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A hot wire cutter or an electric carving knife. Art
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Hot wire works beautifully with a jig or template. Cuts equally well in all directions, IOW a mother to control freehanded. Smells like burning styrofoam, best done outside.
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As suggested, a hot wire or the multifunction tool with a straight scraper blade.Works like a charm.
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On Fri, 2 Nov 2012 17:16:27 -0700 (PDT), JayPique

Hot wire is best, bandsaw is good, electric knife works, handsaw works well.
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Depends on how big of mess you want to make. A serated knife will cut through foam effectively, but creates a bunch of static charged dust that gets all over the place.
A long thin (really thin) non-serated blade will make less mess, but at the expense of signifcantly increased drag as you try to cut through the material. A sharp and honed blade does help quite a bit.
A hot wire foam cutter would be the next best thing. If you make your own, you can do it for a fraction of the cost of the commercial ones. I used a model train set transformer and some replacement hot-wire tool wire (from the hobby shop) as the base of mine. The wire needs to be stretched between a couple of posts for straight cuts, but that's easy enough from a woodworking standpoint. If you're interested, I can point you to more detailed instructions.
For carving, a SurForm rasp does a great job at making a mess and a good job at carving.
Puckdropper
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I agree w/ Puckdropper. I have made my own hotwire cutter the same way. Also a kitchen knife works ok. I have a jig saw blade that is basially a razor blade. You can make your own by taking a carbon steel blade and using a belt sander to put a blade on. I would try the silicone spray, or teflon spray too on a kitchen knife or jig saw blade.. don't re-use the kitchen knife after that.
On 11/2/2012 11:17 PM, Puckdropper wrote:

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Score it with a razor knife then snap it.
Jerry
http://community.webtv.net/awoodbutcher/WOODPROJECTS
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On Fri, 2 Nov 2012 17:16:27 -0700 (PDT), JayPique

Depending on the type of foam and shapes you need: CNC router, angle grinder with flap disc, and/or hot wire cutter.
A handheld router, scroll saw, or coping saw work in a pinch, too.
If you're really dextrous, try a katana. Please film it if you do.
BTW, I love your question. It reminds me of people who would call the body shop on the phone and ask for an estimate for their collision damage with "It's a blue Chevy, I think." as the entire details. <sigh>
-- The great thing about getting older is that you don't lose all the other ages you've been. -- Madeleine L'Engle
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On 11/2/2012 7:16 PM, JayPique wrote:

circular saw, knife, etc all work.
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On 11/2/12 7:16 PM, JayPique wrote:

Rigid? Utility blade-- score and snap. Soft? I've never seen soft foam insulation board. :-)
--

-MIKE-

"Playing is not something I do at night, it's my function in life"
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Just to add to the list...
A hand saw would work well. The traditional Western-style saw will make short work of the foam, at the expense of staticy dust and rough edge. Since you'll get a rough edge anyway, it doesn't even matter if it's very sharp.
Puckdropper
--
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