cutting rigid foam insulation

[tuber]

I have a question about cutting rigid foam insulation. What aree the different ways to do it? Some of the cuts I have to make are not all vertical or straight lines. I'll be cuttting 1-1/2 thick foam.

[starleen2]

a good electric knife will do nicely or you could use a hacksaw blade - just be sure to tape up one end to use as a handle. You might want to have a vacuum handy to vacuum up any foam shavings

[alffink]

tuber

normally I'll just use one of the new box type cutters with the narrow blades, where you can just break-off the dull segment to give ya a new blade

straight cuts, I will grab a dry-wall square, relatively inexpensive, but very handy, gives a four foot straight edge with a three foot square

for those curved cuts, try one of the single handeled hacksaws, looks similar to a keyhole saw, which would probably work just fine also

Foam dosen't have to be perfect, but cut it so it will have a press fit into the void you will be filling, fill any large mis-fits with one of the areo-sol foams, that are used for around duplex boxes and such.

Foam cuts easy, but can be messy, that's reason my first choice is a knife.

[Zollinger]

For the Zollinger and now the Vagabond we use a carpet knife, the first pass about 1/2 way through, and the second pass to finish cutting through.

[Kevin A]

I also used an electric knife, worked like a charm.

[Miriam C.]

I used a cheap carpet knife for most of it. For the long kerfs I sent it flying through the table saw... pink stuff everywhere......

[cracker39]

I keep a couple old serrated edge steak knives in the workshop. These work well for cutting foam with very few loose particles from the cuts. I keep them sharp by laying the flat side against my grinder wheel or my bench disk sander for a few seconds. I have a couple of aluminum "yard sticks" (one is 48" long) as a straight edge.

After the foam is installed, if you have to cut grooves for wiring, here's the easy way with no mess. If you have a soldering gun that uses tips that have two ends that are inserted into the "barrel" of the gun and retained with set screws, find some solid wire (like a wire coat hanger) about the same diameter as the tip ends. Cut a piece about 3-4 inches long and bend it into a U shape, the bottom of the U being the width of the groove you need. Replace the soldering tip with this piece and use it to cut (melt) a groove in the surface of the foam the depth that you need. Where the wire has to cross a piece of framing lumber, I use a trim router to cut the groove in the wood.

[Tadlan]

Slow Cowboy is right. The hot wire is the way to go if you can get one for not too much. They are what foam sculpting pros use. I do not have one, so I use a bread nife.

[S. Heisley]

It takes patience, but this works, 'on the cheap':



You have to re-heat the knife for about 30 seconds after each 7 foot cut or after each full small piece is cut out, though.

[Miriam C.]

It takes patience, but this works, 'on the cheap':



You have to re-heat the knife for about 30 seconds after each 7 foot cut or after each full small piece is cut out, though.

Good idea!

[Lgboro]

I use a table saw for straight cuts and my jig saw for the other cuts.

[NathanL]

Homemade hot knife, took an electric soldering iron (the pistol grip kind) and cut length piece of coat hanger and made a loop out and back into the other deal.

Cuts like a hot knife thru butter and leaves a perfectly clean edge. Can also be used to follow a template as well. When you are done you take the loop of coat hanger wire out (use uncoated or clean it real well to get the laquer off the new kind) and put your soldering iron attachement back in.

Can use the cheapest $7 soldering iron from HF or wherever.

Similar to this, this one is made to cut a channel but you get the idea.

You can also make a loop and twist it in an "O" shape and cut a recessed channel/O shape deal under the surface to run wiring etc...with only the widge of the coat hanger wire cut at the surface etc...

[tuber]

It takes patience, but this works, 'on the cheap':



You have to re-heat the knife for about 30 seconds after each 7 foot cut or after each full small piece is cut out, though.

Great idea!!!

[tuber]

Homemade hot knife, took an electric soldering iron (the pistol grip kind) and cut length piece of coat hanger and made a loop out and back into the other deal.

This is another great idea. This is one of the things I like best about the forum.. Someone has already invented the wheel and they are willing to share!!!

[jss06]

I found using the backside of a bandsaw blade works well too. Very little mess and a nice clean cut.