The Stovebolt Site Forums The Shop Area The Tool Chest Ridged Foam Cutting, the easy way

You may never have a need to cut any ridged foam
for your Stovebolt, unless you're going to use it in
the roof, doors or behind the seat. But if you're
getting your shop ready for winter and need to cut
some to shape you will probably run into the problem
of cutting it cleanly.
Of course the absolute best way has always been with a
hot wire but most of us don't want to go to the
trouble of making a hot wire saw so we are left with
using a saw or razor. The saw and it's dust makes a
real mess and most razors are way to small for an
inch or two of ridged foam and most of the time you
end up with the foam balling up in front of the razor
bladed.

Somewhere along the way I decided to try a BIGGER razor
and having an extra 4" Red Devil putty knife laying
around, tried sharpening the edge. I have an 8" Nylon
mesh deburring wheel mounted on one of my stationary
grinders that was ideal for lapping in a razor sharp
edge. I sprayed the blade with some dry lube
http://www.blastergroup.com.au/dry-teflon-lube.html
and low and behold, a couple of swipes and I had the
cleanest cut I'd ever seen on ridged foam. And it
stayed sharp thru the entire 4'x 8' sheet of 1" cut
in 6" wide sections.
http://www.pbase.com/dennygraham/image/152778351
http://www.pbase.com/dennygraham/image/152778350

Denny Graham
Sandwich, IL

you just like re-inventing wheels Denny a cheap Olfa knife with snap-off blades does fine for rigid foam, extend the blade far enough to cut the depth/thickness needed - what most construction folks around here use, and worked fine doing daBus floor with very little mess, does nice curves and notches too

Bill

Thought I'd just throw this idea out to help someone,
dint think I'd have to spend the day defending
my idea.

If no one tried to re-invent the wheel Bill, we'd still be
rolling our carts around on a slab of round tree trunk.
We used a lot of ridged foam at the lab for the cryogenics. Used
to make temporary dewers for LN2 and such. As I said, we would
cut it with hot saws or a saw blade.
This putty knife cuts shallow or deep, could cut thru a 1/8" to
4" thick piece, absolutely clean. It's ridged so it cuts as
straight a line as you would ever want. It's cheap, everyone
has a putty knife in their tool box.
But....maybe you guys up dar know some secrets that we
aren't privy to down here.
Taint seen any Olfa, but down here we do got
Fiskars rotary cutters:
http://www.pbase.com/dennygraham/image/152781177
Not deep enough for 1" and crushes edge.

Snap-Off utility blades:
http://www.pbase.com/dennygraham/image/152781178
Went dull quick, not ridged, probably wouldn't be
any good on 2" thick material and tears foam along
the cut unless it's held at a steep angle.

Cheap rotary cutter, same as Fiskars, not deep
enough crushes edge:
http://www.pbase.com/dennygraham/image/152781179

Saw, straight, deep and fast but the mess is obvious:
http://www.pbase.com/dennygraham/image/152781180


Denny Graham
Sandwich, IL

An electric kitchen works also......
Dan

"Re-invent the wheel" means there is already a wheel. Like already a knife that works. Bill was just kidding you anyway. and providing a alternate cutter for those who don't want to mess up a good putty knife. Both ideas are worth mentioning and any other ideas some folks may have. If construction guys use it, it is the best tool for the job. Can't see blades getting dull too fast cutting foam? Olfa sold "down here" by Home Depot, Sears, Grainger, Amazon, Ebay.....

not attacking Denny, so no need for defense, just pointing out there's inexpensive tools available to do the job this is the cutter I use, actually a freebie from a local tool store, but the same as the original Olfas and quite rigid enough - cuts the 2" foam board [without any ridges] just fine with the right technique, always take at least 2 passes per cut, first one shallow - I like using a straight edge and happen to have an 8' x 2" piece of 1/4" steel a carpet layer gave me that works a treat for long cuts on any material - an electric kitchen knife as Dan suggests would do OK too, but because they're usually serrated or wavy edged, more chips

Bill

ALL seem to be good idea's depending on the situation. I'd surely sharpen up a wide puddy knife before I'd drive 15 miles one way to get something else! You guys quack me up! I'm gonna name you "yeng and yang" or peat and repeat!

Gosh, I just love it when new idea's pop up.

Yes all great ideas for sure. A few of you do remind me of Yin and Yang. Geez, My Home Depot is only 1.5 miles. A lot of these ideas are on the internet.
http://www.finehomebuilding.com/how-to/video/cutting-rigid-insulation.aspx
Watch the video from 2008.

Dagnabbit, every time I come up with an idea someone
beats me to it. That's exactly what I was doing Bart
and that's exactly the way it worked for me. Other
than the way I sharpened mine and using a dry lube
it's the same idea. My blade wasn't a clean new one
and it had a tendency to stick and the PB dry lube
solved that.
Thanks for finding that video, it shows how well it
works much better than my still photos do.
If ya got foam to cut and taint tried it, I think you
will be surprised at how much better it works than
the utility knives.

DG

Shows you have a good inventive mind. Many here will use that idea I'm sure.

The electric kitchen knife is very nice for this.

Also does a bang up job on R-19, no frizzies floating around:
http://www.pbase.com/dennygraham/image/152873759

Denny G

I ground the teeth off a worn-out 16" long power hacksaw blade, put a razor edge on the first 4" of it, and it's used for cutting Styrofoam, etc. just like Denny's putty knife. 10 years of use so far, and I think I've stoned the edge twice.
Jerry

May try that with the insulation, got some to do and last time it was messy with razor knife.

Let us know how it works out for you John. I'll never
use anything else to cut insulation, no matter what
form it comes in.

Denny G

I think the key to the success of your modified putty knife is the curve in the cutting edge which provides for a better slicing action compared to a strait blade. Also the large handle and the overall shape of the putty knife allows you to manipulate it until you reach the sweet spot angle for efficient cutting. And don't fret not getting credit for not getting credit for inventing it. My father-in-law came up with the idea for the cardboard grease gun refill tube as a child, submitted his idea to a magazine that was asking for tips and new ideas. Low and behold, a short time later there was cardboard grease tubes everywhere. I invented the two wheeled wheelbarrow on the floor of a hardware store many years ago. Still waiting for the royalty checks that ain't coming.

https://www.stovebolt.com/ubbthreads/images/markup_panel/default/bigger.gif
BUT A THIN SKIN

And a short memory, did I step on our toe Gary???
If I did, sorry buddy.

Denny G

No problem, just running my mouth. My skin is very thick.

Making a perfect clean edge of any desired angle on rigid insulation board is accomplished by using a table saw with a combination blade. Intuitively one would think it would melt the foam, but it doesn't. Try it you'll like it.

A little saw dust in your shop Paul??????

DG

It creates no more dust than when cutting wood. You've got to break a few eggs to make an omelette.

Paul, this thread was started because Denny invented a way to make omelettes without eggs

Bill