Cutting styrofoam

rickharmer(z4British Colum)May 3, 2006

Just so we're clear:I'm referring to Dow's Styrospan,in 1 inch panels.

Like others here,I've despaired of finding a clean way of cutting these panels.This afternoon,I spent time with my styro,shaping the form for a fountain.I have Exacto knives,bread knives,hot cutters and my power tools.Well,I found the most accurate,and least hassle,was using my variable speed jigsaw.Using a standard woodcutting blade,at a low setting,I was able to efficiently cut,with good accuracy,quie a few pieces,with little detritus.At higher speeds,it seems to throw off a lot of junk.Lower,it meant that I ended up with a coarse powder,easily cleaned up.Wore my mask to prevent inhaling any fun bits.I'll still use my hotknife(sucks batteries!),but the accuracy is not as good.

Maybe for my future septic covers...?

Just thought I'd pass it along.

Cheers from here

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Hi Rick,

what do you mean by "hot knife"?

I have an idea about rigging something up with nichrome wire; it would be nice to be able to easily cut and shape styrofoam,


    Bookmark   May 4, 2006 at 12:27AM
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rickharmer(z4British Colum)

The hotwire I got was about 10 bucks in a big costume shop in Seattle.Basically,2 "D" cells,a nichrome wire,and a switch.simple,works well,but sucks batteries pretty quick in the model i have.A fully tricked out"hotknife"(I misspoke my tool)that plugs in,was about 80 bucks,not in my budget.
I've used my hotwire a number of times.It's slower than my jigsaw,and you gotta have steady hands to use it!For rough shaping,odd little corners,the wire's fine.But,for long straight runs,Nope,i'll stick to my little buddy,the jigsaw.
Cheers from here and goodnight,Mrs.McGillacutty,wherever you are!

    Bookmark   May 4, 2006 at 1:11AM
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Thanks Rick. I've gone on a couple of styrofoam prowls in the past week or so; checking back-alleys. I did find some pieces that had some shapes that I'd be interested in, but they will need some cutting. Possibly gluing as well. Glorious weather, eh?



    Bookmark   May 4, 2006 at 10:10AM
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I wouldn't recommend cutting styrofoam with a hot knife.
The fumes of heated styrofoam are extremely toxic.
Here's a link..... scroll down to "S" for styrofoam...

Here is a link that might be useful: Heated Styrofoam Toxicity

    Bookmark   May 4, 2006 at 10:45AM
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Hey Rick --- I use an old yard-sale electric carving knife that works like gangbusters. The kind that has two serated blades that reciprocate against each other and the motor in the handle. Got mine for two-bucks. Stole the idea from an old buddy who was a prop-maker. Clean & fast with dang-near zero dust & "crumblies". Cuts material up to about a foot thick (it has a long blade). And it works on all kinds of other stuff as well.


    Bookmark   May 4, 2006 at 11:29AM
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Never thought of that... duh....I've got an electric knife I've had sitting in the drawer for years, that I never use. Thanks Tango!

    Bookmark   May 4, 2006 at 12:02PM
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Electric knife, eh? Who'd'a thunk. Well, it's good to see that someone has come up with a use for those things.

And, yep, looks like inhaling styrofoam is contra-indicated,



    Bookmark   May 4, 2006 at 2:36PM
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rickharmer(z4British Colum)

Like most plastics,caution is the order of the day.Hot knives have been used for some time,and one would assume in a well ventilated area.Craft services use it for prop building,artists use it to lighten projects(See Marion Lea Jamieson;article in the local paper talks about"..she builds an armature of styrofoam,carving it with a hot wire.."),some contractors use a hotknife to cut foamboard for insulation.
It ain't perfect and care MUST be taken with this stuff.Same applies when you cut it,unless it's absolutely dust-free.I wear a simple surgical mask while cutting;with my eyesight,I get REAL close to the foam,to ensure a good cut.
Tango-you asked about styro glue a while back.To confirm,I'm using LePage's Bulldog grip PL200.It's made for the job.Our contractor used it while building our house,and I'll take that as a recommendation.Comes in tubes(needs a caulking gun to use)or in a tin,using a putty knife.I'm using the gun right now,then smoothe out with said putty knife.Sets up fairly quickly,I wait until the next day to continue working on the project.
cheers from here
P.S.-the styrene in stryofoam is also present in cigarette smoke !!

    Bookmark   May 4, 2006 at 3:18PM
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Belgianpup(Wa/Zone 7b)

A long-bladed serrated knife works quite well on styrofoam --- the kind with the bevel on both sides is best.

Tip on the $10 D-cell hot-wire: Rotate your batteries. The unit sucks up the power quite fast -- remove the batteries & replace with another pair. Save the first ones and put them back in later, & they'll continue to work. I keep rotating 3 pairs at a time. It's not ideal, they do wear out, but that first blast of power isn't ALL their power, just let it stabilize (for lack of a better word).


    Bookmark   May 4, 2006 at 11:57PM
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I went ahead with what I had on hand, a nice knife that I use for slicing a roast, and carpenters glue. The knife works better than I'd expected; at least on this thickness of styrofoam; I'll shave it down to suit when it's dry.

(had to turn off the flash)

    Bookmark   May 5, 2006 at 1:23AM
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rickharmer(z4British Colum)

morning,Straw Dog.Is that a coffin you're making?Are we that bad?
Looks like you were using a fairly thick white foam.What was its thickness?Did you carve it down from a larger piece?Good job of cutting,too.You're very much an"on hand"type,aren't ya?Won't your sis give you heck for using one of her good knives for this?
Cheers from canada's West Coast

    Bookmark   May 5, 2006 at 11:33AM
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Hi Rick,
A coffin? Better lay off those Dracula movies for a while. On the other hand, maybe you're onto something. Egyptian sarcophagus reproductions.

re. the styrofoam here's a pic. The other side of the piece is a mirror of the highlighted side. Works out ok because the outer edges present two nice square faces for the glue.


    Bookmark   May 5, 2006 at 12:44PM
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billie_ann(6b PA)

If people knew what we use to make, saw, sift, glue, mold; they might be afraid to eat at our homes.
I use a blade for cutting polymer clay for cutting and shaping insulation board.
Strawdog, I have no luck using that white polystyrene. For me it crumbles and sticks to my work piece. The insulation board is a dense smooth poly that I can get more than one use out of. Billie

    Bookmark   May 5, 2006 at 10:13PM
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daybees(B.C. canada)

Straw dog
Please tell us about that cool background is it a painting??
I love it!!

    Bookmark   May 6, 2006 at 12:05AM
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Billie; covering this styrofoam, the way that I want to, should be ok. It does get around though; I just fished a couple of white specks from the top of a tomato I was frying. I'll have to check out that insulation board. Just did another styrofoam harvesting detour on my way home; through a light industrial area. Got a couple of pieces; not really what I was hoping for, but on the other hand, I'll be obliged to cook up something different. All with the tips and info that I'm finding on this forum. I guess that it's my turn to say, "wow! I can't believe that amount of good information shared in these posts. This forum is a gold mine. As well as the inspiration from the work displayed and linked to. A tip of the hat to all you fine folks".

Hi Debbie. You like the painting? Me too. It seemed like a good choice for a backdrop. It's the work of a fellow by the name of Grant Head.

    Bookmark   May 6, 2006 at 1:40PM
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Hi, has anyone ever used styrofoam for their Christmas Village? I'm getting ready to redo my mountains. If anyone has any cool pictures I would love to get some more ideas before I start cutting...


    Bookmark   November 10, 2006 at 12:13PM
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nmgirl(8 S.NM)

Electric carving knives not only work well on styrofoam they cut foam rubber like a dream!
Just a little tip from a former props maker.

    Bookmark   November 12, 2006 at 11:52AM
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I could use some help with a schematic on how to make a hot wire table cutter. I used a piece of counter top as my table, drilled a sufficient sized hole for the wire to pass through and purchased a door bell transformer that is the 10 watt type. Next I purchased a grounded three wire pig tail, a light switch and box. I used a piece of flat steel about 1" x 1/16" to make the bow. I bent the steel into shape and attached it to the table with screws and nuts. The transformer has 3 wires coming out of one end that are green, black, and white. I attached those colored wires to the same color wires from the pigtail and then attached the two green wires to the green screw on the light switch. The black and white wires I attached to the other screws on the light switch. On the other side of the transformer, there are two screws to which I attached one wire to the bottom of the table at the bottom of the cutting wire. The other wire I attached to one of the screws that mount the steel bow to the table. However, when I plug the power cord in and turn the light switch on, it blows the 15 amp circuit breaker. Don't know what I'm doing wrong.

    Bookmark   April 6, 2007 at 10:06PM
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rockhewer(z4 WI)

Sounds like you have a dangerous wiring problem on your hands. First off you to make a switch work you only interrupt one leg of the 3 wires (legs). Usually it's the black wire. So put the black wires on the switch.

The way its usually set up is, if you are using newer components:
Green is the Ground wire. Goes to the ROUND part of the plug.
White is the NEUTRAL wire. Goes to the LARGE spade of the plug.
Black is the HOT wire. Goes to the SMALL spade on plug.

This is a good example if you don't know what you're doing with electricity, have it done by someone who knows. I don't mean to jump on you too hard but you're lucky you've only tripped a circuit breaker. Breakers also wear out. Trip them too often and they may not work properly in the future and cause you a real problem.

Please be careful doing your own wiring. Find out FIRST how to do something.

Good luck.

    Bookmark   April 8, 2007 at 5:43AM
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standard rules say green is ground, white is neutral, and black is hot.
You wired a direct short when you wired the black to the white on the switch leg.
The green to the green screw is good, thats your ground. a ground does absolutely nothing...unless a short happens and then that ground saves your life.
Break the circut on the black wire only.
One black on the bottom tap of the switch and the other black that goes to the "knife" on the top tap. Wire the two whites together in a wire nut.
It would be so much easier to tell you what you did wrong if I could see it but from reading your description I think I got it figured out.
Id tell you not to play with stuff you dont understand, but it looks like rockhewer did a pretty good job of that already.
People are not worried about it because its just 110, more people get killed or seriously hurt by 110 than by high voltage simply because of the attitude that its a low voltage and OK to make mistakes so more people that dont know what they are doing play with it.
Electricity is pretty easy in a home. straight forward, nothing over 220 and nothing too complicated. It gets so many people in trouble. You really doneed a pretty good understanding of basic electric if your doing more than replacing an existing light fixture where you can just hook black to black and white to white and tap the ground on that green screw.
Get into 3 way switches and it will really screw up someone who doesnt understand it all.

    Bookmark   April 10, 2007 at 2:46PM
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