Make your own hot-wire or styrofoam cutter

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On this page: Generalities - What you need - How to - Evolutions - Home made filicutter - Conclusion


Filicutter is a tool to hot cut styrofoam, which allows you to highlight any piece recovered, and do so a lot of things: modeling, layout, visual arts, etc ...

Filicutter principle 1

The principle is quite simple, there is a strong electric current in a thin resistive wire. The wire under the effect of current, heat and cut easily and cleanly styrofoam, much much better than with a knife or a cutter, particularly for large pieces (> 5 cm thick). It can also be use to cut plastic or synthetic foam.

Build a filicutter is only adding a current source to resistive electrical wire, adding a control switch and possibly a light bulb to limit a bit the current passing through the wires.

Filicutter principle 2

And of course mount the whole on a structure, insulated, easy to handle, so you can control the hot wire during phases of cut. The idea was to do something that looks like a bit to a saw wire, a kind of huge "U" who owns a handful at the end. Like this:

Filicutter principle 3

This way you control switching on/off heater wire with a finger, and guide cutting with the same hand.

What you need

  • Resistive wire: not easy to find, you can try electronic components dealers, hardware, paint stores or plastic arts shops. This wire (sometimes called "constantan"), can also be replaced by piano chord/wire but's it is more fragile. Other idea by Alain, the recovery of resistance in an old radiator or electric toaster, you may need to increase or decrease the energy voltage depending on what you want to obtain (see below)
  • A piece of plastic pipe: to do the handle, take about 10 cm or 4 inches of plastic plumbing pipe
  • A push-button: for switching on (electronic components dealers)
  • A piece of metalic pipe of 1 cm diameter: To make the "U", at your size. Mine is 26x30 cm or 10X12 inches, made from an old aluminium tent pole
  • Electric wire: To put electric power to heating wire throught push-button. Take any kind of wire, with two sub-wires, and not too thin (bigger than telephone or network wires)
  • A power source: One more time, anything you can get who could deliver a 20 volts power, no matter AC or DC (I use an old car battery chargeur)
  • Miscellanous: Electrical scotch-tape, some bolt and nuts

How to

When you've read the principle, you can do it in your way. Here is mine, made with resistive wire and car battery charger.

Fold metalic pipe to make the "U" according to your dimensions.
Cut the handle in plastic pipe. On top of this pipe, make (using a saw) a place for the "U". Make a hole for your push-button, in the right place for your finger as a trigger. Connect two wires to push-button, and put them inside the handle. filicutter
Put the "U" in the handle, let 2 cm - 1 inch exceed, and fix it by making two holes througt the handle. Put two bolts in those holes, and put two nuts on the other side. You should have in your hand something light, with push-boutton right under your index. filicutter
Add then the resistive wire on the "U". On top, use a small metallic bolt with a ring head. You shoud use metallic bolt because and electric contact is needed on that side. filicutter
On bottom, contrarily wire should be insulate from the "U": use a small piece of wood, fixed with another bolt and nut, then another metallic bolt with a ring head. filicutter
Then connect:
  1. One arrival of power to the "U" (using an alligator clip for example).
  2. The other power arrival on one probe of the push-buttonl
  3. The second probe of push-button to the bottom metallic bolt with a ring head

That's it, it's over, you can now discover the happiness of precision cutting styrofoam...

Alain told me that you should be careful with styrofoam smokes when cutting, they are toxic and should not be breath.


Filicutter with handle like this one is very useful for... sculpturing styrofoam, but it's a bit difficult to make straight cuts.

If you have this kind of cuts to do, it could be interesting to improve it by making a kind of stand. The idea is to make this stand with a right-angle system and another push-button commanded by your feet, so that your two hands are free to control the styrofoam piece move.

To do that, you should make a small table, with a hole in and where the wire pass through. Table and filicutter should be in right angle, stable and connected, for example in a clamp.


Home made filicutter

Here is some photos of mine (click to enlarge) :

filicutter filicutter filicutter filicutter

Grip detailTop nail detailFixing detail
filicutter filicutter filicutter filicutter
Connected to a car abatterry chargerWorking on claw-back styrofoam pieceSharpen curtCutting table...
filicutter filicutter filicutter filicutter a clamp.Filicutter in p.laceFeet action
filicutter filicutter filicutter filicutter
Also cut shapes...
filicutter filicutter
more complex.Also cut foam


You could now, according to your needs, enhance the filicutter. Just in case, here is some lines of enquiry:

  • Using a lamp to enlighten the place where wire cut (more comfortable).
  • Adding a guide for cutting on a side, to be sure to have straight cutted pieces.
  • Adding a regulation sytem for bending wire, no matter it is cold or hot.
  • Etc...

Of course, if you want to give or ask precisions or informations, don't hesitate to contact me.

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Last modified on: August 11th 2018

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Your 42 comments or questions on this page:

I want to make a hot wire cutter to cut round grooves [1/2"; 3/4"; 1"; etc. in the styrofoam portion of ICF [insulated concrete blocks] after installation for plumbing and electrical channels. How can I make a cutting edge in a U shape for this purpose? 26 gage nichrom wire is too flexable for the U.
By David october 1st 2010 at 21:48 (n° 1)
Maybe you can use the heating wires inside a reformed old hair-dryer?
By jh october 2nd 2010 at 16:50 (n° 2)
Will guitar string work?? Have tons of that.
By papastash november 21th 2011 at 08:08 (n° 3)
I don't know, probably yes, but it should be tried.
By jh november 21th 2011 at 11:51 (n° 4)
Good job on your wen page! Is the battery 6 Volt or 9 Volt?
By Maynard april 20th 2012 at 21:34 (n° 5)
it's a car battery, 12 volts.
By jh april 21th 2012 at 10:06 (n° 6)
How about household current? (e.g. plug into house outlet?)
By Bob june 28th 2012 at 14:26 (n° 7)
No, too high in volts and so too dangerous.
By jh june 28th 2012 at 15:03 (n° 8)
I have sheets of strofoam which is 30" X 20", and is 6 cms wide. What I need to do is to slice the sheet into 1 cm widths. Will I be able to do this, using your method?
By Joyce january 21th 2013 at 06:49 (n° 9)
Yes, but you need a cutting wire of at least 20 cm long.
By jh january 21th 2013 at 13:23 (n° 10)
cain i used 24dc 1.5amp rectifier,what size of wire element should i used
By Anonymous march 5th 2013 at 03:31 (n° 11)
Yes, make tests to find the right one.
By jh march 6th 2013 at 09:04 (n° 12)
i just wana run to get one it seems to complex
By Anonymous march 8th 2013 at 04:57 (n° 13)
Not so much...
By jh march 8th 2013 at 11:07 (n° 14)
Can i use adapters so that i can reduce the volts if i'll plug it in a house electric outlet?
By JC march 21th 2013 at 07:51 (n° 15)
Yes, no problem.
By jh march 21th 2013 at 09:11 (n° 16)
Thank you for this great tutorial. What is the thickness of the resistive wire that you used? Thanks.
By Jim february 19th 2014 at 01:22 (n° 17)
It's a 4/10 of mm thick
By jh february 19th 2014 at 13:31 (n° 18)
It sounds too good for me and be the fact that I have much interest in the subject matter. I still get lost with the way you are gaging the wires. Could u please use the (mm) just for me to understand
By CHRIS february 25th 2014 at 10:25 (n° 19)
Already indicated, but it's 0.4 mm.
Anyway no need to be precise, any wire will be ok.
By jh february 25th 2014 at 11:46 (n° 20)
we are trying to construct a hot wire cutter to split 4 inch thick foam board into 2 inch thick. It needs to have an approximate 4 ft. cutting wire area. Will we need to increase voltage or will a commercial battery charger work for this length cutting wire?
By TED february 26th 2014 at 19:52 (n° 21)
No, I don't think so.
But you'll certainly need to push the piece of foam a bit slower, to get a nice cut.
By jh february 27th 2014 at 08:50 (n° 22)
You can use the tungsten wire out of an electric bar fire with a 6v (square) battery for a more portable unit.
By ian september 21th 2015 at 16:37 (n° 23)
4volts battry can work?
It's just for science project.
By Sam december 19th 2015 at 10:22 (n° 24)
I'm afraid it's a bit low.
By jh december 19th 2015 at 10:28 (n° 25)
6 volts
By Sam december 19th 2015 at 10:34 (n° 26)
By jh december 19th 2015 at 14:48 (n° 27)
I have a microme 80 wire of 26 gauge .is it useful for make a hot wire fome cutter
By Anonymous february 4th 2016 at 16:49 (n° 28)
No idea what it is, anybody else?
By jh february 12th 2016 at 08:49 (n° 29)
you bet. goto:
By limpinlou march 30th 2016 at 18:54 (n° 30)
Would 18 volts be adequate?
By Ben july 23th 2016 at 01:16 (n° 31)
It depend on your wire size, but should be.
By jh july 24th 2016 at 03:02 (n° 32)
can I use guitar string on 9 volt power supply, I am combining my 5 4 volts phone charger
By simon september 27th 2016 at 17:39 (n° 33)
It depend of the size (diameter) of your wire, could be tried.
By jh september 29th 2016 at 08:56 (n° 34)
Science concept?
By jd november 30th 2017 at 15:13 (n° 35)
What is optimal temperature for cutting styrofoam and how to make ( for instance) 100W cutter if I have transformer of 17,5V?
By jure january 5th 2018 at 15:11 (n° 36)
I don't know, but it's a rather slow temperature, I mean the wire don't need to become red.
By jh january 6th 2018 at 06:22 (n° 37)
Dont go to Jacobs online. Service is terrible
By Jet april 22th 2018 at 23:36 (n° 38)
I like the page. I am desperately trying to make a hotwire cutter but getting kind of confused. Ive spent about a hundred dollars and gotten nowhere with what I thought was good information that I dug up on the internet. I like the idea of using a car battery. I need to be able to cut styrofoam about 4 feet in length.Is it possible with this kind of setup? What kind of wire will I need to hook up battery and what kind of wire for the cutting? Id appreciate your comment. Thank you.
By Jetjanitor may 1st 2018 at 20:59 (n° 39)
Yes it is, and everything about the cutting wire is in the text page.
For the battery wire use standard cooper wire of appropriate diameter (not too small).
By jh may 1st 2018 at 21:11 (n° 40)
Great tutorial, I've been entertaining making one of these or something similar to try and cut a memory foam pillow. With it being so dense do you think this method would work?
By Levi june 20th 2018 at 08:57 (n° 41)
Yes, I think so. I got friends who cut foam mattress for their baby bed with it.
By jh june 20th 2018 at 09:30 (n° 42)
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