Picture of Hot Wire Foam Cutter
I recently decided to try to build an RC airplane and needed a clean and effective way of cutting the foam I will be using for the plane. After some research I decided that a hot wire foam cutter would be the best solution. 

I wanted something that would be able to produce clean, even, reproducible cuts so a hand help cutter was out of the question. I ended up going with a band-saw type of design.

Step 1: Tools & Materials

Picture of Tools & Materials
Materials Used:

>2x4- x2 18" pieces & x2 15" pieces
>1x2- x3 15" piece
>Sheet of some sort of flat surface- I used 1/16th ply board

>Drywall Screws- 1-1/4" & 2-1/2"
>Adjuster Bolts- 2" (top) & 4" (bottom) + nuts
>Metal Plate Roughly 4" square + 2-1/2" Bolts (optional)
>Wire tensioner spring + Washer (Of equal outer diameter)\
>Shaft (Of inner diameter equal to above OD)
>Some sort of bead (I used a fishing lure sinker)

>Thin Steel Wire
>Power Supply


Saw (Ideally mitre saw or circular saw)
Drill (with some drill bits)

CaseyCase2 years ago
1/16" ply board? Are you sure?
spizzak (author)  CaseyCase2 years ago
Yes, why?

It's a little thinner than ideal maybe but it's what I had around the house.
I'm sorry. I have never seen plywood thinner than 1/4"--I though it was a typo.
delonzo2 years ago
Make me one
MrGreggan2 years ago
Will this cut thru foam core boards? If so, what thickness cuts best?
spizzak (author)  MrGreggan2 years ago
It would depend on what the outer layer is. If it is something that could be cut with hot wire then yeah it should. I'm not sure about thickenss- that would depend on wire gauge, and PSU current.
Slicerr22 years ago
hi um would it be possible to use stainless steel wire
guitar strings are stainless steel, so yes
okieinAZ3 years ago
It's not a great idea to use galvanized wire (as shown in your photograph). Heating galvanized metal can release toxic fumes. Breathing them causes metal fume fever. Try to get some NiChrome wire (perfect for cutting foam). Maybe a guitar string, if that's easier to come by.
spizzak (author)  okieinAZ3 years ago
Thanks for the tip but I don't think this wire gets anywhere near hot enough to release the toxic zinc oxide.
Sorry, but "I don't think" doesn't trump okienAZ's valid info. I won't tell you what to do, but others making hot wire cutters should rather choose a different wire.
oldmicah3 years ago
Awesome! Been wondering how to do this for a while... Can you give a little more detail on the steel wire you used?

many thanks
spizzak (author)  oldmicah3 years ago
Added a picture of the wire I used.
Excellent! Now I have some work to do before Halloween season comes upon us. Thank you!