How to make a hot wire foam cutter

wirecutterI have been making scratch built riggers for several years. My sponsors employ the wood over foam design. It was not until recently that I decided to try to use a hot wire because I was hoping to make several of my new .12 size riggers and thought it might be worth the timesavings. It was the right choice. I know the idea of hot wire cutting foam might be a little intimidating…I was myself. I thought it would be expensive and hard to do…wrong! Its simple, inexpensive and a major time saver. Here is how to make your own!


Scrap wood free
Angle aluminum / iron $1.00
2 eye bolts $1.00
Nicrome wire (buy this at your
local hobby shop)
Wire (goes to your power
Misc. nuts bolts free
12 volt battery free / ???
Total Cost$ $4.00

How to build the cutter:

To cut foam with a hot wire you will need to make a bow to hold the wire and keep it tight. The wire expands when it gets hot so you will need to be able to adjust tension easily. Simply put cut a U out of some scrap wood (1/4 light ply is what I used). Mine has a 5-inch gap that is 4 inches deep. The sides of the U are 1 inch wide and the top is 2 inches. This will give you strength and the wider top will give you something to hold on to. You can adjust these dimensions to suit your needs. Then cut 2 pieces of some angle aluminum. Bolt the angle stock to the U with two nuts/bolts each.

This gives a mounting point for the eye bolts used to tighten the wire. I used wing nuts on the eyebolts so that it would be easy to adjust while the wire is hot. On each side, use one of the bolts to attach the wire that will go to your power source.

The power source does not have to be anything fancy. I tired my car battery but that was way to powerful and it would melt the foam so much that it would not be accurate. Next, I tried my small starting battery that was half-dead from the winter and it worked well. I have been told that model train power transformers work well also.

How to use it:

Step 1…makes sure the wife is out of the house! Melting foam raises a stink!

You will need to get the heat of the wire hot enough to cut well but not to hot that it just plain cooks the foam. The only way to do this is get some foam and try it out. It took me 1 messed up sponsor to get the hang of how to move the bow along the jig to make good cuts. It does take a bit of practice but do not worry it’s not bad. Make smooth long strokes and doesn’t stop or it will leave a mark/smudge.

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