Was going to ask if anyone knew of how to make one, but found this, which may be of use:

http://club.cycom.co.uk/hotwire/Hot_wire_cutter_for_polystyrene_foam.html

ATB

Simon

this has to be one of the most fun toys you can have. I have a reel of nichromium wire wire in the garage if you struggle to find some I'll post you a bit.

WATCH THE FUMES!

and don't get the wire to hot or it melts

Controllable transformers around 12V with 1 or 2 amp output work with thinner wire, I used to use a model railway transformer with an old coping saw framw with I think 5A fuse wire it gave a very fine cut with the transformer regulated to just below where the wire was red hot. run the power up from the botto or you could take out the transformer secondary use or cut out.

Caber

I had an old battery charger (nice big 15v 12A transformer). Added a dimmer switch on the transformer primary and pretty much job done. To be bling I put the secondary output through a rectifier which also allowed me to use the battery charger Amp meter to measure how much juice I was pulling. Cheap (I had the broken charger anyway) and works fine even with big frames. I use standard nichrome from Maplins. Now apparently the transformer needs a special dimmer because its inductive but I didn't use one and it hasn't gone pop yet!!!!

I used to do this when I was doing R/C model aircraft (great for making wings). I got my nichrome wire out of an old toaster, then hit a bumper crop when our clothes drier died. It must have had 200' of it in there! And I used a 12-V battery charger to power my cutter.... LOCOST!!!

Ditto re the wings.

i have even used an arc welder for the power..turned down of course.

You might like to see this:

http://newtier.vo.llnwd.net/o1/misc/graber/videos/HotWire.wmv

I did my entire car foam with that contraption. NiChrome wire works well. Use a spring tensioner to take up the slack caused by the expanding wire.