Introduction: Hotwire Foamcutting Table

Picture of Hotwire Foamcutting Table

Good for cutting pink foam and blue foam.
The hot wire goes from the c-clamp on the overhanging arm, straight down through a hole in the table to a screw on the underside.
My friends liked to cut yellow, brown, and other foam with it, but that's crazy.
Why breathe poison gas if you don't have to? The blue and pink fumes are bad enough.

Now I prefer to use an old carpenter's saw to shape foam, followed by sharp new sandpaper.
But some people just love the hotwire.

Step 1: Not Much to It

The cutting wire is a piece of tungsten unravelled from inside a toaster or a stainless strand unravelled from a yacht cable. A non-stainless steel wire such as from inside a tire works fine also, but doesn't last as long.
When protesters burn tires there's a lot of that stuff around.

The wire elongates a bit when it gets hot. The wooden leaf spring at the top keeps it tight. Nitinol wire shrinks when hot, so that's not a problem.

The electronics consist of connecting the cutting wire across the output of a 24 volt transformer taken from a dc powersupply. That transformer is plugged into a variac plugged into a footswitch plugged into an isolation transformer.

Some wires have higher resistance and get plugged directly into the variac.
That's why that second isolation transformer is there, to make it a little harder to electrocute yourself.

This table also has a skilsaw bolted to the underside to use it as a tablesaw for cutting wood and aluminum.

If none of this vocabulary is new to you, you can figure out the safey issues yourself.
Stay healthy and safe.


0087adam (author)2008-12-11

Can u add a lot more detail? i cant really get a grasp on it.

gypsynet (author)2006-09-03

Looks good for fine work but I have always used your typical electric kitchen knife to cut foam with a minumum of mess and no toxic emmisions.

eur (author)2006-07-01

If you use a 24V transformer and a variac, the isolation transformer isn't necessary. The 24V transformer will isolate your cutting ire from the mains. How many Watts does this cutter draw? 100?

radiorental (author)2006-06-29

here's a more detailed instructable on making a hot wire cutter

wwtraveller (author)radiorental2006-06-29

know it all

radiorental (author)wwtraveller2006-06-29

If I knew half the stuff Tim forgot on his little finger I'd have a penny for everything in both our collective toolboxes

About This Instructable




Bio: Tim Anderson is the author of the "Heirloom Technology" column in Make Magazine. He is co-founder of, manufacturers of "3D Printer" output ... More »
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