For cutting thin foam, most of us would just use our benchtop water jet
machines.

An old sewing macine could possibly be adapted/modified to cut thin, soft
materials.

When I was making straps and various other accessories for boats that I had
years ago, I stopped in a local furniture upholstery shop to find out what
types of needles they used for thick, multiple layers of fabric, and the
friendly owner was happy to inform me of all sorts of interesting info
regarding thick materials (straps, parachute harnesses etc).
They use needles that cut as they pass thru thick materials, where common
single-pointed needles will get jammed in dense, thick materials.
I was able to gently grind the shanks of the commercial machine cutting
needles so they would fit an old Necchi home-type sewing machine, and the
cutting points made multiple layers of strap material and various fabrics a
breeze for the tiny Necchi motor.

I believe the cutting points were ground similar to an endmill, with the tip
ground as two bevels in opposing directions and with a greater relief angle,
which would likely require a good magnifier and possibly a mini abrasive
disk or stone in a rotary tool.

A cutting point that reciprocates rapidly could be very useful for cutting
fine lines in synthetic materials such as foam. While feeding the material
by hand (without using the sewing machine feed pawls, or thread), closely
spaced perforations/holes will essentially become a cut line.
The freehand feed mode is used for embroidery-type work with thread, such as
creating fabric patches with graphics on them (I watched this being done
years ago).

--
WB
..........


"Jon Anderson" wrote in message
...
Want to make a very simple hot wire cutter to cut polyurethane foam.
Probably not more than 12-16" span, max. Found a simple setup on
Instructables using a 24v 2a transformer and a wall light dimmer.
Well, I've got a 12v 4a DC power supply, seems to me that this ought to be
enough, but thought I'd ask.

Thanks,

Jon