On Tue, 01 Nov 2016 23:22:49 +0000 (GMT)
Stuart wrote:

I think it requires that the material be electrically conductive. I'm
surprised it works with graphite (not because of it's conductivity
but the nature of the material).

also what i thought

there is a part two of the video that i have not seen
the operator mentioned that 12mm deep is the critical point and that
is where part two starts i think

I saw a simple one demonstrated at a model engineering show and the
plans to build it were on a single sheet of A4 paper, I bought a set,
and it wasn't tightly drawn. A second much more elaborate one was
featured in "Model engineers workshop" (UK magazine) over two monthly
parts.

will have to look for that

I've seen nice, intricate, patterns cut into razor blades. Hardened
stainless steel and difficult to cut any other way because it's so
hard and thin.

what i have seen so far was all small scale

but i wonder if it is also used at large scale