Not sure things can't be done other ways but years ago one of my manu.
engineers cut a magnet with it into some unusual shape I wanted at the
time. So operations on magnets are gentle so as not to cause
demagnetization.

Slow but smooth!

Paul

Pipper wrote:
"John Albers" wrote in message
m...

I am thinking about building an EDM (electric discharge machine) which
remove tiny bits of metal by sparks. I have found plans and
schematics on the web and in various magazines like Home Machinsts
Workshop. I could just blindly copy their designs, but I wanted to
understand how they work first. Most are build around a relaxation
oscillator circuit which charges a capacitor and the capacitor
discarges across a spark gap. Most of the EDM machines that I have
plans for work with voltages around 80-100 volts. Expreimenting helps
me understand things better, so I tried the following experiment:

I took a couple of old HP deskjet 40V DC wall warts and wired them in
series to produce 80V DC. I checked this with a DVOM and I am getting
80V DC output. According to various sources the break down voltage of
air is around 20V per .001 inch. I have a block of wood (pine) with a
notch in it holding two machine screws facing each other to create a
spark gap. Using a piece of .001 inch brash shim stock, I adjusted the
gap to be .001 inch. I am thinking that if 80V is supposed to jump a
.004 inch gap, then 80V should have no problem jumping a .001 inch
gap.

I am not getting a spark. Should I be getting a spark with this set
up?

I tried using
flat ends --|*|--
pointed ends --*--
rounded ends --)*(--
with no luck.

Also, I have questions few about the relaxiation oscilator circuits
used for EDM. Why do they need a capacitor. The voltage across the
capacitor is the same voltage as the power supply. Therefore the
power supply wired directly to the spark gap should create a spark.
Or is there a difference in trying to create a single spark and trying
to create a cont. arc?

Any help would be greatly appreciated. Thank You



Can anyone tell me what use you would put "spark erosion" to that couldn't
be done by any other way?
I'm puzzled about it's advantages.