On Wed, 22 May 2019 17:56:17 -0700 (PDT), "
wrote:

On Wednesday, May 22, 2019 at 7:50:50 PM UTC-4, Ed Huntress wrote:


John, can you give us a general idea of what the "fairly easy" EDM
power supply is like?

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Ed Huntress

It has been a long long time ago, but what I remember is that we used an isolation transformer with a dipper and bucket voltage doubler connected to the output. So that would be a transformer, two diodes, two film capaciters, and maybe a resister to limit the current when ( not if ) the electrode shorts to the work. We used a wooden dowel in the drill press so the drill press was not hot. We used the drill press spindle stops as a rough adjustment and just leaned on the spindle for the fine feed. Crude but it worked.

Dan

OK, that's a basic type of old tap-buster circuit. I wondered if John
had anything in there to prevent arcs and sticking. Those simple
circuits tend to weld the elctrode and work together if you don't have
a really good touch.

If he's using 4H pencil lead I think he has a hell of a lot of
resistance in the circuit. That does limit the arcing and welding.

Anyway, these can be a good way to erode a piece of hardened steel,
but my experience with commercial ones is that they're bog slow unless
the mork is very small -- like a set screw.

BTW, the commercial ones generally *drop* the voltage, not double it.
But that would depend on the rest of your circuit, including the
electrode. They usually use copper or another metal..

--
Ed Huntress