On Wednesday, May 22, 2019 at 9:26:53 PM UTC-4, Ed Huntress wrote:


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.

We had the work submerged in kerosene and had no problem with sticking. I can not remember if we used the carbon from a flashlight battery or a nail.



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.

For a one time need , slow was better than nothing. For something used regularly, a stepper motor drive and a micro controller would mean you could set it up and then do something else.


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..


We did not double the voltage. Just used a voltage doubler circuit. The actual voltage depended on the voltage required to arc.

Dan


--
Ed Huntress