I broke a 4-40 tap in my filing machine casting. It was for the top
cap, which is there to hold packing as a seal for the file rod, so not
that big of a deal since there are five good screws. But it feels
like a berry seed in my tooth. Aggravating.

I got Langlois' book on building a hobbyist edm, but have a few other
thoughts. I have a very nice tig welder, Miller Dynasty 200DX. In
tig mode, it'll go down to 1A DC or 5A AC, plus a pulser on dc up to
250 Hz and lots of control over ac frequency and wave form. Seems I
might be able to use it in lift start mode for edm.

I'd still need to build the carriage, stepper drive, controls, etc. I
have a Beaglebone Black which could be applied to that job. I can get
a reasonable stepper for $11 from the salvage place in town, plus some
linear bearings and a bellows coupler for not much.

Any known reasons the welder is a bad idea?

Thanks.

Pete Keillor