EDM questions

I've built an EDM from the article in Machinists Workshop Oct/Nov 2002
pg 24 to 26.
I've been testing it out using my drill press and get either violent
pops every second or so or I end up with the wire I'm using spot
welded to the work piece. I've modified the design slightly to use
what is avalable. It's fed by 230V 50cycle single phase (standard
houehold current in New Zealand) The capacitors are 680uf 250v. Bridge
rectifier is rated at 250V 20amps.

Will most of the problems disappear if I use the slow feed on my CNC
mill rather than a nervious hand on a drill press?

Can anyone sugest what I can switch across the output leads to drain
the capacitors after I've turned the EDM off? I don't want to
accidently discharge the capacitors through the CNC or for that matter
myself.

Cheers
Mark Stacey (Still tingling)
www.cncprototyping.co.nz