Re: Inside A Plasma Cutter (Must See Pictures for SSTCers!)

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux" <jimlux-at-earthlink-dot-net> 

 >
 >      Actually, there is something on that site that might be pertinent to
 > SGTCs.
 >
 >      "The biggest problem with air cutting has always been the rapid
erosion
 > of the plasma torch electrode. Special electrodes, made of zirconium,
hafnium,
 > or hafnium alloy, were needed since tungsten eroded in seconds if the
cutting
 > gas contained oxygen. Even with these special materials, electrode life
using
 > air plasma was much less than the electrode life associated with
conventional
 > [inert gas] plasma."
 >
 >      Anybody use zirconium or hafnium alloy electrodes in their spark
gaps?
 >      Kinda surprises me, given the pyrotechnic uses for zirconium metal.

Zirconium has a high melting point, too, so maybe that's why they were using
it?
The oxides of all those metals withstand very high temperatures too, and in
crystalline forms, have fairly high thermal conductivity.  I don't know
about electrical conductivity.

The electrode life in our Thermal Dynamics  was quite long.  I only recall
replacing electrodes once or twice in 4-5 years, and that was usually
because they got gunked up because someone had cut something like auto
underbody panels with that asphalt-like coating on them.  As the web site
says, plasma cutters revolutionized metal working shops, particularly like
ours (building gear for special effects).  The plas cutter was a very handy
tool for cutting up panels in a car that you were reinforcing for instance.
I don't know that I'd use it as a replacement for a chop saw on tubing, but
for sheet metal of any kind, it's definitely the tool of choice (perhaps not
on Aluminum plate.. it cuts a bit too fast, and leaves a ragged edge).