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Re: Thorated vs Pure Tungsten
I disagree with the part about a cobalt drill--my own set of cobalt bits is
rated
for hardened steel alloys and stainless steel, which is representative of most
ball bearings I've seen.
I could be wrong about this; if so, please tell me, so I don't ruin my bits on
something that I thought they could get through!
Tesla List wrote:
> Original Poster: Bill Fuller <wfuller-at-home-dot-com>
>
> I doubt that a cobalt drill will cut into a ball bearing!
>
> I've just completed an "air blast" spark gap. I used 1/4" solid carbide
> (sintered) end
> mills for the spark gap electrodes. These were broken on the cutting side
> but flat and
> smooth on the shaft end. They seemed to work good for the short time used
> them (blew
> my cap). There is absolutely no wear in the surface. The ends were not
> rounded and you
> can see some black marks all around the edge suggesting all the arcs came
> from these
> there. I'll bet rounding the ends will help localize the arc and reduce the
> dwell
> time. It would also keep the arc in the air stream. There are mounted into
> 1.25"
> aluminum bar stock with 1/2" deep concentric grooves cut into it to keep it
> cool.
>
> Any comments on using carbide??
>
> Tesla List wrote:
>
> > Original Poster: Terry Fritz <twftesla-at-uswest-dot-net>
> >
> > Today I replaced the 2% thorium electrodes with pure tungsten.
> The gaps
> > actually fired much sooner with pure tungsten?? However the firing voltage
> > was more stable.
> >
> > I think the firing voltage depends mostly on the rather sharp
> edges I left
> > on the rods. I will try to really round them out and see if that helps the
> > stability. In retrospect, the sharp edges only make high field stress
> > points. However, the thorium electrodes do seem to suffer much more from
> > ionization caused by the radioactivity and thus like to sporadically fire
> > far too early. I may end up using ball bearing electrodes to get a much
> > more stable firing voltage for the safety gaps. I assume cobalt drill bits
> > will cut through ball bearings to mount the shafts that hold them?...
> >
> > I definitely would stay away from thorium and other radioactive
> > electrodes. Pure tungsten is supposed to wear faster but the worry of
> > radioactive dust getting in one's lungs during the difficult cutting and
> > grinding of this gnarly material out weighs that. "Playing" with the pure
> > tungsten is far better than worrying about dust particles from the thorium,
> > or cesium, or lanthanum... Some claim good wear from non radioactive
> > alloys of tungsten too, but this is getting to be too complex as it is...
> >
> > http://www.arcsmith-dot-com/wni/products/tungsten/tungsten.htm
> >
> > explains much about these rods...
> >
> > I still find myself strangely drawn to the 3/8 inch diameter rods :-))
> >
> > Cheers,
> >
> > Terry
> >
> > BTW - If all elsa fails, I still have 100+ Victoreen gaps :-)...