Re: tungsten alloys for SG electrodes?

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Finn Hammer" <f-h@xxxx>

This is how I always seem to end up making Tungsten Metal electrodes: 
(Metal as in welding electrodes as opposed to carbide as in cutting tools)

I cut the tungsten metal rod ca. 1/3 trough with a hacksaw. Repeat 3 times 
at 120 degrees on the circomference. then snap it over. That means, break 
it. Use goggles!

The hacksaw has to be used with rather slow movements and high pressure. It 
is hard to go too slow, 30 strokes per minute seems about right. The right 
pressure is so that the blade does not skid across the surface of the rod. 
Once the blade has done some skidding, it becomes blunt and has to be 
exchanged to a new one.

This leaves you with a piece of tungsten rod, which is very sharp at the ends.

Now I chuck it in the battery drill press (hand drill? power driver?) and 
rotate it rather slowly, while gently introducing it to the belt sander. I 
start putting it square into the belt, when the surface is all ground even, 
tilt it relative to the belt to produce the rounding. The rotation in the 
drill chuck ensures that the surface you make is axially true, the belt 
does the actual grinding. It is easy to produce something that resembles a 
Rogowsky/Bruce profile, but even a spherical end is easy enough to make.

If I explained this well, so that it is possible to visualize, then you`l 
all agree (now that none of us have that tool griding machine, bar Ed 
Wingate) that this is one helluwa fine way to make the electrodes.

Fast too!

Cheers, Finn Hammer



Tesla list wrote:

> Original poster: "Bunny Killer" <bunikllr@xxxxxxxxxxxxx>
>
>
> Hey David...
>
> once you get into the realm of pureish tungsten the only methods of 
> "machining" it is grinding..  and snapping which is not too precise... but 
> grinding is precise...   down to .001 inch
>
> the general rule is 1/8 inch loss on each side of the due to snapping and 
> .020 loss due to grinding loss to remove the conical/wedge produced from 
> snapping...  so the best bet is to consider a ..395 " loss on each end ( 
> worst case senerio) to make all electrodes equal....
>
> Scot D