Although the jury is still out a little, I've gone to graphite and tungsten rod for cylinder fusor grids, using graphite as the endcaps.
Jerry once warned me -- and I'll repeat that here -- Things labeled "carbon" aren't pure graphite, they have clay binders and such like in them, and quickly ruin any cutting tool. Dont get mixed up with "carbon" be it battery rods, pencil leads and so on, they have graphite in them, but are very not pure and the additives are poison for both tooling and vacuum systems. Hit your scounged stuff with a torch and you'll see it either catch fire from wax in it, shatter, or something worse. Graphite just gets hot.
Pure graphite, from McMaster, is the other extreme -- machines like a dream to a mirror finish right off the mill or lathe, and you get some lube on your ways doing it. But you will blow black snot for awhile, as the "chip" is a very fine dust. I've been able to bore and then turn it quite thin, and it drills all too easily; start with smaller drill than the hole you need and pull it out to let the dust clear -- the dust rubbing will make the hole bigger than you wanted.
While graphite is a good lube in air, it isn't in a vacuum -- it loses the surface hydroxyls and sub-oxides that make it slippery in a vacuum and actually becomes sticky there.
Graphite is the king of elemental materials that take high heat and stay stiff doing it. It does not seem to sputter much in the fusor environment, but I have yet to check on the mass spectrometer if it's making hydrocarbons when hit with the ions -- it does roughen up in use a little bit, so some is going someplace. If I dared, and someday I might, I would make a whole grid out of it and try that -- it has great thermal conductivity too, so the feed-through can help suck heat out of it.
Next time I have my graphite grid out of the fusor, I'll put up a picture of it in this post. Right now, it's in use and working great!