Buy an expensive sharpener if you want, but ...
I've always wondered what all the fuss was about to be perfectly honest. I chuck my tungsten in a keyless chuck electric drill and simply hold it up to a linishing belt (a sanding disk would work just as well). Even the smallest electrodes are more than stiff enough at full length as the belt is running away from the tip. Just chuck the electrode in, keep the rpm of the drill low and literally in 1-2 seconds the electrode is resharpened and good to go. If you really want to be anal about contamination, reserve a belt or disk just for this purpose, slip it on and sharpen a bunch of them at one time, then re-hide the belt.
Total cost? Zilch.
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