Because I am a cheap bastard that wants to use the endcaps of my vacuum chamber as Anode and Katode, Instead of messing around with spark plugs or similar, I need an electrical insulator for my vacuum pump, because the KF16 vacuum line is all metal. Otherwise the pump would sit at 500V potential!
Buying a ceramic insulator is out of the question, and a glass insulator is expensive (could easily reach 100€, SUPPOSING that the selling company wants to do business with an individual). So, I bought borosilicate tube and set my lathe to slow cooking.
Hmmm, looks like the part, doesn’t it?
Aaaaand…it breaks. (WAS expected, it doesn’t have the proper 15º slope, for starters)
This was done with absolutely ZERO effort, just heating the glass and poking it with a graphite rod.