[Milsurplus] How Much Vacuum in "Vacuum Tubes?"

[J Forster]

Essentially yes. I think the evacuation stem is heated and then 'pinched
off' while hot and soft then possibly heated more to completely seal the
end. It's akin to 'flame polishing'

-John



How do you seal the tube while under a vacuum?

Is the seal stem itself hooked to a vacuum pump, and when the vacuum is
down to the
level desired, the stem is heated by an external heat source, the stem
melts and
seals while the vacuum is still being pulled by the pump?

I get dense on what is probably very simple.

73
Sheldon