Allan Adler wrote:

It seems to me that if one is interested in making one's own tubes, it
must be a lot easier to machine a metal tube, seal it with flanges and
O-rings, evacuate it and have electrodes passing through the metal than
it is to learn to make reliable glass-to-metal seals. The discussion also
focuses on the large number of parameters to worry about, each of which
presumably requires a new tube. But this all metal construction presumably
makes it possible to open it up and change things in it. So this approach
seems to be more suited to experimenting with tubes if one is so inclined.

Experimenting yes, if you can leave your pump running.

But for manufacturing it is not so good. The glass-to-metal seal is easy
enough: make sure your glass and pin material belong together.

I agree that blowing a nice multi pin glass base with the pins in
correctly is not easy at all, but it lends itself well to an industrial
process.

I'd think you can buy these for custom tube work, in a specified glass.

Now, if you leave your tube connected to the pump you could even use
vacuum epoxy to seal everything.

O-rings are tricky. If you have a square channel with a round ring in,
gas will be trapped where round meets square; this air will eventually
escape. The same applies to flanges coming too close together, and
really anything that you cannot heat very well.


Thomas