Before you call me stupid and say this is impossible, just hear me out:

I saw this graph before that really intrigued me, It included many types of vacuum pumps and their approximate starting and ending vacuum. Obviously with just a mechanical pump can start in atmosphere, but can’t get into high vacuum. Typically a turbomolecular or diffusion pump is turned on once the mechanical pump brings the vacuum low enough for them to become effective, and these pumps bring you into high vacuum. But, according to the graph, the lowest vacuum that a mechanical pump can pull is also approximately the point where titanium getter pumps can be used. In case you don’t know, these are just big consumable titanium filaments in the vacuum chamber that act as a getter once turned on. These (according to the graph) can bring you well into the high vacuum necessary for vacuum tubes. I can’t find the graph now but if I do I will put it in the comments.

So, here is my plan.
1) Make all elements of the vacuum tube as normal, but add one extra wire feed through in the borosilicate pinch seal.
2) Connect a small coiled titanium wire between one of the filament leads and the extra lead in the pinch seal, out of the way of the tube elements
3) Continue tube construction as normal and get the tube pumped down and baked with just a normal mechanical pump.
4) Heat the titanium filament in the tube for a little while to get the vacuum in the envelope as low as possible.
5) Seal the tube and separate it from the vacuum system, let it cool as usual.
6) Heat the titanium filament some more until the tube operates as wanted.
7) If the performance ever gets a little shoddy, just heat the titanium filament again as needed throughout the life of the tube.

This plan doesn’t require an induction heater, doesn’t require expensive high vacuum equipment, and is very very beginner friendly. Even if you didn’t outgas the tube properly, or maybe there was some small mount of residue inside, this allows for re-getting(?) to compensate for poor craftsmanship.

What do you think? Maybe some of you will shoot this idea down, but it’s worth a try.

Without baking out your metal parts you will get very poor quality electron tube. Having high residual gas pressure and behaving partially as a gas filled thyratron, with high noise and hysteretic characteristics.

@RRK
Ok... Assuming I did that, then, would this be ok? Is that the only issue with this procedure?

I can predict that making good quality DIY seals with boro/Pyrex glass will be a big PITA. That means using tungsten wire with all associated problems.

Properly baking out your tube is relatively easy. Do not skip this step, it is really significant.

Also you said nothing about cathode preparation. If you plan to make an oxide cathode, it should be activated at some step.

I think getti getting some induction heater will become more "beginner friendly" than complications like more complex seals (with more wires).
As induction heater you can find those "induction torch" guns intended for heating stuck bolts and nuts,... These became quite affordable recently, but this could be too much power.
Or there are many "ZVS induction heater" kits on various sites, more in the power range for heating small metal components.

@RRK
I have found a source of Kovar wire, so making the seals should be somewhat easier, but yes this will still be the difficult part. Obviously I would come up with a way to bake the tube, every resource that I can find says that is a good idea. I would also use a coated cathode, I didn’t specifically include that in the steps but that would definitely happen. I am mainly just asking about the need for high vacuum pumps, other aspects of vacuum tube construction are very familiar to me.

@Medved
Too powerful? I thought because of their small size that they would be not powerful enough, but if they will work that would definitely be easier than making another feedthrough. They definitely are relatively cheap.

for doing home-made vacuum glass devices, I came across this website many many years ago, which I am pleased to see is still up

http://www.teralab.co.uk/Glass_Blowing/Glass_Blowing_Menu.htm

well worth giving the articles there (and the rest on the websites main page) a read

@LightBulbFun
Wow, that is an excellent source. Interesting to see soda lime glass use, but the zeolite annealing bin is probably the only way you can get away with this. The site shows the use of magnesium getters, which are not very effective, but the glassblowing techniques shown are very very useful.

So I am assuming this proposed technique is good, anyone else have any objections?

There are multiple kinds of borosilicate glasses sure, but by default one expect Pyrex-like COE 3.3 borosilicate glass, a staple in a lab glassware, crafts and even some European sign tubes. Again, there are multiple versions of Kovar, but usually having about COE 5. You won't get a good seal between them.

There was so called molybdenium glass, it was popular in USSR for some reason, having COE of 4.9-5.2. But it is tricky to work and I doubt you will find a reliable source today.

 

@LightBulbFun
Wow, that is an excellent source. Interesting to see soda lime glass use, but the zeolite annealing bin is probably the only way you can get away with this. The site shows the use of magnesium getters, which are not very effective, but the glassblowing techniques shown are very very useful.

So I am assuming this proposed technique is good, anyone else have any objections?

Most of the time you can get away with carefully flame annealing your object. Using perlite or vermiculite can cause problems if some small grains accidentally get melted into the seal.