Beryllium Insulator Gasket

[guest]

This is a question for those who bought the Beryllium insulator off of E-Bay(3L ???).

The othe other day, I was looking at the mounting base. Obviously, its not a confalt flange. What would be a good gasket material for this ? I was thinking copper. Any ideas ??

Mark Rowley
Garage Scientist(Unlicensed)

[guest]

This might not be a convenient answer, but what I plan to do with this insulator (I have several) is to turn down the base and silver solder it to an appropriate flange. Richard Hull attached his to a conflat flange. I might try using a KF50. The base is reportedly plated brass, though I heven't nicked one of mine to find out for sure.

[guest]

Unless someone comes up with a better idea, silver solder it is ! Thanks

Mark Rowley
Garage Scientist(unlicensed)

[Richard Hull]

The base is chrome plated brass. I machined off the base leaving the skirt. I then machined open a 2.75 conflat to accept the skirt and then silver soldered the two together using non-cadmium based silver solder.

Richard Hull

[Richard Hester]

I've been thinking about this one a bit. Did you use a plain silver-copper based solder, or one of the lower temperature varieties with zinc added?. I have both types. My vacuum sense tells me to use the pure silver -copper eutectic, but the silver-copper-zinc alloy melts at a lower temperature and is less likely to spoil the plating on the brass. Which did you use.?

[Richard Hull]

I used 75-25 silver-copper. It is a Jewelry alloy.


Richard Hull

[Richard Hester]

I assume you used the black flux for this job, as the silver-rich brazing alloys have a high melting point. Real good liquidity, too, so the fit between pieces should be pretty tight. To sew a button on all this , what size tip did you use? Geez, I feel like the moocher that asks you for a cigarette, then a light as well...

[Richard Hull]

I used regular borax flux and a medium fine tip, a slightly reducing flame to avoid oxidation. I heated the big flange broadly first until near red heat and then poured th' coal to the joint as the skirt on the insulator heated fast.

You are right about the fit. It must be near perfect with zero voids or gaps. The silver flows like rain water into every contacted surface giving an incredibly strong fusion joint.

When silver soldering is done well, there is little that can compete in beauty or strength.

Richard Hull

[r_c_edgar]

Richard,

Would Indium-based solder do well here? It seems that the low melting temperature would allow one to avoid the risk of damaging the stainless steel/ceramic joint, and Indium is known as a good vacuum sealant...

--Ryan Edgar

[daniele]

why not a Sn-Ag brazing ?
Low melting point and no need to overheat the FT.
It should stay solid til 200°C at least...
Our fusors FTs shouldn't go up to this temperature in the brazed area... correct me if I'm wrong...

ciao
Daniele

[guest]

Dont use tin it will sublimate under reduced pressure and heat.
Use a brazing mixture high in silver such as jewler's
solder.

Larry Leins
Physics Teacher

[guest]

Richard,
How did you machine off the base of this insulator ? Did you use a lathe or mill ? I have both, but am worried about putting the center ceramic portion under any torque. I have this nightmare that the Beryllium would crumble under the load(or affect its internal vacuum seal).

Mark Rowley
Garage Scientist (Unlicensed)

[daniele]

please check the post "some welding"


ciao
Daniele

[guest]

WOW !!!!! Cant believe I missed that.

Thanks Daniele.


Mark Rowley
Garage Scientist (Unlicensed)

[Richard Hull]

I chucked the metal base ring in the lathe. As it turned I just bore a hacksaw up against the base ring. As it approached brak through, I stopped the lathe and hand hacksawed it through, rotating it a bit at a time. I held onto the insulator so it would not fall and hit the bed ways.

Richard Hull

[Jon Rosenstiel]

I've got one of these e-bay beryllium feedthroughs also. (Purchased from a Mr. Bill Williams). But the flange is steel, not brass!

I was looking at it last night pondering just how to fit it up to a conflat flange and got curious about the material used for the hv stud. As I was testing the stud with a NIB magnet I just happened to bring the magnet near the flange. It stuck!

For me that's good news, it means I should be able to TIG weld it to the SS flange.

Anyone else have a steel flanged feedthrough?

Jon Rosenstiel