Conflat with no knife edges?

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Alen Zhang
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Conflat with no knife edges?

Post by Alen Zhang »

https://imgur.com/a/kKITKqa

I just got a leaded glass viewport from Accu-Glass Products, and the connection side has no knife edge? Can I still use this (with another flange that does have knife edges) with a copper gasket and just not tighten it as much? I have a sheet of rubber, if I have to make a gasket myself.
Alexey Khrushchev
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Re: Conflat with no knife edges?

Post by Alexey Khrushchev »

I don't think you should use this glass with a copper gasket. You won't be able to clamp it hard enough without damaging the glass. You may have problems when the camera heats up. I made a viewport just by putting a vacuum rubber gasket between the KF-50 flange and the glass sheet. I also used some good vacuum grease to seal it.
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Liam David
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Re: Conflat with no knife edges?

Post by Liam David »

That flange should definitely use and o-ring seal. Do not use a copper or hard gasket. Get a standard size viton o-ring (from e.g. McMaster or the O-Ring Store) that fits over the mounting conflat knife edge and don't bother with rubber sheet or vacuum grease. I've found that an o-ring of dash number 131 works well.
Rich Gorski
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Re: Conflat with no knife edges?

Post by Rich Gorski »

Do not use a copper gasket in this case. Your chamber will leak like a sieve. Sounds like your chamber is conflat and your Accuglass viewport is NW type. You can purchase viton gaskets that are designed to seal against the CF knife edge. These have a rectangular or square cross section. Determine the size of your conflat chamber and purchase the viton CF gasket that matches. These viton CF gaskets are available at ldsvacuumshopper.com, duniway.com and others.

A more expensive alternative would be to purchase a CF to NW zero length adapter also available at the above. Then you will be mating CF to CF and NW to NW.

Rich G.
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Alexi Hammond
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Re: Conflat with no knife edges?

Post by Alexi Hammond »

This flange doesn't need any seal because it is not a viewport. It is a viewport shield and it goes on top of a regular glass conflat viewport.
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Cassio_Alvarenga
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Re: Conflat with no knife edges?

Post by Cassio_Alvarenga »

Use Indium metal seal: https://www.cmr-direct.com/en/how-to-make-indium-seals

By the way, look at the photo you posted, the glass-to-metal seal of the viewing window was made with indium wire, you can see the end of the indium wire that simply slips out when assembling in the press.
indium.jpg
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Liam David
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Re: Conflat with no knife edges?

Post by Liam David »

Details about the construction and purpose of this flange can be found here: https://www.accuglassproducts.com/viewp ... ass-shield. I did not find a different type on the Accu-Glass website, so I'm pretty sure this is it. Alen will have to clarify.

It's made to go over a standard viewport and not made to be the vacuum barrier. One might be able to use it as a vacuum barrier depending on the diameter of the glass and its relation to the knife edge of the chamber flange.

The little tabs that Cassio thinks are indium are probably just the 3 tabs that hold the glass to the flange against a viton gasket.

In any case, either get a standard viewport and mount this over the top or use a viton o-ring (and only a viton o-ring) to mount it directly to the flange. Pressure rating in the latter case not guaranteed.
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Cassio_Alvarenga
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Re: Conflat with no knife edges?

Post by Cassio_Alvarenga »

You got a point Liam, or it can be a "circlip".

Alen, if the glass is easy to remove and you have acess to a lathe, I think you can simply take the glass of and make the knife edge for copper gasket (or an grove to o-ring) screw the flange and mount the glass window last.
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Richard Hull
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Re: Conflat with no knife edges?

Post by Richard Hull »

I have used indium seals for years. You have to watch the temperature though in fusor work as indium melts at low temperatures. My first fusing fusor had a homemade glass view port and indium wire was used to seal that window to homemade flanges. Worked great! (see image)

CMR really charges for indium wire!! Whew! I worked with a local rare metals fabricator to work out a process for pulling Indium wire through a homemade die. Tough stuff. You need to heat the indium for its plastic range and slowly piston press the metal through the die at an experimentally determined rate, and without applying any pressure to the exiting wire, air cool it quickly and run it through a special oil and onto the spool.

Clean, fresh pulled indium will molecularly bond to itself with almost no pressure! Rolling clean indium wire onto itself would result in a solid block of indium on a spool!

There is an app on the Indium Corporation of America's website for teaching how to achieve solid molecular bonding indium to indium. It was used extensively on flat screen plasma panels to achieve vacuum tight glass to metal seals. Coat the glass screen edge, coat the metal frame flange, clean the indium on both surfaces, lay the glass down and pull a vacuum the pressure forced a forever seal, indium to indium.

Richard Hull
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This is hard way to make a viewport, but it worked back in 1998.  Homemade flanges using indium glass-to-metal seal.
This is hard way to make a viewport, but it worked back in 1998. Homemade flanges using indium glass-to-metal seal.
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Alen Zhang
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Re: Conflat with no knife edges?

Post by Alen Zhang »

Thank you all very much for your input. Yes, that Accu link is correct. I have decided to use it in its intended way, and place it over a regular viewport.
Matt_Gibson
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Re: Conflat with no knife edges?

Post by Matt_Gibson »

Your eyes will thank you!

-Matt
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