On Fri, Aug 29, 2014 at 5:48 AM, John Griessen  wrote:
> On 08/29/2014 03:29 AM, Nathan McCorkle wrote:
>>
>> looking to make a vacuum container wire feed-through, thinking I'll
>> drill a hole into an existing aluminum blocking plate
>
>
> How about buying a ready made terminal with plastic around it to silicone
> into
> a hole in a plate, or hole in a rubber stopper?

All the terminals I've seen that mention anything about vacuum or
hermetically sealed seem to ring-in in the hundreds of dollars.

Also I'd like to try and keep the chemical list down to a minimum, as
certain materials like to off-gas for a very long time and that
behavior can foul the vacuum and imaging system contained therein.

>
> Or, the spark lighting electrodes from gas grills (like piezo sparkers come
> from)...

Hmm, I haven't look at one of those in a while, I've got a box of
gas-leaked-out piezo hand-held lighters but they've just got a
plastic-insulated wire. Do you have a certain brand?

> They look like a glass to metal assembly that might be fairly hermetically
> sealed
> just by accident...  They're 0.25 inch diameter and would fit in a stopper
> hole also.
> I think there's one of those just down the street at the moment...

I'd really like to try the Viton stopper approach, NASA seals walk-in
vacuum chambers with doors >15ft wide using Viton o-rings (or used to
at least). The rest of the vacuum system uses Viton, which may not be
required as this doesn't go through temperature swings or harsh
chemical treatment. But I have only really scratched the surface on
o-ring vacuum sealing technology, so I'm not sure which rubber
compound would be second-best (in terms of how flexible, and also in
terms of off-gassing). I know off-gassing can differ between different
kinds of RTV silicone, as I've researched the various types of those
available for potting electronics.

I'll take a look at the grill lighters for sure when I go to the
hardware store to look for stoppers.

Thanks!
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