HV Vacuum seals I have a vacuum port that is 8.75" in diameter, it was attached to a block of aluminum. I am machining a piece of stainless steel to make a blank for it since it is a non-standard size. What are my options on gaskets? Where would I find a mechanical drawing that would be similar, so I could draw this up? I don't want to get too low of vacuum, maybe 10^-5 Torr or thereabouts so I don't have to do a really high temp bake out.  

 A: At $10^-5$ torr the vacuum is HV, not UHV. If there is a knife edge on the flange you could use copper gaskets, which are also required for high temperature bake-outs.
Else if one surface is flat you can use vacuum o-rings, like viton, with some light vacuum grease to seal the imperfections. Usually one surface will be flat, the other has a groove for the o-ring.
Read the technical description from any of the vacuum system suppliers in order to get correct specifications for your machining for a given type of seal.
E.g., https://www.pfeiffer-vacuum.com/en/know-how/mechanical-components-in-vacuum/connections/detachable-flange-connections/o-ring-seals-and-grooves/
Also note that it may be more effective to by a new port that meets your requirements,  but it is always fun to make stuff.
A: You can also use indium or gold wire.
"Oxygen-free copper is widely used. It is easily machined and has good corrosion resistance. It is unsuitable for bakeable vacuum envelopes due to its tendency to oxidize and create scales."
https://en.wikipedia.org/wiki/Materials_for_use_in_vacuum
