How airtight is PTFE?

Hello, Instead of a single O-ring, I'm planning on using a turned conical teflon seal glued to a steel shaft. The seal will push against a conical
steel surface under high pressure. Considering the surfaces are very smooth (Rz < 0.5), can I assume that the junction will be airtight?
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loquak wrote, On 8/9/2008 2:48 PM:

How much pressure are you talking about? How big is this seal going to be (what is its approximate diameter and thickness)?
The problem with Teflon is that is subject to cold flow when under pressure.
You might want to consider some sort of metal to metal seal like a flair fitting. See:
http://www.worldwidemetric.com/PDFs/CAST_SAE_J514.pdf
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Paul D Oosterhout
I work for SAIC (but I don't speak for SAIC)
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