T i m wrote
Rod Speed wrote
T i m wrote

If the rubber had a thread that matched the waste outlet
at rest, then you compressed it 50% of it's original size,
what pitch would the thread be then.

The compression doesn't happen that way, it sees the rubber
compressed into the metal thread and that is what seals it.

But I'm told there is a thread inside the rubber?

Because that gets more rubber into the metal thread
because the threads match.

I wonder how we ever coped?

By using the much cruder approach of a sealant of some form or other.

Quite ... but it worked

Doing it the other way works much better.