On Wed, 24 Feb 2016 07:17:50 +1100, "Rod Speed"
wrote:

snip
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?

snip

I wonder how we ever coped?

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

Quite ... but it worked and potentially in a more predictable way that
this 'basin mate', mate. ;-)

Cheers, T i m