T i m wrote
Rod Speed wrote

but, if you compress something rubber that's
threaded ... what happens to the thread pitch ... ?

Nothing, because the compression is of the
rubber thread into the metal thread, not in the
other direction where it affects the thread pitch.

And how do you think that compression happens?

Like I said, by the compression of the rubber
thread into the metal thread, not in the other
direction where it affects the thread pitch.

Chicken and egg my friend.

There is no chicken and no egg and you aren't my friend either.

Now, it's quite possible that any thread on the rubber
could be designed to match the thread on the waste
when the rubber is compressed to some typical value
but if you have ever tried 'pushing' (rather than screwing)
a thread into place, especially when the other half of the
joint is metal and sharp, the 'threads' may not actually
drop into place (potentially making the seal worse).

Even sillier and more pig ignorant than you usually manage.

Translation. I'm busted and don't have
any sensible reply or explanation.

Just another of your pathetic little drug crazed fantasys.

And doesn't explain why so many found that it
sealed fine without the use of any sealant at all.

And many *also* used sealant that could
well have done the job on it's own.

With a lot more farting around and mess.

Nice theory, pity about the real world.

See above.

Completely useless, as always with your ****.

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.

I'm not sure there is a better on 'working fine'. ;-)

Corse there is when you don't have to fart around with any
sealant at all, just assemble it and find that it seals fine.

After you have gone out and found someone who
stocks the 'Basin mate' and bought one you mean?

Corse you never have to do anything like that with sealant, eh ?

Rod, you know most people have you killfiled

Corse no one ever does anything like that with you, eh ?

and so I'm asking for trouble by talking to you here.

Even sillier than you usually manage.

I only do so whilst you remain reasoned and reasonable.
As soon as you stop (and you often do) I stop talking to you.

I couldn't give a flying red **** what you do about anything.

Nothing you have said on this matter changes, or will change
my real-world understanding of how things like this work.

True of your **** in spades.

One thing I can be 100% sure of. Set up two basins, add the waste
to one conventionally (using sealant) and the other using the 'Basin
mate'. Once the one using sealant has been allowed to cure (if
required), test both using the worst case scenario of the waste
blocked and the sink filled to the brim. I know the one fitted
traditionally will not leak, I wouldn't bet any money that the
other wouldn't (although it may well not).

Your problem, as always.

Would you put £1000 on it?

Yep.