John,

I have a big bathtub for once in my life and I want to remove the
Drain Flange.
I started to unscrew the flange and after a few turns I could see
that it was only caulked in.
I kept screwing it off but to no avail.
What is holding down the Flange???
I can put a screwdriver down the hole of the flange and feel that it
just elbows once i get beyond the flange.

First, the tub itself is not threaded. The flange usually threads into
the elbow below "sandwiching" the tub in-between the two.

Also, plumbers putty is the usual water sealant underneath the flange,
but silicone caulking wouldn't be unheard of (some manufacturers
recommend it).

Assuming the tub is plumbed in the standard way, you probably have a
combined "waste and overflow" assembly. This is the tub drain, the
overflow assembly on the side of the tub, and the pipes and fittings
connecting the two. You may want to visit a home center to see how new
ones go together.

Waste and overflow assemblies are usually made of plastic, unless they'll
be exposed for some reason (like a standing clawfoot tub).

My first guess would be the threads on the elbow fitting are stripped. If
so, you're probably not in an easy situation. Somehow you'll need to get
underneath the tub (hopefully it's over a basement or crawlspace) and
replace that part of the tub overflow. You'll probably need help
reinstalling the new one. Someone to hold up the fitting from below, and
someone to carefully tighten the flange from above.

A second possibility would be a nut on the bottom of the bathtub drain.
Once you loosened the flange, the nut is now able to spin around freely.
You "might" be able to loosen it by pulling up on the flange as you
unscrew it, but eventually the nut on the backside will drop away, and
you'll still need access from underneath to reinstall it.

A third possibility is the flange is already loose, and you're just
twisting the silicone that is gluing it down. If it has a tendency to
"spring back" when you release it, I would suspect that's partially the
cause. You might run a knife carefully around the bottom of the flange
and try cutting the silicone away. Then see if the flange will lift away.

Regardless of the cause, you are more than likely going to need access to
the bottom side of the tub. If this is over a crawlspace or an unfinished
basement, it's probably no problem. Or, if you have an access panel on
the front of the tub or through the back of the wall on the drain end of
the tub, you might be able to get at it that way. Otherwise, you're
probably looking at opening the ceiling below the tub, or through the
backside of wall on the drain end of the tub.

Good luck!

Anthony