Originally Posted by 3alarmer

I know you've already tried heat, snow, and PB Blaster, but while you still
have something to grab in a vise and twist on, get some CRC Freeze Off at
an auto parts store, heat the post one more time, with a heat gun or torch
(being mindful of the painted seat tube), and then hit the post at the insertion
point and up and down the tube slot with the Freeze Off.

You need a vise that will not slip, so before doing this, find one that will not move at all.


Otherwise, if this fails if the post is not in too deep the hacksaw method works.
(You attach a small washer to the free end so that it can ride along on the seat tube
past the post bottom and not cut into the frame tubing.)

If you can find a frame guy and talk nicely to him, you might find someone willing
to ream it out for you. I've never tried that one, myself.

The hacksaw thing is a method for the patient and methodical, and is quite laborious.