The bike is a 1984 Bridgestone MB-2. Help with Apparent Bridgestone MB-2 in Japan (See the pic by lefthread; that's what I got)
Here's another thread. This one about the idea of drilling out the 8.6 inches of seatpost stuck in the CroMo seat tube.
Drilling out Al seatpost: Any succeses?
Anyway, I redid the hacksaw technique with some high-quality high-speed steel blades (32 teeth per inch). Over the course of a few hours I made five cuts lengthwise (great blades!). Judging from the sound, I knew had reached the steel seat tube. Also the blade was flush along the tube. With victory in sight, I pried a section from the tube using very stout, extra-long needle-nose pliers. Got about three inches off the tube and no more; same with the remaining four sections. How much force was I using? The pliers are bent; the jaws are no longer in alignment. For various reasons, I decided against drilling or reaming.
My last resort was NaOH (sodium hydroxide, also known as caustic soda and lye). Over the course of two and a half days, I refreshed the solution after the reaction had stopped, except at night. I used two table spoons of flakes per 100 cc of water for each refresh except for the finale, for which I doubled that. Man, what a chemistry show that was! After I rinsed out the tube, my wire feeler told me there was almost nothing left. I took the bike over to a work table and tapped the seat tube on a block of wood a few times and out popped the remnants of the seatpost, which I will keep as a reminder of what a PITA this whole thing was.
The paint held up surprisingly well, with just some streaking here and there. But I was going to have the frame painted anyway.
If anyone wants to know more details about how I did this, what precautions I took, and so on. Just ask.
WARNING: Caustic soda is very dangerous! Take no chances. Use extreme care.
Also see this http://www.classiclightweights.co.uk/seatpin-rest.html