Only works on posts with open topss, only works on frames with large cutouts in the B.B. shell, probably only really safe to use on steel frames and even then...
There are other, better methods which use intelligence (and/or chemistry) rather than brute force to overcome the seatpost-seattube bond.
To clarify, this is a steel frame. I've already cut the top of the seat post off. I feel that the gentle force provided by the physics of this method is cleaner than chemicals. I don't know. I just wanted to know if anyone had tried it.
Before I try caustic soda, has anyone tried this?: http://bikesfornoreason.blogspot.co.uk/2015/01/the-seatpost-from-hell-how-to-remove.html
This makes total sense to me, but seems to good to be true. Any thoughts?