Hand saw with depth stop?

Neil

Heating or freezing rarely works with stuck seatposts, as most are ally to steel or ally to ally, so there's nearly always galvanic corrosion involved, which heating and freezing won't break. Trying to get a liquid such as Plus Gas in between normally helps break the bond, but force is also invariably required.

Electrolysis ? There would be a reaction between the ally and the steel - just need to get the +/- the right way around. What would be a good electrolyte - Coke Cola ?
BobH

If you want to try a Slide hammer, why not make up an expanding arbor, (OD for last 5 or 6 mm JUST less than Seat Tube, the remainder 2mm less than Seat Post. Bore a an internal taper in the large end of the arborl (before making at least four slits in about 25mm long) and then bore through to clear whatever size of stud you choose. Tap a plug, tapered on the OD to match the taper bored in the expanding arbor, and screw in some studding, say M10 or M12.

Screw the tapered plug onto the studding, thread the expanding mandrel over it, with a nut just above, and gently knock through the Seat Post. Apply the Slide Hammer to that, whilst possibly applying a heat gun to below where the Seat Post ends. Hopefully, the heat will creep up the Seat Tube, and expand it slightly while the Slide Hammer is used to try to extract the Seat Post. The Slide Hammer will apply the force suddenly, which can be more effective than a constantly applied force.

If you don't fancy risking the paint by applying heat, do persist with the penetrating oil before using the Slide Hammer set up. Once things start to move, apply some more juice and resume Slide Hammering.

Good Luck

Howard

Wow many thanks guys (wot no ladies?) there are some good suggestions there. This one is now out (not mine) apparently it was the carefull saw method. I will try the dowel to prevent crushing next time and look for those plastic clips or bend steel round the blade. One I did recently was steel to steel and I ended up using caustic soda, even then it was so badly welded in I could not get the remainder out with a chisel and eventually got enough out to put a shorter post back in. Oh and paint it of course. Once again thanks for your help.