Removing a stuck seat tube

[Seascaper]

I have an Audax MK3, the seat fortunately is at my correct height but it is stuck in the tube. I have added a lot of penetrating oil but probably due to tube length it wont budge. As a final method I am considering drilling a couple of 9/10mm holes through the tube to allow me getting a bar through for added leverage. Has anyone had this problem and solved it. I don’t want to heat it up as it would damage the pain. The frame isn’t very old.

[PH]

First thing I'd try is riding it with the screw removed, bumpier the road the better.
If that doesn't work, then with extreme caution and at your own risk:
Thread the screw in from the other side.  Put a coin, or some other flat metal object, between the two lugs. Once it's tight enough to hold the coin, an extra half a turn. Wrap some tape around the slot so it's sealed. Spray With Plus Gas (Other penetrating oils are available, but they're not all equal), leave for 24 hours. Tap it down with a rubber mallet, don't whack it, twenty or so taps, you're only trying to break the grip, a few taps at 45 degrees won't hurt.. If it moves, add more Plus Gas, wait, and try pulling it out, twisting, don't force it. more plus gas if it's moved but not free.  If it doesn't move, another half a turn of the screw and repeat. Don't overdo the screw, if there's a gap between tube and seatpost, there is no advantage increasing it. Plus Gas works, you just have to get it where needed and give it time.

[in4]

Along with the coin advice perhaps a few squirts of GT85 might help. Widely available in UK.

[B cereus]

It's worth pursuing non destructive methods before resorting to more drastic action. Don't be afraid to use heat.

An effective technique is gentle heat in combination with a good penetrating oil like Plus Gas. The aim should be to heat the seat post to a temperature around the boiling point of water. This will drive off the water of crystallization from the corrosion products that are bonding the seat post to the seat tube, and should loosen the bond.

A hair dryer, or hot air gun used very carefully, should suffice. Use alternate cycles of penetrating fluid and heating. A sign that you're winning is seeing steam being driven off during the heating cycles.
 

[mickeg]

As B Cereus noted, a hair dryer can be a good source of heat.

I would certainly trust using it for several minutes at a time, but not for extended time.

A hair dryer is designed to be used for a few minutes at a time.  Leaving a hair dryer on for much longer could damage the hair dryer.  I set a hair dryer on something to provide a continuous steady source of low level heat at a low setting, after about 10 or 15 minutes the hair dryer quit running, and never ran again.

I used a hair dryer to warm up my frame bottom bracket shell before I used significant force to remove a stuck bottom bracket that I wanted to remove from the frame.  I can't say if the heat helped or not, but it certainly did not hurt.

[JohnR]

The coefficient of thermal expansion of aluminium (the likely seat post material) is about double that of steel (the frame) https://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html. I wonder if some freeze spray eg https://www.amazon.co.uk/MOTIP-Freezer-Spray-500-ml/dp/B015XMVM7E on the seat post might encourage it to shrink and break the bond or temporarily increase of chance of penetrating fluid getting between the two metals.

[Binky]

As always, Sheldon (R.I.P) has the answers:
https://www.sheldonbrown.com/stuck-seatposts.html

I fought a 3 week long battle with a secondhand Fuji Track frame and seatpost a few years ago, I tried WD40, Plus-Gas, gearbox fluid and acetone mix, clamping the seatpost in a bench vice and turning the frame, then tried dissolving the seatpost with caustic soda (aluminium post in a steel frame) with no joy. Eventually I bolted 2 hacksaw blades together, cut the top of the post off and after several slow and careful sessions managed to cut the post into 4 strips from the inside, grip them with mole-grips and twist/pull them out. I now have the remains mounted on a plaque in my garage to remind me that greasing seatposts is part of regular maintenance.

You mention trying to get more leverage but not what leverage tricks you've tried yet. If you have an old scrap saddle try putting this on the post, you can then hit it, twist it, put it in a vice etc without worrying about damaging your good saddle.

Personally if I couldn't shift a seatpost after a few days soaking and some leverage, and the frame was a nice one that I didn't want to risk damaging, then I would now send the frame off to a specialist. There are companies out there with a pulling machine that will safely remove it for £80.