I thought I'd post this in case it becomes of some future use to someone, if one of the mods wants to give it approval and move it into the right place

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There's a few items on the internet about siezed seat posts, Sheldon Brown covers most of the options for removal. However, there is a difference between a tight seat post and a seized seat post. I've had my share of tight posts over the years

, but basically if you can grab the saddle and twist even 2mm movement out of them, they will 'eventually' come out with patience and loads of WD40.
What I'm posting here is the removal of a totally seized post. The common suggestion is to clamp the post in a vice and use the frame to twist it out. Not only can this put extreme pressure on the joints of the frame it can also cause stress cracks to the paintwork. The answer is to make sure its removed as easily as it went in!
Step one: You will need a 'NEW' 300mm long, 24tpi HSS hacksaw blade. Buy a 'good' one, there's no point in making a job even more difficult by using a cheap blade. The pic below is the state of the blade after cutting the post. Wrap a cloth and some tape around to make a padded handle. Do it on the end so that the saw teeth face backwards, so your cutting as you pull the blade out of the post.

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Step two: Saw off the top of your post. This is the moment of no return, there's no trial and error, once you cut off that top you have a completely useless frame

Cut about 1" from the top of your seat tube. Its also worth noting that the particular post I'm removing was solid aluminium for the top 4". So if your post is set very low you may need to centre punch the cut off post and drill through. Fortunately, in this case I didn't have to do that.
Step 3: The most important part to get right is the start of the cut. Best to get the frame flat. I used the kitchen worktop whilst the wife was out

It also stops all the filings falling down into your axle. Get a stool to sit on, this will take some time! Make sure you start cutting slowly, keep the blade level and square to the post so you cut at 90 degrees. You want to be taking the shortest route to the edge, no need for a detour! I had a 5" length of post to cut through, it took about 20mins to get to the photo below.

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Step 4: Slow and steady, slow and steady, keep the blade straight and use smooth strokes. It will look like nothings happening, the only evidence will be the silver fairy dust around your feet. After about 90 mins you should begin to break on through to the other side! As Jim Morrison said

Be careful with the last few cuts. This is all about 'sound' and 'feel'. Listen to the note change as the blade gets close to the end, wrap your fingertips around the seat tube where you think the bottom of the post is. (if you flick the steel tube with your nail, you should hear the note change from a ring, where the tube is hollow, to a thud, where the post is inside the tube) The last thing you want to do is start cutting through the steel of the frame. But if you feel and listen that won't happen. As you near the end the blade may start to stick, its best at this point to keep lifting the blade from the slot. If you've got a vacuum handy, suck out the debris and carry on.

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Step 5: Now your frame can go into a vice, tighten so the cut closes together and pull off the frame.

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