Unwelding/Fusing a bike seat from the frame

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Hey guys,I have a problem I need help with, as I have next to no experience with metal working. I came across a guy here in New Orleans who is refurbishing vintage bikes. He has a couple from Japan and Germany that (he said) has an an aluminum seat insert fused into the steel frame. That's how they were made as opposed to these days, which normally the seat insert slides in and out of the frame allowing for adjustment. He says he has tried everything including dry ice to get the insert removed from the frame. Unless he can get this doen the frames are useless, but i'd really like to be able to get one up and running. Are there any techniques out there anyone would sugget without hurting the frame? I was thinking maybe using a hole saw drill bit about the diameter of the aluminum, although I was concerned about the dammage not to mention that it would probably take forever!let me know guys,Thanks,- Chad
Reply:This covers all the bases:http://sheldonbrown.com/stuck-seatposts.htmlSlap some anti-seize on whatever post you reinstall.
Reply:The link that farmall provided looks pretty good.  If none of those suggestions work, sadly there's only one final option. A plasma cutter to the frame. Then a good weld back repair job followed by body work and paint. "Hey I didn't come to look and learn, I came to turn and burn.... If I can't light up, I'm gonna light out!"-JodyIdealarc 250 "Fatman"MM 252MM 211 "Little boy" Victor Torches
Reply:Originally Posted by farmallThis covers all the bases:http://sheldonbrown.com/stuck-seatposts.htmlSlap some anti-seize on whatever post you reinstall.
Reply:bert the welder said the easiest rout get a big twist drill of a close fit off of ebay should be less than 20.00 or harbor freight and then cut the aluminum off flush with the steel frame and start drilling. The aluminum is softer and the bit aught to follow the steel tube if you are up to it should be able to do it with a hand drill low RPMs. will not be fun but doable.Do not argue with an idiot. He will drag you down to his level and beat you with experience.
Reply:I've actually chopped them off at about 4"above the frame, & used a sawzall straight down the seat post making a vertical slit on 12:00 & 6:00 positions. I'll usually tack a piece of stock to both pieces just so they don't slip downward once cutBuy American, or don't whine when you end up on the bread line.
Reply:Strong acid or alkaline liquids usually attack aluminium severely, but are quite a bit less damaging on steel. Might be a route worth investigating.
Reply:This happens quite often. The folks at Retrobike.co.uk/  have many clever solutions. One of them using diet coke to disolve the seizure. Mention where you were recommended from and you will get lots of help be sure to name the brand of bike if you can.Last edited by shovelon; 04-22-2012 at 09:46 AM.Weld like a "WELDOR", not a wel-"DERR" MillerDynasty700DX,Dynasty350DX4ea,Dynasty200DX,Li  ncolnSW200-2ea.,MillerMatic350P,MillerMatic200w/spoolgun,MKCobraMig260,Lincoln SP-170T,PlasmaCam/Hypertherm1250,HFProTig2ea,MigMax1ea.
Reply:Originally Posted by idacalbert the welder said the easiest rout get a big twist drill of a close fit off of ebay should be less than 20.00 or harbor freight and then cut the aluminum off flush with the steel frame and start drilling. The aluminum is softer and the bit aught to follow the steel tube if you are up to it should be able to do it with a hand drill low RPMs. will not be fun but doable.
Reply:cut the post off and slit the aluminum from the inside with a hacksaw blade, then pry,twist, and pull till the post comes out
Reply:I think both the sawzall or hacksaw would work. I'd be tempted to go 12, 3, 6, and 9 o'clock. But don't get to gung-ho with the prying. This ain't gas pipe. Probably pretty thin. Still hoping he posts pic's. *popcorn......*200amp Air Liquide MIG, Hypertherm Plasma, Harris torches, Optrel helmet, Makita angle grinders, Pre-China Delta chop saw and belt sander, Miller leathers, shop made jigs etc, North- welders backpack.
Reply:That's if it's corrosion seized.  Originally Posted by shovelonThis happens quite often. The folks at Retrobike.co.uk/  have many clever solutions. One of them using diet coke to disolve the seizure. Mention where you were recommended from and you will get lots of help be sure to name the brand of bike if you can.
Reply:Originally Posted by bert the welderThat's if it's corrosion seized.
Reply:I would try a pencil grinder and carbide burr , that is if its not too far down in the steel tubing.. are you sure its not pinned together anywhere?Last edited by brucer; 04-26-2012 at 03:08 AM.tackleexperts.comwww.necessityjigs.comhttps://www.facebook.com/groups/mach...dingequipment/
Reply:Hole saw?  Nope, not likely.Whether the aluminum seatpost is corroded in place or purposely put into the steel frame with a shrinkfit, removal is pretty much the same.  Mechanical means or chemical means.Strong alkali will dissolve aluminum and not have much effect on the steel, but will strip or damage the paint.Mechanical choices using various abrasives or cutters to remove the aluminum will work, don't just go in and try to go too fast and out of control and then end up wrecking the steel frame.Pretty much covered in the link above from Sheldon Brown's site.  The best laid schemes ... Gang oft agley ...
Reply:Carbide burr on an extention, the Al is soft and will clog the burr up, clean it up as you go  and grind the Al post out of there.  Course then ya got the second problem of putting a new one in and holding it in there?Bikes are cool, you've got our attention... we like weird stuff like this... ok, now fork over the PICTURES or we'll go away boredLincoln Power MIG 215Lincoln WeldPak 3200HDLincon ProCut 25Lincoln WeldanPower 225 AC/DCIf all else fails... buy more tools
Reply:Sure, but we are talking on purpose here, I believe. I a case of galvanic or corrosion, would the coke penetrate seized seat post ya think? Come to think of it though, it is nasty stuff. Guess if it did, it would be a BB repack.    Originally Posted by shovelonI am thinking it is galvanic corrosion.
Reply:Papa, I fear he may be a one hit wonder. I really want to see this frame.200amp Air Liquide MIG, Hypertherm Plasma, Harris torches, Optrel helmet, Makita angle grinders, Pre-China Delta chop saw and belt sander, Miller leathers, shop made jigs etc, North- welders backpack.
Reply:I wonder are we talking Al/Fe interaction chemically or this a swollen upstem from heat and then install the Al seat pipe... I've never heard of that but who knows... Schwinns for me, the older the better... How U been Bert haven''t seen a post in awhile?Lincoln Power MIG 215Lincoln WeldPak 3200HDLincon ProCut 25Lincoln WeldanPower 225 AC/DCIf all else fails... buy more tools
Reply:Let us know if any of the above works.  I had the same problem once, two bike shops told me it was a common problem and they have never heard of a way to free up a stuck post.
Reply:Originally Posted by PapaLionI wonder are we talking Al/Fe interaction chemically or this a swollen upstem from heat and then install the Al seat pipe... I've never heard of that but who knows... Schwinns for me, the older the better...