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Old 12-30-13, 10:08 AM   #1
ppg677
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last resort for stuck seatpost, dissolve with lye or cut?

I'm trying to salvage a Trek 613 frame, with one heck of a stuck aluminum (fluted) seatpost.

I've tried bench vise (well the best I can given that the vise wants to rotate under very high torque no matter how hard i tighten the vise).

I've tried ammonia for 30 hours.

I've tried PB Blaster.

I've heated it up the post with propane twice, my most recent effort I then stuck the hot post in the snow (its -16 Fahrenheit today) and then I immediately tried bench vise.

Seems my next options are either cutting it out with a hacksaw blade (maybe finagled to a broom stick dowel) or to dissolve it out with lye. Which option would you chose?
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Old 12-30-13, 10:34 AM   #2
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I had the same problem on a Trek 520. After exhausting all a Sheldon Browns tricks, I used lye. The lge worked, but the heat from the reaction ruined the paint. Use extreme caution when using lye, it can blind, and burn!!!

Cheers,
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Old 12-30-13, 10:41 AM   #3
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I had 6 inches of stuck (don't go there!). Used Kroil available only on the internet. hit it from both ends and let it sit for a couple of days. Broke free with a little heat on the post only. Took some effort.
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Old 12-30-13, 10:53 AM   #4
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I had an old fluted seatpost stuck so tight the bike shop said it was permanent. Took the bike into the farm shop and a bigger vise and we got it, but it took some serious beating, extender handles, and 2 stromg guys working on it. As luck would have it it was a 1980s steel framed MTB. Wouldn't want to try that on an aluminum or CF frame bike.

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Old 12-30-13, 11:50 AM   #5
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Know someone with a drill press? you can cut it off then bore out most of the post with a 1" drill.


one of my friends broke the brazing of the seatstays twisting the frame,

so then damage done got the torch out, frame red hot it came out,
then he rebrazed the seatstay tips.

Last edited by fietsbob; 12-30-13 at 01:13 PM.
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Old 12-30-13, 12:06 PM   #6
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I know you've already tried heat, snow, and PB Blaster, but while you still
have something to grab in a vise and twist on, get some CRC Freeze Off at
an auto parts store, heat the post one more time, with a heat gun or torch
(being mindful of the painted seat tube), and then hit the post at the insertion
point and up and down the tube slot with the Freeze Off.

You need a vise that will not slip, so before doing this, find one that will not move at all.


Otherwise, if this fails if the post is not in too deep the hacksaw method works.
(You attach a small washer to the free end so that it can ride along on the seat tube
past the post bottom and not cut into the frame tubing.)

If you can find a frame guy and talk nicely to him, you might find someone willing
to ream it out for you. I've never tried that one, myself.

The hacksaw thing is a method for the patient and methodical, and is quite laborious.
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Old 12-30-13, 09:44 PM   #7
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Quote:
Originally Posted by 3alarmer View Post
I know you've already tried heat, snow, and PB Blaster, but while you still
have something to grab in a vise and twist on, get some CRC Freeze Off at
an auto parts store, heat the post one more time, with a heat gun or torch
(being mindful of the painted seat tube), and then hit the post at the insertion
point and up and down the tube slot with the Freeze Off.

You need a vise that will not slip, so before doing this, find one that will not move at all.


Otherwise, if this fails if the post is not in too deep the hacksaw method works.
(You attach a small washer to the free end so that it can ride along on the seat tube
past the post bottom and not cut into the frame tubing.)

If you can find a frame guy and talk nicely to him, you might find someone willing
to ream it out for you. I've never tried that one, myself.

The hacksaw thing is a method for the patient and methodical, and is quite laborious.
i have used freeze off on a thin thomson masterpiece and got it out. ripped the top of the post twice but did not need to cut it out. frame was a semi custom steel. freeze off is good stuff. the hacksaw always works though
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Old 12-31-13, 06:42 AM   #8
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They lye approach is effective but can take a considerable amount of time to do it safely. When I went that route on an old SR seatpost (installed deep enough that the flutes funneled water into the top of the seat tube), a week of lye solution still only dissolved about half the wall thickness. But it was enough that going at it with a hacksaw blade after that was a much more manageable operation.

If you go the lye route, I recommend mixing the lye solution in a 1 qt Pyrex measuring cup immersed in a water bath for cooling. Dissolving pure NaOH in water releases a lot of heat, even before it comes in contact with Al. Wait until the solution is completely cool before adding it to the frame. Start with a relatively low concentration solution so you can get a feel for how much heat it's going to generate in the frame. As you replace with fresh solution (a couple times a day) you can gradually up the concentration until you hit a point where the seat tube is about 150 deg F. Higher concentrations will work faster, but you risk paint damage from the heat.

Be very careful working with the solution -- gloves, goggles, lab apron, etc. NaOH burns are no joke. Also make sure you have good ventilation and that if the seatpost lets go or the lye dissolves through it, you have something safe to catch the mess that drains out.
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Old 12-31-13, 07:56 AM   #9
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I removed an aluminum seat post that was seriously stuck in a Giant Yukon steel frame by using a long dull demolition saw blade. I cut the post off just 3-4 cm above the seat tube and inserted the blade which was sharp enough to cut the aluminum but dull enough to be very slow to cut steel. I made one cut completely through the side of the post and then three more nearly through. I used a large water pump pliers (aka Channel Lock Pliers) to crush the post in on itself and twisted. It still took some work but after the first two sections of post were free the whole thing finally popped out. The only damage to the frame was some minor scratching inside the seat tube. The whole process took about 30 minutes as I cut through the stuck post very carefully stopping frequently to inspect with a flashlight to make sure I was only cutting aluminum.
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Old 12-31-13, 08:09 AM   #10
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i agree try the freeze off: broke free a super stuck seatpost outta my friends bob jackson using freeze on the seatpost and boiling water on the seattube several times + spraying liquid wrench / tapping with mallet. took two guys turning the frame to get it to break free and twist it out of the frame
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Old 12-31-13, 08:30 AM   #11
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As a guy who makes soap, I have a lot of experience with lye and lye solutions, and I'd never put the stuff anywhere near a frame I cared about. I'd definitely try Kroil, freeze-off, and using a stronger vice before I resorted to something that caustic. This is juts my opinion, coming from a guy who has lye experience, but has never used lye on a seatpost at all...
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Old 12-31-13, 08:44 AM   #12
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AND THE WINNER IS

MYOSMITH !

add a broad flame oxygen/map gas torch followed with seting the tube into a dry ice trench ...dry ice/Al foil/DIY cardboard box.

I have serious reservations on what this does to tubing strength.

what happened in there is an addition of water and oxygen molecules to the surfaces/lubricants in space not large enough for those molecules. The molecules packed in and packed in until their packing in strength forced the tubing apart from the as newly back then inserted position.

The molecules continued packing in...until t he Universe began expanding....almost right ?

Worser, these dang molecules packed so tightly they formed an almost metallic strength INSOLUBLE compound you now attempt to mine.

if not insoluble then how would it form in the first instance ?
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Old 12-31-13, 03:29 PM   #13
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I've done the lye thing before (outside, with full rubber suit and faceshield) and wouldn't really recommend it unless you've worked with chemicals before. It boggles my mind that I can walk into any store and buy lye and other crazy strong chemicals without any questions asked. I did mine outside in the winter to alleviate the heat issues a bit. I'd plug any holes from the bottom bracket and stick a funnel at the top of seat tube sealed up nicely with some caulking to try and keep the foaming lye off the frame.
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Old 12-31-13, 10:37 PM   #14
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I took a frame with a stuck post to a diesel truck shop on a Friday afternoon.....I'd never been there before, but this is the old civil south.....

"A friend of mine said you guys could probably get this out, but I don't know....." 20 minutes later, after applying something vile from a spray can and employing a vise as big as an outboard motor; the stuck post was out....

You need more vise in your life......
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Old 12-31-13, 10:43 PM   #15
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Quote:
Originally Posted by ppg677 View Post
I'm trying to salvage a Trek 613 frame, with one heck of a stuck aluminum (fluted) seatpost.

I've tried bench vise (well the best I can given that the vise wants to rotate under very high torque no matter how hard i tighten the vise).

I've tried ammonia for 30 hours.

I've tried PB Blaster.

I've heated it up the post with propane twice, my most recent effort I then stuck the hot post in the snow (its -16 Fahrenheit today) and then I immediately tried bench vise.

Seems my next options are either cutting it out with a hacksaw blade (maybe finagled to a broom stick dowel) or to dissolve it out with lye. Which option would you chose?
Here is my seatpost adventure from last fall. Cut it out sucessfully.

http://www.bikeforums.net/showthread...=#post16018389

Last edited by loky1179; 01-01-14 at 12:10 PM.
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Old 01-01-14, 09:17 AM   #16
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Originally Posted by Kopsis View Post
They lye approach is effective but can take a considerable amount of time to do it safely. When I went that route on an old SR seatpost (installed deep enough that the flutes funneled water into the top of the seat tube), a week of lye solution still only dissolved about half the wall thickness. But it was enough that going at it with a hacksaw blade after that was a much more manageable operation.

If you go the lye route, I recommend mixing the lye solution in a 1 qt Pyrex measuring cup immersed in a water bath for cooling. Dissolving pure NaOH in water releases a lot of heat, even before it comes in contact with Al. Wait until the solution is completely cool before adding it to the frame. Start with a relatively low concentration solution so you can get a feel for how much heat it's going to generate in the frame. As you replace with fresh solution (a couple times a day) you can gradually up the concentration until you hit a point where the seat tube is about 150 deg F. Higher concentrations will work faster, but you risk paint damage from the heat.

Be very careful working with the solution -- gloves, goggles, lab apron, etc. NaOH burns are no joke. Also make sure you have good ventilation and that if the seatpost lets go or the lye dissolves through it, you have something safe to catch the mess that drains out.
Just don't keep lye in the measuring cup - it dissolves glass, given enough time. Pyrex-branded kitchenware is also not generally made of pyrex glass anymore (1998 on), and can shatter from thermal shock.

The stuff bubbling out of reacting lye is hydrogen, and very very flammable. Do this someplace well ventilated and away from flame/spark/etc.

Last edited by Nerull; 01-01-14 at 09:24 AM.
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Old 01-01-14, 12:33 PM   #17
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Quote:
Originally Posted by 3alarmer View Post
I know you've already tried heat, snow, and PB Blaster, but while you still
have something to grab in a vise and twist on, get some CRC Freeze Off at
an auto parts store, heat the post one more time, with a heat gun or torch
(being mindful of the painted seat tube), and then hit the post at the insertion
point and up and down the tube slot with the Freeze Off.

You need a vise that will not slip, so before doing this, find one that will not move at all.


Otherwise, if this fails if the post is not in too deep the hacksaw method works.
(You attach a small washer to the free end so that it can ride along on the seat tube
past the post bottom and not cut into the frame tubing.)

If you can find a frame guy and talk nicely to him, you might find someone willing
to ream it out for you. I've never tried that one, myself.

The hacksaw thing is a method for the patient and methodical, and is quite laborious.
Thanks for the tip! CRC Freeze Off worked!!
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Old 01-01-14, 12:54 PM   #18
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Ummm.... Just for future reference: aluminum has a greater thermal expansion than steel.

When the two are heated, aluminum expands more than steel. And when the two are cooled, the aluminum contracts more than steel.

If you have an aluminum part stuck in a steel hole, you don't heat the whole thing because that makes it stuck even worse. You have to chill the whole thing, and the aluminum will shrink more than the steel does.
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Old 01-01-14, 02:02 PM   #19
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Ummm.... Just for future reference: aluminum has a greater thermal expansion than steel.

When the two are heated, aluminum expands more than steel. And when the two are cooled, the aluminum contracts more than steel.

If you have an aluminum part stuck in a steel hole, you don't heat the whole thing because that makes it stuck even worse. You have to chill the whole thing, and the aluminum will shrink more than the steel does.
The idea of heating the seatpost and then cooling it is an attempt to break some bonds. Moreover when you heat up both the seatpost and the seattube, the steel seattube doesn't dissipate its heat nearly as quickly as the aluminum when cooled.
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Old 01-01-14, 04:17 PM   #20
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Thanks for the tip! CRC Freeze Off worked!!

....another unsolicited testimonial from a satisfied consumer.
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Old 01-01-14, 08:32 PM   #21
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Thanks for the tip! CRC Freeze Off worked!!
Well shoot. Now I want a do over.
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