I usually cut down my seatposts for the unicycles...being short tends to require me to do this quite often.
Usually I use a hacksaw and special guides that clamp on to the seatpost. That what my bike shop recommends. Their advice being...if you use a pipe cutter, be prepared to have the thing warp or flare out on you. Never use a pipe cutter to chop down a post.
Well, I got lazy and did just that today. After cutting my Cromo seat-post with a pipe cutter I filed it down. And then stuck it into my brand new KH36" frame.
It went in fine.
It doesn't come out.
It's completely lodged itself inthere. And the more I wiggle it, the tighter it gets.
I will try to remove it with a vice tomorrow. If not, then it's consigned to the scrap heap
I've seen people use pipe cutters many times, but be careful. Filing it doesn't necessarily correct the defect.
Rob . Northcott 26 September 2008 16:14:06 [ permanent link ]
..but it's really easy to cut a seatpost with a hacksaw... takes about a minute, or possibly two if you include the filing time, and hanging the saw up afterwards. What's the problem?
Anyway, I hope you manage to get it out OK Ken. You must be able to extract it with a vice without damaging the frame even if you have to sacrifice the seatpost. If you give up and decide to scrap the frame, send it to me
Tomkarches 26 September 2008 16:16:07 [ permanent link ]
I've also had a (aluminum) seat post get stuck after cutting. It took two people tugging at it to get it loose.
If you use a pipe cutter, make sure that any flaring is totally filed down. I did not have this problem with cutting a steel seatpost with a pipecutter, most likely because steel is less prone to flaring.
Angle grinders are relatively inexpensive and should leave a cleaner (no flare) cut. Be sure to wear safety glasses.....tom
Don't give up yet. If you are getting discouraged, take it toa bike shop, they deal with these problems every day.
If you are really wanting to give it a go, consider the different properties of the metal. An aluminum tube will expand with heat faster than a steel tube, so start by heating the seat post tube with a hair dryer or a heat gun (be careful). See if you can get some antisieze lubricant down the tube, even a little will help, so drip it on, then start wiggling.
I use a pipe cutter for my seat posts now. It does cause a little bit at the end flare out, but i spend about 5 minutes using a file to get rid of that little lip and then I grease it up and see how it goes in the frame, if it is too hard to get in then I file it some more. I have had no issues.
Hopefully you can get it out without damaging your KH 36
Fine for steel or cromo posts but grinders dont work so well on non
feris metals. The disks kind of clog and dont cut as well.
It's worked perfectly well on steel and aluminium posts; it goes through the latter like butter. The only type left is carbon, and I'm (a) not likely to ever have one or (b) want to cut it with a normal hacksaw either!
Peleschramm 26 September 2008 19:10:53 [ permanent link ]
I always use a pipe cutter...
That must be why my current post is so hard to put in and pull out of my frame (the new kh post/frame)...
I'll have to give filing a go. I remember last time I took the seat out it took like 20 minutes hopping sif and pulling up on the seat, wiggling it back and forth.
Saskatchewanian 26 September 2008 19:44:48 [ permanent link ]
I use a pipe cutter and have noticed a very slight flaring on the Cro-Mo posts that I use. I have had no problems with a bit of filing but have never used an aluminum post.
uhh i have had this problem, but from the frame warping at the bottom and/or bending ... never the seatpost... i never had a problem w/ my steel frames unless there was a little rust or something... that said, last time i got my seatpost out of my DX it took a 3' long 2x4 and a curb.
Isaac Steiner 26 September 2008 20:37:47 [ permanent link ]
When I got my KH36. I was down at Bedfords picking it up, and when he was trimming the post for me, he used a pipe cutter, and it was very hard to get into the stem, actually we couldn't get it to. But once we got some grease around the post it slipped in and out really nice.
If your going to use a pipe cutter, I recommend grease (not just some little spray lubricant, kinda like a gel, i'm not sure exactly what it's called)
Peleschramm 26 September 2008 20:41:20 [ permanent link ]
isaac steiner;1103336 wrote:
When I got my KH36. I was down at Bedfords picking it up, and when he
was trimming the post for me, he used a pipe cutter, and it was very
hard to get into the stem, actually we couldn't get it to. But once we
got some grease around the post it slipped in and out really nice.
If your going to use a pipe cutter, I recommend grease (not just some
little spray lubricant, kinda like a gel, i'm not sure exactly what it's
called)
That's my advice,
Isaac
Has worked in the past for me.
Only problem is you have to remember that the post is all greasy every time you take it out so that you don't stain your clothes. You're still bound to stain your hands. I may have to try that or file down my post now.
Pedrotejada 26 September 2008 20:47:49 [ permanent link ]
I had the same problem with my KH Alum SeatPost!
At UNICON I used Lars pipe-cutter... Me and Miles cutted, but it got stucked... We used a little but of water and roated the seatpost a lot...
Be aware! Maybe you scratched your seat tube, and maybe you have little aluminium pieces between the seatpost and the seat tube... Remove the seat tube and clean it!
Here when I arrived I used Kitchen Soap and worked fine... Anyway, my seatpost do not looks good... For my luck I use it all the way down!
I think you might be onto something Ken (and others). You've got me wondering if I'll ever be able to get the seatpost out of my KH36 again. I had trouble getting the seatpost into the frame following KH seatpost amputation via a pipe cutter. After much filing in went in without grease. I hope it'll come out.
i think the problem is ppl getting overly tight with the pipecutter,
just don't crank the cutter so much.
That is what my Dad told me (after I got a seat post stuck in a frame). He said if you cut too fast it'll flare the end a lot more, but even if you do crank it really slowly, filing the outside edge is not usually a bad idea.
It took us an afternoon to get the seat post out of my KH 36 frame after I got it lodged in there. In the process of trying to separate the two pieces, I scratched up the inside of the frame so much that I couldn't get the post back in even when it was filed. We had to use a round file and a few invented power drill attachments to smooth the inside of the frame again.
Lesson learned: don't be so impatient with the pipe cutter, and file the edge of the seat post.
Lesson learned: don't be so impatient with the pipe cutter, and file the
edge of the seat post.
This has been what's worked for me. I haven't cut too many posts with the pipe cutter, but so far no problems noticed. You have to file if you use a hacksaw anyway, but I don't think you need to file as much if you make a gentle cut with the pipe cutter. All pipe cutters may not be created equal however, so some may be more flare-prone than others...
We used a little but of water and roated the seatpost a lot... Here
when I arrived I used Kitchen Soap and worked fine... Anyway, my
seatpost do not looks good... For my luck I use it all the way down!
You're doing it wrong!
Soap and water are for washing your hands, not for working with metal.
Unless it's oil or grease, you shouldn't be putting it on a seatpost... you're only going to make things worse.
Really, you can use any oil on your seatpost in a pinch... even motor oil or vegetable oil... just remember to wipe off any excess to keep things clean.
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For the record, I did file the post after using the pipe cutter. Quite a lot of filing in fact, but obviously not enough.
The pipe cutter causes the bottom to flare outwards due to the pressure from the pipe cutter roller. So it means you can get it into the frame easily enough, but when you try to pull it out, it's like a rachet- it cuts into the seatube and stops you from pulling up.
It's almost welded itself into the frame now. I'm going to take it to the bike shop to use a vice and a blowtorch.
I use a small plumbing pipe cutter (made for cutting copper pipe) and take it easy, low pressure, no rush. Then give the cut a quick sandpaper just to take the sharp edge off, bit of grease, job done.
Ouch! I never thought about the possibility of the seatpost getting
stuck because of using a pipe cutter to cut it.
I have always used a pipe cutter. Gives an even cut. The one thing I
do when using a pipe cutter is to make sure that the roller is on the
side that I want to keep. That way most of the mushrooming happens on
the side of the pipe that I'm going to throw away. I still need to file
some, just not as much.
Good warning though. I'll have to rethink my preference for using a
pipe cutter rather than a hack saw.
I'm not sure what you mean. The pipe cutter was an industrial one with rollers on both sides.
We spent an hour wrestling with the frame, and heating it up with a paint stripper. We moved it about 2cm, and then gave up.
I'm getting another KH frame. The alternative was to take it to an engineering workshop to see if they can drill out the seatpost, but the problem is that I don't have the time to faff around with that, and also, by the time they charge for labour etc, it probably would just be easier to buy a new one.
I've had a bad day :mad:
Ken
p/s if anyone doubts the strength of the KH frame, I can vouch for the welds. We gripped the top of the seatpost in a vice, and basically bashed the $@#! out of the frame for over an hour. We also torqued the fork arms with a very large piece of wood, and wrestled with them until my knuckles turned white.
No sign of any cracks in the welds, or bent fork arms as far as I can tell.
We spent an hour wrestling with the frame, and heating it up with a
paint stripper. We moved it about 2cm, and then gave up.
I wouldn't give up on that frame just yet. Is this one of the frames that allows you access to the seatpost through the bottom of the fork crown? If not, cut the seatpost off the frame, leaving approximately 1" sticking out (for purchase to pull on, later). Then take a raw hacksaw blade and go at the seat post from the interior, cutting a slot in it from the inside outward. If you're patient, you can do this with very minimal damage to the frame. Once the slot is through the seatpost, when you tug on it the circumference will collapse into the blade slot you made and it should come out. If you can access the post through the fork crown, I would concentrate only on the bottom inch or so, since we presume that is where the binding is.
If you do get it out, I'd carefully inspect the frame for any burrs or similar damage that might stick the *next* seatpost. They can easily be cleaned up with a ream, or even a rat-tail file.
I wouldn't give up on that frame just yet. Is this one of the frames
that allows you access to the seatpost through the bottom of the fork
crown? If not, cut the seatpost off the frame, leaving approximately 1"
sticking out (for purchase to pull on, later). Then take a raw hacksaw
blade and go at the seat post from the interior, cutting a slot in it
from the inside outward. If you're patient, you can do this with very
minimal damage to the frame. Once the slot is through the seatpost, when
you tug on it the circumference will collapse into the blade slot you
made and it should come out. If you can access the post through the fork
crown, I would concentrate only on the bottom inch or so, since we
presume that is where the binding is.
If you do get it out, I'd carefully inspect the frame for any burrs or
similar damage that might stick the *next* seatpost. They can easily be
cleaned up with a ream, or even a rat-tail file.
No, it's a frame that is sealed at the bottom.
I don't normally give up easily, but I'm also not silly. Spending several hours on something to just save a few dollars is not worth it. I have no attachment to the frame...because it's new. If it was my Coker frame then that's a different matter altogether. That has sentimental value, and I'd happily file it down with sandpaper before I gave up on it.
It really is depends on whether there are any KH frames in stock.
Ken how large was the pipe cutter you were using? From what you say re filing, it sounds like it was too big for the job causing excessive flaring of the metal. The pipe cutter I use can only handle up to 30mm dia, with a narrow cutting wheel - see pic. Haven't had any problems, no need for filing, just a light sand.
Not that it helps much now, but didn't it feel unusually tight when you started to put the seat post in?
1.) Bring it to me. I'll get it out in no time and then we can go out for Thai food. No charge.
2.) Tri-nitro-toluene
3.) Sheldon Brown's hacksaw blade technique. Hacksaw blades in a frame have the teeth oriented to cut on the forward stroke. When using a blade that is not in a hacksaw frame, reverse the teeth so the cut is in the pull direction. Otherwise the blade is like a noodle during the cut stroke. Hold the section of hacksaw blade with vice grips or a c-clamp. Use plenty of light oil or WD-40 to lift the slurry as you cut.
Here is an idea that I have used before successfully. It is a little involved, but not too bad. You will need the following:
1. Four ~1' pieces of 2x4 2. ~3' of Braided metal cable 3. Cable clamp 4. Drill 5. car jack
Build a square frame using the 4 pieces of 2x4s. Drill a hole in the middle of one side big enough for the seat post to fit through. Drill a hole through the seat post near the top of the post. Push the seat post through the hole in the wood frame so that the top of the seat post is in the center of the square frame. Take the metal cable and thread it through the drilled hole in the seat post. Make a loop with the cable over the board directly above the top of the seat post (use a cable clamp to close the loop). Take the jack and place the base on the 2x4 above the top the seat post and loop the cable over the top of the jack. Crank the jack. Either the seat post will pull lose, the frame will bend, or the 2x4 will break, but something is going to give.
Here is an idea that I have used before successfully. It is a little
involved, but not too bad. You will need the following:
1. Four ~1' pieces of 2x4
2. ~3' of Braided metal cable
3. Cable clamp
4. Drill
5. car jack
Build a square frame using the 4 pieces of 2x4s. Drill a hole in the
middle of one side big enough for the seat post to fit through. Drill a
hole through the seat post near the top of the post. Push the seat post
through the hole in the wood frame so that the top of the seat post is
in the center of the square frame. Take the metal cable and thread it
through the drilled hole in the seat post. Make a loop with the cable
over the board directly above the top of the seat post (use a cable
clamp to close the loop). Take the jack and place the base on the 2x4
above the top the seat post and loop the cable over the top of the jack.
Crank the jack. Either the seat post will pull lose, the frame will
bend, or the 2x4 will break, but something is going to give.
THAT is SO COOL. And simple. The car jack could even be replaced with a crude fulcrum and lever. The hole in the 2x4 could be big enough for the seat post tube to fit through. Then you're pushing on the crown.
Mikepenton 27 September 2008 19:45:44 [ permanent link ]
Maybe you could weld something to the top of the seatpost to give you more leverage for rotating on that end...? (disclaimer - I know nothing about welding) Better to get a new seatpost than a new frame, or both. Good luck!
Very interesting thread. I've used a regular hacksaw and file all these years. I save the ends for some funny reason. You should see how many I have! This year, I received the great gift of a pipe cutter (thanks John!) and have used it so far one or two times with no problem. It's a smallish one though and I cut slowly.
Sounds like getting that saw guide from Performance would be the way. Save the pipe cutter for actual pipes.
Ken, that's a drag about your uni. I have one that's similar. It's a 29er that I rode on a trip in 2005. We rode through salt water on one day and I've never been able to remove the seatpost since. Good luck with yours.
You guys are doing this the hard way. What I did was I just grew till I was exactly 6 feet tall. When I got my KH24, I stuck the seat post in the frame till it bottomed out. I then sat on the uni and it was the perfect height, no need to cut anything. Same thing when I got my KH20 and my coker. So I suggest you guys need to drink more milk;)
after 22 seconds of vigorous sawing through the guide, you will have a straight cut with no flaring. then, you file the outside edge with a file -or a quick twist at a grinder. finally, you score the inner edge with a deburring tool to remove any razor sharp burrs.
the deburring tool is more important if you use a cut wheel on a power tool, where burrs become more frequent inside the post , (and inside your eyes)... don't forget the noise factor either. If you want a straight cut -and -the light show... use a chop saw! Oh, remove flammable substances from the area in which you are using cut wheels -trust me!
pipe cutters don't tend to flare steel as much as aluminum, and if you go slower with lighter pressure -you lessen the flare, but will still need the use of a grinder -and it takes longer!
It's possible some metal grit or a burr is also preventing the removal of the post from your frame. PB blast is good stuff to spray in there (hours) before you clamp the post in a vice. Also, when you twist, figure out how to hold onto the crown instead of the frame legs or wheel -the aluminum frame won't un-twist nicely.
If that fails, and you haven't trashed the frame, lop off the post at the top of the frame. get something called a "jab" hacksaw, and cut the post from the inside out -toward the frame along the length of the post. You will need to make 3 cuts (120 degrees apart) or 4 cuts (90 degrees apart) and then wedge a screw driver between the seat tube of the frame and the segmented post and tap the post bits away from the frame where they can be removed.
It's time consuming, but you can still watch unicycling videos or meditate while you work, and unless you are getting paid $100 hr -it's worth your time to fix an expensive frame.
Take the frame to a bike shop, where they will re-condition the inner surface of the seat tube with a flex hone, or a reamer which are expensive tools that are used far too infrequently to own yourself (hopefully).
A fast arm with a hacksaw can get through a seatpost in about 1-2 mins, depending on how concerned you are with perpendicular cuts. This leaves no flaring, and any burrs that occur can be filed off quite quickly, so I'd definitely vote for a hacksaw.
But if you do happen to have your uni's seatpost stuck, I'd sit down on the floor with your legs straight out on the crown or pedals. Then twist and pull the seat with all your might. The one time I got mine stuck, I did it this way and it came out alright.
Another way I can think of is taking the car jack from your car and supporting it with wood on the crown until it touches the seat. Then jack it up and it should pop out the seat.
A fast arm with a hacksaw can get through a seatpost in about 1-2 mins,
depending on how concerned you are with perpendicular cuts. This leaves
no flaring, and any burrs that occur can be filed off quite quickly, so
I'd definitely vote for a hacksaw.
But if you do happen to have your uni's seatpost stuck, I'd sit down on
the floor with your legs straight out on the crown or pedals. Then
twist and pull the seat with all your might. The one time I got mine
stuck, I did it this way and it came out alright.
Another way I can think of is taking the car jack from your car and
supporting it with wood on the crown until it touches the seat. Then
jack it up and it should pop out the seat.
Edit: Nathan, I save the ends too. Weird.
Thanks to everyone for all the suggestions.
I can assure you we were pretty brutal in our attempts to get it out.
It would probably have snapped any other frame in half.
The next step is either to cut down the seatpost, make another slot, and possibly use a smaller diameter seatpost, or else get an engineer to drill it out. Both of these will take considerable time and/or expense.
TonyMelton 29 September 2008 05:20:16 [ permanent link ]
I've used a pipecutter to cut down many seatposts, both steel and aluminium, without problems. As John Childs pointed out, when you use a pipecutter one of the freshly cut ends will flare out more than the other. You want the flared end to be on the excess seatpost you're removing. I've actually marked my pipecutter with the letters 'XS' on one side of it to remind me which way it goes. My other 2c on pipecutters is that you want to rotate them so that the blade is trailing rather than leading. This prevents spiralling.
TonyMelton 29 September 2008 06:23:51 [ permanent link ]
That towel on the ground (removed for photographic effect) was protecting the uni from rock-related damage. Successfully, too. I prefer mounting cranks with shoes rather than rocks, these days. Shoes without feet in them work best.
If you are worried about flaring, cut the seat post about a centimetre too long, using a pipe cutter. Then cut off about a centimetre with a hacksaw. Hey presto! You have removed the flared bit.
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