A warning on pipe-cutters

Hacksaw FTW!?! I tried using a pipe cutter once (it was about as sharp
as a marble mind you), and it just spiralled up the
seatpost.

Why would they close the bottom of the seat post? I recon it's to keep
your stash in


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dunno Ken, sounds awfully unlucky or something else is going on.

I have two KH36 frames here, and a bunch of seat posts all cut using a
small pipe cutter. Zero problems with seat posts getting stuck. No force
required to insert them, just some grease. Sorry I know that doesn't
help you much!

You are cutting your KH36 frames down right, don't know if anyone else
is doing that. Is there a chance that is part of what is going on?

As soon as you say (even limited) force is required to fit a seat post
straight away I'm thinking trouble. Given the nature of things it's not
surprising posts don't come out if they required even a relatively small
amount of force to go in.

I've lost track of which seat posts you are using too. How about trying
the new KH posts... next time?


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Thanks Mal,

I'm using a Schlumpf aluminium seatpost. The other one that got stuck
was a Cromoly Schlumpf seatpost.

It is definitely not me cutting down the seat-tube that's causing the
problem. It's quite loose up the top. It seems to taper down as you go
further down the seatube...it's get's snugglier, but I never forced it!

Every bike shop I've been to advises against using pipe-cutters. Many
of them have a special hacksaw guide that they use to cut down seatposts
with, and also a funky little orange juicer like tool used to clean up
the tube afterwards.

I managed to get the seatpost out today, with a bit of bashing it came
out.

I also did what Gerblefranklin suggested and laid it on the flat
surface. You can see there is a gap between the post and the table. Not
a huge amount, but enough to wedge it in there. You can see in the
photo how much I've filed off the ends, yet it makes no difference
because the taper/flare affects the whole tube.

Throw away the pipe cutter and get a hacksaw guide. It'll save you
alot of heartache and trouble. It's actually just as quick to cut down
your post.


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gerblefranklin;1169577 wrote:
This is silly. Really. Next time, before you insert the seatpost, put it
on a flat table an look at it. You will easily be able to tell if it's
flared. If it is, file it until it is not.



I just did that. See my photo above. It's been pretty well filed, but
the pipe cutter has actually warped the whole tube, so you'd have to
file down the entire tube to get rid of the flare.


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GizmoDuck;1169703 wrote:
Throw away the pipe cutter and get a hacksaw guide. It'll save you alot
of heartache and trouble. It's actually just as quick to cut down your
post.

Next thing you will throw away your unicycle and get a bike! You don't
have to listen to everything a bike mechanic tells you. Pipe cutters
work very well on aluminium seatposts despite Ken's struggles.

GizmoDuck;1169704 wrote:
the pipe cutter has actually warped the whole tube, so you'd have to
file down the entire tube to get rid of the flare.

It did not! The pipe cutter does not have enough force to warp the
entire tube. It cuts the end off and pushes a small amount of material
up near the edge, which is easily filed or sanded off. It looks to me
like your seatpost was already warped, or was warped by too much
pressure in the seat clamp in your last frame perhaps. With the amount
you struggle using simple hand tools Dr Ken, I wouldn't want to have you
operating on me!


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GizmoDuck;1169703 wrote:

Throw away the pipe cutter and get a hacksaw guide. It'll save you
alot of heartache and trouble. It's actually just as quick to cut down
your post.



There is nothing wrong with using a pipe cutter to trim a seat post,
provided the pipe cutter is an appropriate size and it's used correctly.
A hacksaw or whatever else works for people is ok too. Just cut the
thing with whatever, clean it up sufficiently and get riding


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Ken - looking at the pictures on the t7 thread, it looks like the
problem might be less pipe cutters, but more because you're short, and
you're cutting the seatpost too long. Just cut your seatpost a bit
shorter, so it doesn't go right down to the bottom of the seat tube, and
you should be okay.

Or at least that's the case if KH36s are the same as KH frames always
used to be, with the seat tube being not quite as long as it looks from
the outside, as on the inside there is some reinforcement on the bottom
bit, meaning you have to cut the post shorter. Pashleys used to be the
same, and I had exactly the same problem once when I rode home with a
broken seat clamp - the seatpost sticks into the reinforced bit, and it
can really get solidly stuck.

Joe


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For the record, I believe bike shops recommend against using pipe
cutters because seatposts such as the thomson with non-round insides can
be damaged and poorly cutoff with the use of a pipe cutter. I do not
believe it is related to any percieved ability of the pipe cutter to
damage the post more than a hacksaw (ever accidentally raked a hacksaw
blade along the part? I know I have).

Ken,
That was not the distortion I was expecting to see, but it's certainly
not good. I think that could be part of the cause of your problems,
since the bending of the entire tube makes it seem as if it has a larger
diameter than it does. In this case, filing, or other material removal
methods are not the solution. I would place the seatpost on a press
between a pair of v-blocks and straighten it. I was suggesting filing in
the case where the post is flared. And I hate to criticize you (really),
but unless there is something terribly wrong with your technique, the
pipe cutter should not be causing the distortion pictured. It is also
possible your seattube tapers at the bottom, but I would want a
machinist (not a bike mechanic) to inspect it in person to be sure of
that. As for how it got stuck with out undergoing significant force or
chemical or thermal bonding somewhere, you got me.

For the record, I do work at a machine shop where we have, on occasion,
done bike parts. I have cut quite a few seatposts (among other things),
with tools ranging from lathes, hacksaws, bandsaws, angle grinders,
milling machines, and yes, pipe cutters. I personally used a pipe cutter
for all of my own seatposts until mine fell into disrepair. Then I lost
it.

So now, when I'm desperate, I use a hacksaw and a file for deburring.
Or, if I am less desperate, I use a hacksaw, and then square up the base
on a faceplate sander or belt sander (not like the one used you your
table). When I am doing a permanent shortening, I prefer to do the
cutoff operation on my lathe, which is far more precise than necessary,
but I do enjoy the results. The cutoff operation, if done incorrectly,
can leave similar results to that of using a dull pipe cutter, however
with a lathe, removal of the plastically deformed metal is easy-just
take a skim cut or use a file (while the lathe is running) to remove it

gerblefranklin;1169724 wrote:
For the record, I believe bike shops recommend against using pipe
cutters because seatposts such as the thomson with non-round insides can
be damaged and poorly cutoff with the use of a pipe cutter. I do not
believe it is related to any percieved ability of the pipe cutter to
damage the post more than a hacksaw (ever accidentally raked a hacksaw
blade along the part? I know I have).

Ken,
That was not the distortion I was expecting to see, but it's certainly
not good. I think that could be part of the cause of your problems,
since the bending of the entire tube makes it seem as if it has a larger
diameter than it does. In this case, filing, or other material removal
methods are not the solution. I would place the seatpost on a press
between a pair of v-blocks and straighten it. I was suggesting filing in
the case where the post is flared. And I hate to criticize you (really),
but unless there is something terribly wrong with your technique, the
pipe cutter should not be causing the distortion pictured. It is also
possible your seattube tapers at the bottom, but I would want a
machinist (not a bike mechanic) to inspect it in person to be sure of
that. As for how it got stuck with out undergoing significant force or
chemical or thermal bonding somewhere, you got me.

For the record, I do work at a machine shop where we have, on occasion,
done bike parts. I have cut quite a few seatposts (among other things),
with tools ranging from lathes, hacksaws, bandsaws, angle grinders,
milling machines, and yes, pipe cutters. I personally used a pipe cutter
for all of my own seatposts until mine fell into disrepair. Then I lost
it.

So now, when I'm desperate, I use a hacksaw and a file for deburring.
Or, if I am less desperate, I use a hacksaw, and then square up the base
on a faceplate sander or belt sander (not like the one used you your
table). When I am doing a permanent shortening, I prefer to do the
cutoff operation on my lathe, which is far more precise than necessary,
but I do enjoy the results. The cutoff operation, if done incorrectly,
can leave similar results to that of using a dull pipe cutter, however
with a lathe, removal of the plastically deformed metal is easy-just
take a skim cut or use a file (while the lathe is running) to remove it
.

I would rank the preferable tools (when properly used) as follows
(note, I am assuming you have a suitable half-round file to deburr with
later):

1. Bandsaw with miter guage. For aluminum, a woodcutting bandsaw with a
10-14tpi blade on its slowest (or only) speed will work. For any other
material (except if you somehow have a magnesium post), you need a
bandsaw which can be slowed down to metal-cutting speeds.

2. Lathe, with partoff tool.

3. Pipe cutter.

4. Bandsaw without miter guage.

5. Hacksaw with vise.

6. Hacksaw with unicycle frame.

7. Angle grinder.

8. File alone (yes, it can be done, with enough time).

I rate the angle grinder so low because many angle grinder cutoff
wheels are not meant to run aluminum, and it is dangerous and bad for
the wheel to cut aluminum with it. Inexperienced users (such as those
who would find a list like this useful) also tend to overheat the base
metal, which is not good for steels.

I rate the pipe cutter below the bandsaw with miter guage because the
pipe cutter is slower, and leaves more of a mark on the post than the
bandsaw. Still, a pipe cutter is damn good at what it does.

A hacksaw with a file for deburring is by far the most versatile,
cheap, and effective. A hacksaw and file will cut pretty muh any
material every used for a seatpost, including the "mighty" titanium. You
don't need a jig. The base of the post doesn't need to be square
(nobody's ever gonna see it). Just get it close, and go hit the trails.

And remember, you are of course allowed to disagree with me. If pipe
cutters make your life hell, don't use them. Just remember, even if
others can make it work, if you can't, just do something else (or get in
person help from an "expert", whomever that may be.

Ugh, an essay. I hope it saves someone some trouble though.



Hey Mr Gerble,

Thanks for the detailed answer. And I love that it's followed by your
sig line "just ride"

Anyway, I won't be using a pipe cutter again. I didn't have the
problem when I used a hacksaw and the bike shops hacksaw guide.

The post that got stuck yesterday was cut by someone else...so I don't
know what sort of pipe cutter they used. My last post before that was
cut with a pipe cutter also, but the one I used had a really big wheel.
So maybe that made it flare out even more.

I don't have an angle grinder handy...but of course if you do, then why
would you faff around with a hacksaw or pipe cutter?

The bike shop told me they don't use pipe cutters because of the
flaring....I remember my mechanic wrestling with a bike frame and
seatpost clamped in a vice not that long ago (and cursing the customer
who brought it in). Not sure of the reason it got stuck but they hate
removing stuck seatposts

Ken


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At least not if the world was full of rusted muffler clamps, pipes in
places an arms length away with no room for a hack saw, or anything that
****es me off by existing somewhere I don't want it to. Why bother with
pipe cutters, hack saws etc. ? 50 ish dollars and you have a saws all.
It will not only cut a seat post effortlessly in seconds, but anything
else in your life that needs to go. Don't waste the rest of your life
without one of these.


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