removing ding in headtube?

Chris said:

My steel frame(lugged) has a very small ding in the top of the headtube, making a portion of it
slightly bent in. Will having a new race pressed in be enough to straighten it, or will it mess up
the race? I am going to be using a chorus threaded 1" headset. I'm leery of just trying to tap the
indent out, for fear of possibly causing a split in the tube, but again, maybe that would be all
it would take. Any suggestions?

Of what material is the frame? If it's steel I wouldn't hesitate to press the dent out.

When we ran a paint operation years ago, I had the opportunity to re-form the end of a head tube (
yes I dropped the frame) with a piece of pipe. If that's what you have here, slip the pipe through
the head tube and work it back and forth across the ding. You can easily press the edge round again.
(That's preferable to cutting anything)

Can't do that on a carbon frame. Titanium should respond well- like steel- in this regard.
Aluminum? No idea.
--
Andrew Muzi www.yellowjersey.org Open every day since 1 April, 1971

A Muzi <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

Chris said:

My steel frame(lugged) has a very small ding in the top of the headtube, making a portion of it
slightly bent in. Will having a new race pressed in be enough to straighten it, or will it mess
up the race? I am going to be using a chorus threaded 1" headset. I'm leery of just trying to
tap the indent out, for fear of possibly causing a split in the tube, but again, maybe that
would be all it would take. Any suggestions?

Of what material is the frame? If it's steel I wouldn't hesitate to press the dent out.

When we ran a paint operation years ago, I had the opportunity to re-form the end of a head tube (
yes I dropped the frame) with a piece of pipe. If that's what you have here, slip the pipe through
the head tube and work it back and forth across the ding. You can easily press the edge round
again. (That's preferable to cutting anything)

Can't do that on a carbon frame. Titanium should respond well- like steel- in this regard.
Aluminum? No idea.

Dear Andrew,

Do carbon frames dent? If so, why can't they be dented back out?

(There may be no stupid questions, but I am an inquisitive moron with no carbon frame experience.)

Carl Fogel

Chris said:

My steel frame(lugged) has a very small ding in the top of the headtube, making a portion of it
slightly bent in. Will having a new race pressed in be enough to straighten it, or will it mess up
the race? I am going to be using a chorus threaded 1" headset. I'm leery of just trying to tap the
indent out, for fear of possibly causing a split in the tube, but again, maybe that would be all
it would take. Any suggestions?

A tapered mandrel is the preferred means of fixing this. The lower guide cone of the Campagnolo
headset press (#733/14) works well. Don't be too aggressive, though, or you'll either flare the top
of the head tube or shatter the guide cone. Or both.

It's a good idea to re-face the head tube after this as well.

--

-John ([email hidden])

[email hidden] (Carl Fogel) wrote in message

Quoted message said:

Do carbon frames dent? If so, why can't they be dented back out?

(apologies if this has been asnwered repeatedly already)

carbon doesnt dent. it breaks. you could imagine it like a piece of glass. if you push hard enough
on it, it wont finally dimple, it just snaps. push hard enough on steel, and you will make a dimple.

this is, of course, a simplistic analogy. in truth, what is breaking is the fibers, and the epoxy
that holds them together, so you wont get a clean break like a piece of glass. carbon will also bend
a lot, compared to glass. if you put a carbon tube on two cinderblocks and pushed in the center, it
would bend, and spring back to where it started. same with steel. if you kept pressing harder and
harder, the steel would eventually permanently deform to the bend. the carbon would snap.

if you push carbon to the point at which the fibers begin breaking, there is nothign you can do to
'heal' it. you cant go in and reconnect the individual fibers that make up the structural strength
of the composite.

that is the implied danger in carbon forks, that internal fibers could break under heavy load, but
you wouldnt be able to tell by looking. if you crash your c.fork, do you know if there is internal
damage? you can crush carbon fiber pieces and hear the fibers and epoxy crackling, but stop before
the damage is complete and never be able to tell the difference (to my untrained eye). even if the
fork is plenty strong enough to hold up to normal bicycling, if something went 'crackle' inside, it
is weaker and you dont know by how much.

the good news is that the forks these days can be made so dang strong that they are rarely loaded so
heavily that damage is done. you just dont hear abotu too many forks snapping off these days, IME.

anthony

[email hidden] (ant) wrote in message
news:<[email hidden]>...

Quoted message said:

[email hidden] (Carl Fogel) wrote in message

Quoted message said:

Do carbon frames dent? If so, why can't they be dented back out?

(apologies if this has been asnwered repeatedly already)

carbon doesnt dent. it breaks. you could imagine it like a piece of glass. if you push hard
enough on it, it wont finally dimple, it just snaps. push hard enough on steel, and you will make
a dimple.

this is, of course, a simplistic analogy. in truth, what is breaking is the fibers, and the
epoxy that holds them together, so you wont get a clean break like a piece of glass. carbon will
also bend a lot, compared to glass. if you put a carbon tube on two cinderblocks and pushed in
the center, it would bend, and spring back to where it started. same with steel. if you kept
pressing harder and harder, the steel would eventually permanently deform to the bend. the
carbon would snap.

if you push carbon to the point at which the fibers begin breaking, there is nothign you can do to
'heal' it. you cant go in and reconnect the individual fibers that make up the structural strength
of the composite.

that is the implied danger in carbon forks, that internal fibers could break under heavy load, but
you wouldnt be able to tell by looking. if you crash your c.fork, do you know if there is internal
damage? you can crush carbon fiber pieces and hear the fibers and epoxy crackling, but stop before
the damage is complete and never be able to tell the difference (to my untrained eye). even if the
fork is plenty strong enough to hold up to normal bicycling, if something went 'crackle' inside,
it is weaker and you dont know by how much.

the good news is that the forks these days can be made so dang strong that they are rarely
loaded so heavily that damage is done. you just dont hear abotu too many forks snapping off
these days, IME.

anthony

Dear Anthony,

Your fiber explanation makes sense.

Given what you say, I suspect that Andrew meant that "you can't fix a dent in a carbon tube because
you can't get a dent in a carbon tube in the first place," which would have been clear to him
because he knows what he's talking about and is probably marvelling at my ignorance.

Thanks for clearing this up for me.

Carl Fogel