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[ParkerMusselman]

Find a friend with a lathe.

edit: if unsuccessful, make a friend with a lathe.

x2: buy a lathe

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[echelon_john]

If it were me, I'd use a flap wheel on a drill to remove material and keep testing the post. No harm in going a little oversized, and it doesn't matter if it's not 100% round. Then a little black sharpie action on the lip which may show a little silver from your sanding.

If you have a dremel you can use a sanding bit on that as well.

The benefit of the flap wheel is that if you're careful it will maintain pretty good round.

Edit: This is assuming you don't have specialized tools like dedicated sanding drums/die grinder.

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[ultraman6970]

I was you and have the money I would buy an adjustable reamer, IMO is your bet choice, you put in there, 5 to 10 turns, then a litttle bit more, so on and so forth. There is no way you will screw up the clamp using a reamer.

[shovelhd]

A flap wheel might work, but reamers, machining, they will cost you more than a replacement.

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[shovelhd]

That's what I would do, and I have access to a machine shop.

[otis]

I could do it on the lathe for a small fee. PM if you want to go that route.

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[cmbicycles]

Dremel with a sanding drum would be what I would use in this case (I have it on hand though), I don't think an adjustable reamer would work well with the split in the clamp, might be prone to keep catching.
You could try to Wrap sandpaper around your seatpost, rough side out, then slide the collar on and twist back and forth until you get it down to the right size. I don't think you need have concerns about the integrity of the clamp from removing 1 mm from the lip. Should leave you with a 1 mm lip afterwards. Another thing to try would be a deburring tool, a few revolutions should take off enough material and keep it fairly round, then smooth with sandpaper, but again if you would have to go buy tools for a single use it probably isn't worth the effort.

Easiest would be just find a different collar. That would be the least involved option since it sounds like you would need to buy tools to do it yourself.

[charliedid]

Find a frame that fits the collar.

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[unterhausen]

so you just need to enlarge the lip? Half round file. 8" Bastard cut

I probably would do this on the lathe. Clamp it onto the right size tube and it would be done in a second. I have done that with seat lugs that have a lip so that f-builders can just cut the top of the seat tube off square.

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[unterhausen]

a -- it doesn't matter if it's round
b -- go slowly

[charliedid]

Good idea. I might try that, thanks. Or just wrap enough sandpaper around a 1" hole bit, which I do have here.


:D Don't tempt me, PL enabler! :D
If I found a nice Casati with those specs, I might just do it....

The collar fits the frame perfectly; it is the seatpost that is too big (29.4mm v 27.2mm).

I am custom painting both, so a 27.2mm shim is not an option.

I try to help where I can ;-)

[EricEstlund]

You have a nice bike. Quality seat clamps that fit are fairly inexpensive (Kalloy ones are what, $5-$10?). You can file on the one you have, but you'd probably be better served just swapping it out.

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[wallymann]

i do this with the aftermarket seatpin clamps i use on all my carbon colnagos.

agree that using a file will be tougher to keep round, this way it's real easy to sneak up on the larger ID to keep things perfectly round.

[EricEstlund]

Thanks- I appreciate it.

Actually, now that you mention it, I believe I have some of the Campy collars. My original post was not meant to be self serving, and I'm not sure where you are in the world, but I'd be happy to sell them reasonably as I don't use them often.

[bicycletricycle]

I have a lathe and can use it, PM me.