-holiday76

Has anyone ever sanded down a seatpost ? I've heard of people doing this with stems so why not a seat post? I have a 3t 27.2mm seat post that I'd love to use on my Gios which seems to take a 27.0 seat post. It's fluted, but I think that the flutes won't be inside the frame so that part shouldnt be an issue.

Grand Bois

I've sanded down and then repolished a couple.

-holiday76

did you use a grinding wheel to do the sanding part? How do you keep it from going out of round? Or does it even matter?

RobE30

Damn, I was hoping that you had a 27.0 seat post floating around. I need one for the Mondia

mazdaspeed

I'm also interested in hearing what the best way to do this is.

rothenfield1

I was wondering about this too. I recently used fine sand paper on the light superficial scratches with so-so results. But the deep gouges would require aggressive sanding or grinding. On the same topic, sort of, some old frames have a massive amount of gunk built-up in the seat tube that causes even a new post to stick, which requires twisting to remove. What method, if any, do you use to clean the seat tube. I hope I'm not distracting your thread holiday76.

DRietz

I was going to have Khatfull do one for me, but I got busy and never replied to him. Rude, I know. We love you, Keith!

We had decided the best way would be to find something that fit inside the seatpost to mount it on a drill. That way, you could just apply pressure with some emery cloth and get 'er down.

If anybody finds something that fits inside a seatpost relatively well, let me know. Or, if anyone in the Bay Area has a lathe, mounting on one of those would work too.

To Rothenfield1: the best way to clean the seat tube is to ream it.

Otis

The best way to change the size would be to cut it on a lathe. But if sanding is your only option. Make a clamping block by boring a 1" hole in a small chunk of 2" x 4" then split it down the middle. Then you can use both halves to clamp the post in a vise or to a bench top with a c-clamp. Cut strips of wet-dry sandpaper about an 1" wide along the long side of the sheet. Sand using a "shoe-shine" motion using soap and water in a spray bottle as lubricant. Keep turning the post in quarters as you go to keep everything even.

For polishing I would start with 220 or finer depending on the amount of scratches, then work up to 1000 before buffing. To knock .2 mm off you might want to start with 80. Just make sure you are diligent about removing the scratches between each grit as 80 will leave some nasty marks. It helps to wash the post in water between each grit so you can see that the scratches are being erased and you do not co-mingle the grits.

DRietz

Otis - do you know of anything that would fit or expand into a seatpost's inner diameter?

Otis

Hard not to give a smart-ass response to that...........But:

I do not know of anything offhand but if you looked through enough wood and metal working catalogs I'm sure there's something that would work. An adjustable reamer could probably be used, if you had a drill press with a large enough chuck to hold it. There's adjustable rubber arbors that hold sandpaper rolls that may come in a size that would work? You could probably just use a wood dowel with a slight taper and a wood/metal thread stud centered in one end to use to chuck it.

It might be hard to get something to keep the post turning true as you apply pressure. once it's turning off-center your going to be screwed. A drill press is not a lathe.

buldogge

I either turn the post down on a lathe, or I just take a ball hone to the seat tube. We're talking .004" here!

AngelGendy

I recently took a 27.2 down to 27.0 with a belt sander just turned it slowly and checked it often it worked well.

Glennfordx4

I use a small dia drum sander with a drill bit extender to clean inside of seat post ( note if you have a braze on's for a water bottle remove them 1st) tubes. I just used it to clean up the seat tube on my Schwinn Crosscut which had destroyed a SR TCO post when I removed it from so much crud & corrosion that built up on the inside.

Glenn

rootboy 

A tough nut to crack in a precision way. There is a tool designed to hold the inside diameter of a tube on a lathe or, drill press. It's called an expanding chuck. I have a couple but both larger than the ID of a seat post, and, they're designed to hold one end of the tube while the other end is supported on a tailstock center. Not an option on a seat post. An expanding, rubber sanding drum probably won't work as most of them are designed to be tightened with a nut on the outboard side of the drum, the part that would be buried inside the seat post. You might be able to make something but the trouble might be more than it's worth. Held in a metal lathe, the portion held in the chuck is the same portion you need to turn down, making that method difficult. Even with all the tools and machines I have available, I believe I'd revert to the hand-held sandpaper method if I were attempting this. A seat post is not as critical to keep perfectly cylindrical as a stem would be, of course.

Edit: I spoke too soon. just went down and looked at my expanding sanding drums and two of them indeed tighten with a nut on the inboard, or shank side of the drum, making this a viable option if you can find one of the right diameter. Held in a drill press, the other end of the post, the clamp casting area, would still need to be supported and I think I would use Otis' split block method, clamped to the drill press table and perhaps lined with some felt to avoid scratching the post up near its top. This might work and would give you a level of precision greater than hand-held sandpaper.

rhm

Someone whose math skills are more advanced than mine (this would include just about everyone) might want to check me on this, but:

I would take a flat file and cut a series facets 3 mm wide onto the surface of the seat post; there would be room for around 30 facets. Each facet should meet the neighboring ones at the surface of the 27.2 post, forming a series of 30 ridges. Then I'd file each ridge down, resulting in around 60 facets, each around 1.5 mm wide. Then I'd file all those ridges away, aiming for a round shape. Then I'd put the file down and do the shoeshine thing with wet 320 grit sandpaper, followed by 600 grit, 1000 grit, and finally polish. I think that would result in a 27.0 post....

bennie222

I have a 27.0 post I could be talked out of for you guys in search of one... It came off of this bike, its an SR Laparade style with black accents. It's not terribly long though, you're probably looking at the max height in the pic. I had a 27.0 Thomson post I've been carrying around for 10 years that I put on it so I can convince myself that it was useful to hold onto the thing for that long. PM me with an offer. Cheers.

miamijim

I use a piece of 80 grit sand paper and rotate the post and paper combo. When it gets close I switch over to 220 to reduce grit lines and then 600.

Adjustable reamers can purchased at Harbor Freight if one is so inclined to open up a seat tube.

-holiday76

i may take you up on that if my sanding fails.

canopus 

Probably the best way is is go to Advance Auto Parts or Sears and get a flexible Wheel cylinder hone, use that with some oil and a drill, quickly and gently. It doesn't take a lot to clean up a seat post tube. They make hones with three adjustable stones but I think whose will tend to remove to much material and will probably get chipped/stuck in the seat post slot cutting.

mudboy

Tomorrow, either come over and I'll give you the Dura Ace 27.0 I have, or PM me with your address and a time and I'll bring it over.

pruckelshaus AT yahoo dot com

-holiday76

I'll be in touch, but just in case you wondered, I actually need two, which is why I'm still screwing with this other one too

-holiday76

did some minor sanding with 80 and then 150 grit because that's what I had. The post goes in a little better, but I was afraid to push it any further than this.





pay no attention to the bike part explosion.

So I guess a bit more sanding and we'll be good here.

Grand Bois

A grinding wheel to remove .1 mm of aluminum? I hope you're kidding!

Some emery paper is all that is needed. I don't use anything too coarse because I sand the full length of the post and have to polish out any scratches that I create with finer paper. You can keep it as round as it needs to be by turning it in your hand. It's not a precision fit.

mudboy

Gotcha. I also have a benchmount belt/disc sander that I use for framebuilding. You're welcome to use that if you'd like.

Pete

RobbieTunes

I used a B&D workmate and an orbital sander. I slowly rotated it. I used a piece of masking tape to mark the insertion, so I wouldn't have to clean up a lot of sanded post. Started with 80, then some finer stuff, ended with 0000. Then I steel-wooled it with chrome polish and the post looks fine.

Of course, I can't hear a thing now.