Classic & Vintage - Polishing a seatpost
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I got a fluted seatpost for my Le Tour III in the impossible-to-find (anything cool) size of 25.8 and I want to shine it up all shiny. It's got that machining texture to it so I'm hoping I can get pay someone else to do it. Problem is here in LA all the machine shop sort of places are clustered pretty far away from me, so I was wondering if there's anywhere else I might try taking it.
For instance- maybe a jeweler could do it. Or maybe... I dunno, I'm just wondering if some type of business does this sort of thing and I'm just not aware of it. Like one of you might say "yeah, bagel makers usually have a polishing machine, ask one of them" except not as ridiculous.
07-06-07, 05:50 PM
You might try asking your neighbors or coworkers if they have a polishing wheel. Chances are that if you ask enough people, one of them will have one.
07-06-07, 05:57 PM
Do you have a power drill? All you need is a mount, a polishing wheel and some polishing compound. I usually use a dremel type tool with a polishing head, but it takes a while because of the size.
Just know that if you are going to DIY, it is not too difficult. Just make sure that you set an optimum speed - not so slow that nothing happens, and not so fast that the compound/wheel burns.
07-06-07, 06:00 PM
A buffing wheel won't do it if you're starting with a machine finished post. You neet to smooth out the grooves first. I use a 1/4 sheet pad sander and medium fine paper. I smooth the scratches from the sander with steel wool and then I buff it on a cotton wheel with rouge. You can do the same thing by hand, it just takes a lot longer. Figure out how far you are going to insert the post and don't sand below that point. I cover the part I don't want to sand with duct tape.
07-06-07, 08:54 PM
I totally lost track of this thread. Thanks for the info.
07-10-07, 05:15 PM
What comes to mind when polishing out machine marks is, the diameter of your seat post will be reduced around .006" or more, that may pose a problem.
None the less this is how I would do it. Start with 150 grt emory cloth with a slight twisting motion and reversing the directon of sanding that will leave a cross hatch patern" this will help maintain roundness" work your way to 300grt emory paper. Next, use wet/ dry 600 grt with a penetrating oil [WD 40] Finally use Mothers metal polish on a flannel cloth. It would take me about an hour doing it by hand.
Here is an example of metal polishing I do on a more difficult surface, a motorcycle heads combustion chamber. Using the cross sanding method, no bumps or lumps.
07-10-07, 05:57 PM
I've polished some seatposts by hand to a mirror finish this way:
1) Mount the seatpost without saddle in the frame, about 5 mm higher than it will be when finished. Place a big rubber or plastic washer over the seatpost to protect the frame.
2) Cut long strips of wet or dry sandpaper and put one round the seatpost, support the rear wheel with your knees and work the sandpaper back and forth, evenly. Avoid staying in one place, cover all surface. I started with #320 and continued with #600 grit sandpaper. Continue until the machining marks are gone.
3) Cut rag strips about 30 cm long and work in the same way as before, with polishing paste. I used water to 'thin' it.
4) Same as #3 but with auto polishing compound.
5) Same as #4 but with clean rag.
Note: The seatposts I polished were solid round, possibly with a fluted one you have to be extra careful so as to keep the fluting edges sharp.
Well I just did diminishing sandpaper, and then mother's, and it turned out "good enough". It's got a lot of weird gouges and stuff so I didn't knock myself out trying to make it a mirror, it's just nicely shiny. I thought it would take a lot more work than it did, just a couple hours, really.
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