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Polishing stainless steel

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Polishing stainless steel

Old 03-11-23, 03:07 PM
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smontanaro 
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Polishing stainless steel

I need to finish polishing the stainless steel dropouts on my frame. The fronts were done quite awhile ago and came out pretty well. The rears required more work pre-brazing and have some deeper scratches. I'm struggling a bit to get rid of them. I'm familiar with khatfull's aluminum polishing thread. Aluminum is a piece of cake. Still, the steady progression from coarser to finer grits should be the same, right? My files are generally 0 and 1 coarseness (not sure exactly what the numbers mean other than larger numbers being finer is there any correlation between that an the numbers used to indicate sandpaper grit?). The sandpaper I have on-hand goes 80, 120, 220, emery cloth, 600. (Just by feel, my guess is the emery cloth is finer than the 220, but coarser than the 600.) I think my problem is the jump from the #1 file to the 80 grit paper might be a bit large to pull off. I think I might need a finer file or coarser sandpaper. Right now I've stopped with the files and am cycling through the sandpaper, then proceed to the polishing wheel (green stick on Dremel polishing bits). I'm still left with some scratches from the filing. I'm not sure the 80 grit is coarse enough to remove the scratches left by the #1 file. Should I just keep cycling or look for something intermediate between my finest file and coarsest sandpaper?

Here's a quick pic. I'm not too worried about the finer scratches all over the dropout. I'll eventually take care of them with some of the finer sandpaper. The couple deeper scratches near the chainstay are the bigger issue.

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Old 03-11-23, 03:28 PM
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Hate to say it but them's some deep scratches. The key to polishing SS dropouts is don't use such a coarse file on them in the first place.

Now that you have the file marks, there's nothing you can do but sand down the entire surface down to the depth of the deepest gouges. Or just live with 'em. Oh I guess you could fill them with silver to have less steel to remove but I'd only do that with gouges even deeper than yours. Another heat cycle is best avoided unless necessary.

Even 80 grit is kinda coarse for something that you're going to polish later. But given how much metal you need to take off, it may be unavoidable. You might want to use something with some "inhuman" power, like a sanding drum in a die-grinder. I have a Dynafile, but that's a big expensive tool most hobbyists won't have.

The big huge ginormous problem with power tools is that it's so easy to take too much off somewhere, and it can happen too quickly for you to notice and correct before it's kinda deep. I'd much rather see some file marks than evidence someone went too far with power tools. So the safest way is to just sand it down, with elbow grease and patience.

Do you know about cross-sanding, to reveal the existing scratches, especially each time you switch to a finer grit. You have to get ALL the scratches out before moving to the finer grit. Cross-sanding will show you when you're ready to go up a grit. Yes 600 grit could theoretically take out 40-grit scratches, if you live long enough, but don't do that to yourself..

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Old 03-11-23, 04:41 PM
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There are relatively inexpensive band filers available at harbor freight. I'm not sure how to even start with a band filer on that dropout though.

Like Mark says, you have to start at approximately the grit that caused those scratches. When I polished a lot I would sand at +/- 45 degrees and 0 and 90 degrees. That breaks up the scratches into diamonds. Then go to the next finer grit and so on. What you are doing is making progressively smaller peaks. I used automotive finish sandpaper and diamond paste. One time I took a piece of aluminum down to .1 micron which is less than the wavelength of visible light. Since my microscope required glancing light all the light bounced off and none of it went into the microscope. I wasted most of a day trying to figure out what I had done wrong. Thought I had broken the microscope. That was the last time I went below a micron.

A swirling pattern is generally counterproductive.
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Old 03-11-23, 05:16 PM
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More oriented towards wood and maybe obvious/intuitive enough, but I found this (and many of his videos) very informative.

- graph above comes up about 4min into video


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Old 03-12-23, 09:29 AM
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Agree with what everyone else has said, unfortunately your going to have to start with something pretty abrasive to get those scratches out then start moving through the various stages of sandpaper making sure you have successfully sanded out the previous scratches you just made. Something worth noting, since I assume the frame is finished and you won't be adding any washers to the dropout for the QR to grab onto, is that polished surfaces are do not make for the best non-slip surface for skewers to grab onto. This is less of an issue for vertical dropouts such as these but worth noting.
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Old 03-12-23, 10:38 AM
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Thanks for the feedback. As this is my frame for me, it's not like I have to achieve perfection for a customer. I'll do what I can, but not get too carried away with it.

The ideal situation would have been to add washers. They came with the rear dropouts but not the front. When I asked the supplier about it they said the fronts and rears came from two different suppliers (which I thought a bit odd, but oh well). I could, in theory, search McMaster-Carr for suitable washers for the front, install them, then paint the non-washer-covered parts of the dropouts. I'll give that some thought as well. (The frame hasn't been painted yet.)

8aaron8 mentioned that polished stainless steel isn't the best grip surface for skewers. How is that different than chrome plated dropouts? I have a few bikes with plated ends (and horizontal dropouts), and have never had grip issues. Is stainless steel that much harder or slicker than chrome plated steel?
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Old 03-12-23, 10:50 AM
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What dropouts are they? I guess they aren't from Coast. Too bad Paragon stopped making that style dropout.

I think for vertical dropouts grip should be fine. With chrome and horizontal dropouts, grip can be a problem. I rode my bike with chrome horizontal dropouts off of my trainer twice before I switched to a stronger skewer. Then I ruined the bearings in the trainer because they weren't meant for strong skewers. Probably in the process of ruining another bearing, but haven't had the opportunity to switch bikes.

I designed some washers for front dropouts but never had them cut, a little over a buck apiece. I never found a washer I wanted on McMaster. I forget why I wanted them actually.
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Old 03-12-23, 01:36 PM
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I think "polish" is an unfortunate choice of words trying to describe an acceptable or appropriate finish. I recommend a "brushed" finish with the last stage being created with 80 or 100 grit emery. A rear wheel will leave marks as soon as it is is clamped tight on a shinny surface wrecking all the polishing work. The dropouts are not in highly visible locations and they will be mostly covered up with the QR skewers anyway.

The file numbers Skip is referring to reference the coarseness on Swiss Pattern files. Just like sandpaper you start with course files (like a #00 or #0) to create the shape and then use finer files (#1 or #2) to get rid of file marks. In Skip's case the fine tooth file he is missing is a #2. By the way there are inconsistencies in Swiss Pattern file numbers. How course are the teeth is based on the size of the files as well as different brands have a different coarseness for the same file #.

At this point what I would recommend is using a combination of Swiss Pattern #1 and then #2 files to get rid of the bulk of the scratches until the surface is prepared enough to polish with emery cloth. And when I say "polish" I don't mean making the surface glossy smooth, I mean just making all the scratches look consistent.
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Old 03-12-23, 01:50 PM
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Originally Posted by unterhausen View Post
What dropouts are they?
955N (rear) and 959 (front) from Ceeway.
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Old 03-12-23, 05:12 PM
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As mentioned above a lot of older frames with chromed dropouts also suffer from rear wheel slip, I think a good skewer can go a long way to alleviate this issue. You're likely fine with what you have since they are vertical and not horizontal dropouts.
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Old 03-13-23, 09:37 AM
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Originally Posted by Doug Fattic View Post
I think "polish" is an unfortunate choice of words trying to describe an acceptable or appropriate finish.
While polished might well have not been the finish I should have gone for that is what I was after. <wink> I do like shiny. In my case, I felt there were two choices, shiny or painted. I really don't like how badly paint gets chewed up by skewers. Chrome plating isn't really an option. (It is, but I'd like to avoid the environmental consequences.) A "satin" or "brushed" finish hadn't occurred to me.

It is frustrating that the Ceeway fork ends didn't come with washers. Looking around, I found some this morning I believe I could adapt, both on McMaster-Carr and boltdepot.com. I suspect they are identical parts. Either would require some thinning, which might be a bit challenging.

I'll hunt around for a #2 file. I did find a Nicholson triangular file in my modest collection which seems finer than my 0's and 1's, but it's not marked numerically. Instead it reads "DBL.EX SLIM." According to the pics for it on Amazon, it's an American Pattern file. (I saw a review on Amazon which read, "Works well sharpening my saws." I'm sure that's all my dad ever used it for.

Not sure if the Swiss matters. Since it has no safe edge, I'll have to be careful to always stroke away from the margin at the chainstay. If that doesn't seem to work well, I'll just go buy a Swiss #2.
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Old 03-13-23, 11:54 AM
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You should be able to put a safe edge on a file. Particularly easy with a bench grinder. It might be doable with a dremel
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Old 03-13-23, 12:34 PM
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Originally Posted by unterhausen View Post
You should be able to put a safe edge on a file. Particularly easy with a bench grinder. It might be doable with a dremel
Maybe more straightforward with a rectangular file (mine's triangular)?
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Old 03-13-23, 12:45 PM
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there are triangular files with safe edges, you just have to smooth the vertex. I am familiar with those from making guitars.
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