How to polish aluminium parts

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find_bruce
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How to polish aluminium parts

Postby find_bruce » Mon Aug 20, 2018 2:00 pm

There is an article on cycling tips How to polish aluminium parts. As I am currently polishing a 105 groupset, I thought it would be interesting, but it seemed a bit light on.

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P!N20
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Re: How to polish aluminium parts

Postby P!N20 » Mon Aug 20, 2018 2:23 pm

I learnt how to polish parts using John Prolly's tutorial: https://theradavist.com/2009/10/tutoria ... cle-parts/

Some things I've found over the years:
- Some parts have very stubborn anodising that needs to be sanded off rather than 'sprayed' off. A Cinelli 1A stem was particularly bothersome.
- Some parts either don't have anodising or it just comes off with the first sanding.
- Oven cleaner is lethal. Wear protective gear when using - gloves, goggles, breathing apparatus.
- Power tools make this process a whole lot easier...but I've never tried them.

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Re: How to polish aluminium parts

Postby Torana68 » Mon Aug 20, 2018 2:40 pm

A lot of this stuff the finish isn’t polished it’s the anodising. All the Shimano stuff has that nice look because of the anodised finish, polishing always looks wrong to me. What’s re anodising cost?
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Re: How to polish aluminium parts

Postby familyguy » Mon Aug 20, 2018 8:15 pm

I'll dig out the pics of the 5700 group I'm polishing up for the SCBS show next year. Having a bench grinder with a buffing wheel is good. Stripping off the original coatings without going too far seems to be the key trick.

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Re: How to polish aluminium parts

Postby uart » Mon Aug 20, 2018 8:40 pm

I'm one of those guys that always says: "No no - I like it that way. I like the patina". But the reality is that I'm just lazy. ;)

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Re: How to polish aluminium parts

Postby familyguy » Tue Aug 21, 2018 10:23 am

Here's my efforts so far:
https://photos.app.goo.gl/WdRrMthkcwjSuoLj9

The levers were masked off around the body and second paddle then wet sanded with 400, 800 and 1200, then polished with Autosol. Brakes were pulled apart completely and sat in a drain cleaner crystal and water mix for about 5 minutes. It didnt remove the 105 branding, which I think was cool. The cranks were done in the drain cleaner as well, but I left the NDS crank in a few minutes too long and it pitted a little. It's not noticeable from a few feet away but certainly is up close. I polished those on a bench grinder afterwards with Josco brown and white polishing compounds and calico buffing wheels.

All the parts need a little work before I'll be happy with them.

Still figuring out what I do with the FD and RD, can't really pull them apart much.

I did a set of 600 6200EX cranks with sandpaper along which came up OK, but having a grinder with a soft wheel makes it ten kinds of easier. Although...it does make it easier for the part to grab and get thrown violently onto the floor, or your leg. Ask me how I know 8)

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Re: How to polish aluminium parts

Postby P!N20 » Tue Aug 21, 2018 10:39 am

familyguy wrote:It didnt remove the 105 branding, which I think was cool.


That's amazing, usually the printed logos are the first thing to go.

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Re: How to polish aluminium parts

Postby familyguy » Tue Aug 21, 2018 10:54 am

I know. I had the same with the cranks but I sanded those off, even so you can see the faintest outline.

I use this stuff with some water, you can literally see the anodising cooking off as it sits: https://www.bunnings.com.au/pascoes-500 ... s_p4461111

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Re: How to polish aluminium parts

Postby find_bruce » Tue Aug 21, 2018 11:16 am

Torana68 wrote:A lot of this stuff the finish isn’t polished it’s the anodising. All the Shimano stuff has that nice look because of the anodised finish, polishing always looks wrong to me. What’s re anodising cost?

My components are 105SC which were painted "champagne" so anodising is not an issue for me - some of the bits were deeply scratched, hence heavy sanding before polishing.

The cost of anodising is mostly in the initial set-up - its been more than 10 years since I personally had anything anodised, but I understand there is a minimum cost which is currently around $100.

The better the part is polished prior to anodising, the better the result will be, however the partwill always come out less shiny after anodising - the difference is the finish is much more durable.

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Re: How to polish aluminium parts

Postby P!N20 » Tue Aug 21, 2018 11:33 am

familyguy wrote:I use this stuff with some water, you can literally see the anodising cooking off as it sits: https://www.bunnings.com.au/pascoes-500 ... s_p4461111


Interesting. I wonder if the drain cleaner is a bit 'gentler' than oven cleaner. I was recently reading a thread on another forum where oven cleaner was used to get a stuck seatpost out by eating away the aluminium!

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Re: How to polish aluminium parts

Postby familyguy » Tue Aug 21, 2018 11:43 am

Apparently the active ingredient in oven cleaner now is not as strong as the old stuff, in the interests of being more enrivonmentally responsible and all that. I've used 'green' oven cleaner that has seemingly done diddly squat. Just don't forget about aluminium in this stuff either, it will dissolve to nothing if left long enough. I did an exercise and left an old crank arm half-immersed for an hour. It almost turned into swiss cheese.

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Re: How to polish aluminium parts

Postby P!N20 » Tue Aug 21, 2018 12:02 pm

familyguy wrote:It almost turned into swiss cheese.


It's called drillium ;)

The active ingredient in oven cleaner used to be Lye. Christ that stuff is lethal.

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Keep it safe!

Postby Thoglette » Tue Aug 21, 2018 1:47 pm

familyguy wrote:It almost turned into swiss cheese.

It also produces large quantities of H2 as it does so. Keep the area ventilated :-)

P!N20 wrote:The active ingredient in oven cleaner used to be Lye. Christ that stuff is lethal.

Also see "Drain Cleaner" - straight NaOH a.k.a. caustic soda. Lye may be NaOH or KOH or other metal hydroxides but all are very caustic

Read the MSDS

Be warned that all of these will blind you very quickly - wear eye protection and have a plan to get into a shower or under a hose if you spill it on you. And stay there. If you get it in your eyes have someone call for an ambulance immediately.

Having A Plan is important - usually this includes having someone else around who knows what you are doing and knows what to do if you screw up.

Making A Plan is just the process of listing all the things you need to do (from set up to clean up); working out all the ways you can screw up (e.g. tripping over the bucket); how you can minimise the impact of said screw up (move the new car away, know where the spill will drain, wear eye protection etc); and planning what you will do in each case.
Last edited by Thoglette on Tue Aug 21, 2018 7:33 pm, edited 1 time in total.
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Re: How to polish aluminium parts

Postby find_bruce » Tue Aug 21, 2018 2:38 pm

Just in case Thoglette hasn't convinced you, a solution of NaOH at 150°C is a good way to dispose of those pesky bodies you have lying around

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Re: How to polish aluminium parts

Postby familyguy » Tue Aug 21, 2018 3:26 pm

For those playing at home, here's the Pascoes MSDS: http://www.pascoes.com.au/wp-content/up ... ls-ANZ.pdf

For those also playing at home, one teaspoon to 2 litres of water is enough to eat the ano away. Don't get it in your eyes even at that level, but skin exposure will irritate if left but will not burn. Never use it at the suggested drain cleaning ratio!

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Re: How to polish aluminium parts

Postby QuangVuong » Tue Aug 21, 2018 7:28 pm

I like to use straight caustic soda such as the Diggers stuff Bunnings has. Blasts through anodising in no time, and through stuck stems and seatposts. I do use it in very strong concentrations to speed it up though. But I do see the convenience in using a similar product out of a spray can.

Although the advice Chris gives in the article is good, it is still down to experience to get it right. To me, the two most important things with polishing a part is to maintain the shape of the original part, and also get a shiny finish without being able to see large swirl/scratch marks. It is very easy to over sand/buff a part, and this totally changes the way the part looks. I have not seen his work in real life, so it is hard to say confidently, but I still see swirls/foggyness in his finish. Take the side of this crank arm for example. Definitely could be prepared further before the polish or polished further for an even finish.
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Re: How to polish aluminium parts

Postby Torana68 » Tue Aug 21, 2018 8:02 pm

find_bruce wrote:........, I understand there is a minimum cost which is currently around $100....,,....


This any use .
http://www.caswellplating.com.au/anodizing.html
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Re: How to polish aluminium parts

Postby Roisin79 » Wed Aug 22, 2018 10:16 am

Torana68 wrote:A lot of this stuff the finish isn’t polished it’s the anodising. All the Shimano stuff has that nice look because of the anodised finish, polishing always looks wrong to me. What’s re anodising cost?

To me too, although I have always wanted to have a go at restoring my DA 7400 shifters and levers, replicating the grey-anodised finish at home.

Seems a straightforward process, something clear-anodising isn't.

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Re: How to polish aluminium parts

Postby old steel Bikes » Wed Aug 22, 2018 8:21 pm

I have now restored a number of bikes from various ages. Aluminium parts do age and oxides if not looked after or are not anodised so what I believe to be the process before undertaking any work. So what was the parts like new what is the bike going to look like when completed if I do something to one part will it make other parts look like on the bike.

Un-anodised parts will by now have started to oxidised and look worst of wear. So what did they look like when new. From what I can recall most cast parts were shinny so a good clean-up and a hand polish with a suitable abrasive one when with a liquid one should be sufficient. If this will not do the task then you can use a buffing wheel with a cutting compound. At a last resort if the oxidising has started to eat into the alloy then wet and dry paper can be used but care needs to be used as this will remove some alloy and you will lose some of the casting marks as well as some of the engraving.

Anodised parts from the late 60s to early 70s most manufactures move away for naked alloy to anodising equipment. I believed this was done to ensure their parts looked good with very little effort to clean and stop the oxidising process. So before any work to undertake removing anodising from parts whilst they look great when first done there is a lot of work to keep that look in the future. The other item is if you remove it off one part then on a bike you will more than likely need to remove it from all the other parts as well.

To me as stated before parts are only new once while alloy can be polished up again but I would not remove anodising. I have removed anodising from some parts and wish I had not. Now trying to get the parts re-anodised but the screen prints are lost for ever.

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