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 Post subject: Re: crank arm polishing
PostPosted: Sat Nov 17, 2018 10:48 am 
King of the Skip Monkeys
King of the Skip Monkeys

Joined: Wed Nov 07, 2007 4:34 pm
Posts: 29704
Location: in the shed
danson67 has been looking into stripping anodising.

viewtopic.php?f=1&t=391052&start=20

Oven cleaner can work but it can and often marks the aluminium.

There are various recipes on the web using phosphoric acid and chromic acid but this has to be heated and isnt really suitable for home use unless you have a good workshop:

Quote:
The composition of that bath is 80 grams of chromic acid in 3.5 liters of water, add 140 ml of 85% phosphoric acid, add water to make 4 liters. The bath is operated at 190 - 200 °F. Immerse the part for 15 minutes and then rinse well in water


other than that its a long and painful process with lots of different grades of paper and polish.


Last edited by legrandefromage on Sat Nov 17, 2018 11:01 am, edited 1 time in total.

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 Post subject: Re: crank arm polishing
PostPosted: Sat Nov 17, 2018 10:51 am 
Special Retro Guru
Special Retro Guru
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Joined: Sun Apr 29, 2007 6:22 pm
Posts: 6043
Location: burgh castle,where the pretty people live
other than that its a long and painful process ..sounds like being married...sounds like a lot of time and effort is required...


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 Post subject: Re: crank arm polishing
PostPosted: Sat Nov 17, 2018 10:54 am 
King of the Skip Monkeys
King of the Skip Monkeys

Joined: Wed Nov 07, 2007 4:34 pm
Posts: 29704
Location: in the shed
I have a set of similar period Specialized cranks and they are taking an age to remove the finish.

XT M730 cranks are anodised too so any absurdly shiny ones you meet are not original, whereas the DX were 'bare' and polish lovely.


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 Post subject: Re: crank arm polishing
PostPosted: Sat Nov 17, 2018 10:59 am 
rBoTM Winner
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Joined: Wed Jan 17, 2018 8:42 pm
Posts: 1142
Location: East Yorkshire
Most anodising firms would make a nice job. But with a minimum order charge of £250 you need quite a few bits to make it worth your while & then only if they are for keeps, not worth it if you’re pushing them on. Other option is to get a powder coating company to vapour blast then clear powder coat. But you may as well let the next custodian pay for that. Here are some bar ends I had done recently for £10


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 Post subject: Re: crank arm polishing
PostPosted: Sat Nov 17, 2018 11:04 am 
Special Retro Guru
Special Retro Guru
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Joined: Sun Apr 29, 2007 6:22 pm
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Location: burgh castle,where the pretty people live
id forgotten about having the sprayed.hmmmmm


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 Post subject: Re: crank arm polishing
PostPosted: Sat Nov 17, 2018 11:10 am 
rBoTM Winner
rBoTM Winner
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Joined: Wed Jan 17, 2018 8:42 pm
Posts: 1142
Location: East Yorkshire
gibbleking wrote:
id forgotten about having the sprayed.hmmmmm


No paint on these, that’s fine vapour blasting then clear powder coat. Much tougher than paint


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 Post subject: Re: crank arm polishing
PostPosted: Sat Nov 17, 2018 10:33 pm 
Gold Trader / MacRetro rider
Gold Trader / MacRetro rider
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Joined: Sun May 25, 2008 11:03 am
Posts: 19066
Location: Sunny Glasgow
I've found a belt sander very good for removing the grounding marks from the end of the crank.


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