Plated parts

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Huib
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Joined: 17 Dec 2008, 10:12

Re: Plated parts

Unread post by Huib »

Compliments, Luca.

Very good job indeed.
piggdekk
Posts: 47
Joined: 19 Sep 2020, 12:07

Re: Plated parts

Unread post by piggdekk »

Thank You Huib.
It's a tedious job, and as for all plating/painting processes cleaness makes all the difference on the result. Removing blueing from the fine threads is the hardest part, and You can't really spread the process over days because once blueing (or old rust) is removed flash rusting starts nearly immediately. Once bolts are ready the process goes quite fast, still with my set up (power supply, plating volume) I cannot plate more than 6-8 M8 bolts at the time, and 4-6 M10, at least if I want the plating to be uniform.
Next batch will be the disc and caliper bolts. Disc bolts need to have the unthreaded part to keep the disc from moving, but they are not DIN 931 standard size so I had to source longer ones and cut them to the correct lenght. As for the caliper bolts I will clean them up (they still show some of the original copper plating) and replate. They are machined and I have no idea if I could source them new, I'm lucky the original ones were copper plated and held so well for nearly 60 years.
luca
piggdekk
Posts: 47
Joined: 19 Sep 2020, 12:07

Re: Plated parts

Unread post by piggdekk »

ah, and as far as zin plating is concerned, the plating You get today is, thankfully, based on chromium trivalent and not chromium esavalent like in the good old days. The latter is more resistant but far more toxic and it is no longer allowed.
As far as restoration is concerned tri-valent gets the job done, but if look is not that important I would use more modern and environmental friendly methods.
luca
Huib
Site Admin
Posts: 1778
Joined: 17 Dec 2008, 10:12

Re: Plated parts

Unread post by Huib »

Over the last year we have occasionally tried to do zinc plating ourselves. So far without succes.

About the brake calliper bolts.
Both the small 1/4 UNF bolts for the cylinders as well as the bigger bolts to fasten the callipers to swivel / axel are stronger than the standard 8.8 for metric bolts.

Equivalent to 10.9 is all right I think.

Note that the unthreaded part for the big bolts is inch size.
The front is 1/2 inch. The rear is 7/16 (I am not sure. Please check). The thread though is metric fine.

I buy UNF bolts. Cut them to length and use an M12x1.25 resp M10x1.25 thread cutter on the thread. Fortunately the pitches are close enough for it to work.
piggdekk
Posts: 47
Joined: 19 Sep 2020, 12:07

Re: Plated parts

Unread post by piggdekk »

I figured out by myself that Zinc plating is quite tricky, no matter what youtubers say.
I also had mix successes, but preparation is key as well as overall cleaness. Doing it only form time to time makes it more challenging and I believe with a well built set up (with filters and agitation) one stands far better chance of success.
I used it on the calipers, that I first cleaned with electrolisys. Electrolitic cleaning is fantastic and works every single time:
Calip1.jpg
Calip4.jpeg
calip5.jpg
Cleaning by electrolysis is great because it only removes rust, no iron is removed by the process.

Next is plating:
870942.jpg
the issues here are that plating may become dull for multiple reasons (electrolyte cleaness, high current, lack of brightner...), and it doesn't reach as well areas that are shielded. I'm planning to build a set up that keeps the parts moving all the time so that there are more chances for the zinc to distribute evenly.

At last the chromate layer:
870943.jpg
While it sonds as simple as dipping the parts in the chromate, the reality is that it is not. PArts need to be thoroughly cleaned before they can be put in the chromate, then they need to dry for a few hours and it's much better done at fairly high temperature. I use a dryer until all droplets are dried and then leave them in the sun. If You touch them, or move them, or wet them during the first 8 hours or so the chromate reaction will not occurr and the zinc will be exposed.

In a nutshel what I learned is that what people charge for plating isn't enough to making it right, and that even then results may not be perfect because we are dealing with old parts with inevitable surface damage. I try not to use it on bolts because I don't want to risk H2 enbrittlement if bolts can be sourced anyway.
luca
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