So, We have something called "Gratiferia" Here in Buenos Aires, which is a sort of garage sale, only that everything is for free. There's a facebook page where people can give away stuff, or ask for something. While I was giving away some stuff myself, A guy offered me to look at what he had. So I gave him an ice-cream making machine, and he gave me a ugly rusted bathroom scale that always stuck on 10 Kg. What a Sucker! I ripped him off! hahaha!
I went to work right away!
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Step 1: Disassemble, Diagnose
So this is how it looked when I got it. the plastic fell off due to rust, and the insides were full of dust and rust.
To pull it apart, I unhooked two springs that pull the top and the bottom together. two of the lever arms got stuck to the top, but it didn't matter because I was going to take everything apart anyway.
I found that It got stuck just because the dial wheel was bent and scraped against the mechanism. I bent it back easily, as it's just a flimsy metal sheet.
At this point, I sprayed every moving part with WD40 and went to the internet to look for "how an analog bathroom scale works"
Step 2: Disassemble Entirely, and Rinse Everything
After Learning how everything worked and went together, I disassembled the whole thing. I Didn't take pictures , but it's fairly simple: Remove the nut holding the dial disc, then the disk and it's little base. After that, remove the spring that pulls the dial back to 0, and the two short lever arms. The hardest part is to remove the zeroing wheel entirely from the bolt. The bolt was pressed out of shape to lock the wheel in place, so I pressed it back with pliers, and twisted the wheel off carefully so I wouldn't damage the threads. After this, the main spring assembly and arms should come off. the rest of the frame was welded/riveted to the base and couldn't be removed.
After that, I Rinsed everything with hot water and a toothbrush. I used soap on all exterior pieces too.
Step 3: Remove the Old Paint
Using a metal sponge first and a grinder with wire brush after, I removed all the old paint and most of the Rust.
Step 4: Paint!
I rubbed everything with thinner, and masked the mechanism. then I applied a coat of primer on everything. After that, I applied 3 coats of mate black on the bottom. The white paint can I thought I had was depleted, so I put 2 more coats of primer on the top. Later I remembered I had some transparent paint, and I applied that.
Step 5: Remove Rust From Al the Little Parts.
While I waited for the paint to dry, I soaked all the mechanism parts in de-oxidizer. I also wiped the "lens" with polishing paste to get rid of the cloudyness.
Step 6: Put It Back Together
After the paint dries, and the pieces are all de-oxidized, clean and dry, you can put it all back together, just like it came off, but backwards :P
Be sure to add a little WD40 or some similar product to all moving parts, to lubricate and protect them.
I glued the plastic back on with contact cement. The plastic face snaps on.
Step 7: Before and After Comparison
Just a few before/after pics.
I hope you found this useful, or at least entertaining. goodbye! :)