Author Topic: Not electronic but.....  (Read 2005 times)

SeanB

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Not electronic but.....
« on: June 28, 2016, 01:37:45 PM »
Today i decided to try something different. Had this block of solid rust that once was a nice micrometer, but which had been exposed to salt air and which was a solid block when I got it. So decided, as I had nothing to lose, to try to free it and derust it. Started by first giving a 2 hour soak in paint thinners, which got all the oil and most of the black paint off, so perfect for the next stage. Stripped it apart as far as possible, so I could do the pieces all at once.

Then it went for a swim in vinegar, and after a half hour nothing, so I decided to try electrolysis to shift the rust. Needed an anode, so used a left over carbon vacuum pump vane, as they are a service item, and i had some spares. then simply connected a 12V battery to the anode, and the micrometer as the cathode.

Bubbles, and after an hour there was a difference, so cleaned and back in again. Then again a swim and a clean, and after 2 hours finally I could see the metal on the shaft, and after some gentle persuasion with pliers it started to move in the housing.

Cleaned, washed, dunked in the thinners again then drowned in some spray oil and put the kit together, and then reset the alignment ( still not right, 3 micrometers out but fixable) and ran it a few times then oiled it again till tomorrow.


steve30

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Re: Not electronic but.....
« Reply #1 on: June 28, 2016, 06:49:56 PM »
Looks good :). Got a photo of it beforehand?

SeanB

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Re: Not electronic but.....
« Reply #2 on: June 29, 2016, 11:17:11 AM »
Sorry, I had it first with a scourer in some oil before trying this to get the rust off, then tried the solvent and only after the dunking in the electrolysis bottle that I decided to do a photo.

Spent today putting a little light oil into the mechanism, so as to get it running a lot better. Also had to replace the torque limiter, as the pin and spring that was the original limiter disappeared in the rust. So a bit of quick work with some odd stainless steel Belleville washers and a pair of scissors ( very thin washers, out of some old stuff I took apart years ago) and a little filing  and I got a torque limiter again. Still 0.03mm out, I will have to do some more alignment and do a compensation  but it is working well now.

From a solid rust block that only vaguely looked like a tool to something that moves, though I still have a lot of corrosion on the barrel and dial as that is a satin chromed item and I do not want to make too much hexavalent chrome in my work area. I did get a thin coating on the copper hanging wire after 20 seconds so decided to stop there. Chromium is good in very small amounts, and needed in your metabolism, but the dangerous dose is still a pretty low value.