Mitutoyo mechanical digital micrometer mechanism stiff

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Argenti
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Mitutoyo mechanical digital micrometer mechanism stiff

Post by Argenti »

I have recently acquired a couple of these mechanical digital mitutoyo depth micrometers and have had issues with the display mechanism. When I got them they were in decent shapes and the threads in the seem to turn freely when putting the thimble back on the micrometer but when the sleeve that holds the spindle in place engages the display mechanism it seems to be a little stiff and the thimble can’t be turned with the ratchet. Upon cleaning the parts with acetone and reapplying a light oil to the mechanism it helps a little and I got one micrometer working great but the others are either stiff or have stopped engaging the display mechanism. I was wondering if anyone had any experience with these and could offer some advice on how to get these working again. I don’t have the micrometers with the electric digital readout but the ones with a plastic dial turned by gears.
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Harold_V
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Re: Mitutoyo mechanical digital micrometer mechanism stiff

Post by Harold_V »

No experience with those micrometers, but I have had a negative experience with micrometers that have been stored too long and the oil has appeared to have polymerized. Why some do and some don't remains a mystery to me, but that's the reality.

What I've learned is that once it happens, good cleaning isn't enough. The only thing that has made a significant difference is to apply a drop of ATF and allow the detergents within to break down the hardened oil. You could probably clean the parts with sodium hydroxide (lye), but that offers a little risk of removing the paint in the engravings of the typical micrometer.

This may not be addressing your problem, which may be caused by a totally different reason. I made mention only because you said that you enjoyed success by cleaning and oiling.

H
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Steggy
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Re: Mitutoyo mechanical digital micrometer mechanism stiff

Post by Steggy »

Harold_V wrote: Mon Jul 06, 2020 2:59 pmThe only thing that has made a significant difference is to apply a drop of ATF and allow the detergents within to break down the hardened oil. You could probably clean the parts with sodium hydroxide (lye), but that offers a little risk of removing the paint in the engravings of the typical micrometer.
I've gotten good results using spray carburetor cleaner (e.g., Gumout) to clean polymerized lubricant from micrometer threads. However, that's not a procedure I'd advised with a mike that has a "digital" readout.
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pete
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Re: Mitutoyo mechanical digital micrometer mechanism stiff

Post by pete »

The best product I've personally used for cleaning fine mechanisms is CRC electrical contact cleaner.It's formulated to dissolve and flush out old lubrication but still be safe around most paints and plastics. And it quickly evaporates leaving no residue behind. In general metrology equipment requires far less lubrication than most with home shops think. There very much like the lube requirements for fine mechanical watches and clocks where a tooth pick or sewing needle is used to carefully place far less than a single drop of oil and only where it's needed. Even slightly too much oil is likely more harmful to the tools repeatable accuracy than no oil at all. Excess oil creates more drag and attracts more contamination than using just enough does. The real trick is figuring out what that just enough amount is.
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