Micrometer Question

[HopperParticipant @hopper]

Yes it would be much better to release it by soaking than by disassembly. It looks rather delicate inside and might take specialist knowledge to get it back together and working right.

If all else fails, carburettor cleaner spray is a very aggressive degumming fluid.

[DC31kParticipant @dc31k]

Posted by Michael Gilligan on 04/01/2023 11:29:11:

…I would guess that the problem might simply be congealed lubricant between those two surfaces…

Would there be any utility in leaving the micrometer in warm place to assist this to uncongeal (e.g. airing cupboard, 40 degree oven, quick blow dry with the Dyson Supersonic)?

[HopperParticipant @hopper]

Looking at the drawing further, I would say that those left hand sections of the coarse and fine thimbles with the narrow band of knurling are not in fact locking rings, but are used to calibrate the numbered dials to 0 when the anvil faces are together. So scratch the idea of trying to see if they are a locking ring that can be rotated. All that wil ldo is throw the reading out of calibration! Stick with the microscopists' experience of gummed oil locking their focussing thingies up and continue soaking with degumming fluid/s of choice. The suggestion of heat might help too. A bit of gentle warming can't hurt. Hair dryers work well.

[john halfpennyParticipant @johnhalfpenny52803]

Do not trust patent drawings. They may show the exact product, but since patent specifications are prepared at a very early stage and typically do not change, the drawings will not reflect developments and production engineering. I have written enough to know.

[Grindstone CowboyParticipant @grindstonecowboy]

I certainly wouldn't be brave enough to take it apart. If you have access to an ultrasonic cleaner, I'd go for that, with a suitable solvent.

Or lighter fluid usually works quite well, and leaves a very slightly oily residue.

Rob

[Justin ThymeParticipant @justinthyme24678]

had it soaked in watch cleaning stuff overnight – no joy

how about isopropyl alcohol, or even petrol ?

[roy entwistleParticipant @royentwistle24699]

It's penetrating oil that it needs. for Plus Gas.

[Grindstone CowboyParticipant @grindstonecowboy]

Petrol in preference to IPA, I would think, much better at dissolving goo (usual safety advice applies). Never had much joy with IPA.

But if you can get it, Plus Gas is excellent, or as I mentioned (if you have any) good old lighter fluid.

Rob

Edit – the above assuming it's congealed oil, rather than corrosion that's the issue.

Edited By Grindstone Cowboy on 04/01/2023 16:50:55

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Justin Thyme on 04/01/2023 14:26:39:

had it soaked in watch cleaning stuff overnight – no joy

how about isopropyl alcohol, or even petrol ?

.

How about PlusGas !!

… if you can’t find any it might help to know that it’s mostly [‘though not entirely] kerosene.

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by DC31k on 04/01/2023 12:24:16:

Posted by Michael Gilligan on 04/01/2023 11:29:11:

…I would guess that the problem might simply be congealed lubricant between those two surfaces…

Would there be any utility in leaving the micrometer in warm place to assist this to uncongeal (e.g. airing cupboard, 40 degree oven, quick blow dry with the Dyson Supersonic)?

.

Apologies for the late response … I’ve just returned from a 130mile round-trip to the Dentist

Yes … warmth often helps, although the aroma of warm Plus Gas may not please everyone.

What I have found useful on jobs like this is to avoid the temptation to dunk the lot in a bath of solvent, but rather to clean any joint lines with a toothpick, prior to applying the solvent in small quantity, locally.

Not only is it more economical, but the capillary action seems to work more efficiently.

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

For what it’s worth …

I am pretty sure this is the second Hagstrom patent relating to the Starrett 221

**LINK**

https://worldwide.espacenet.com/patent/search?q=pn%3DUS2741847A

i.e. the improvement that Starrett asked him to make

MichaelG.

.

Edit: and just to emphasise the excellent point made by  john halfpenny:

.

Edited By Michael Gilligan on 04/01/2023 20:19:18

[HopperParticipant @hopper]

I have never found alcohol, meths, rubbing alc. etc very good at dissolving anything other than the plastic lenses on instruments.

Petrol might be worth a try. It certainly dissolves much muck. And was recommended by Mitutoyo to be used to free up sticky plungers on dial indicators on an old service sheet I have. Maybe back in leaded petrol days it had a lubricating effect too? Their recommendation was just a few drops on the plunger. Cleaning the joint edges with a toothpick as MG suggests might help it get into the joint too.

[HopperParticipant @hopper]

That motion amplifying lever mechanism certainly is a fascinating one. I still can't quite get my head around how it works exactly, even after reading the description on the latest patent MG linked to. Sounds like setting it up could be very fiddly for uninitiated so best to continue with the soaking. It does look as though if you remove that screw that holds the spring loaded knob on the very end of the thimble, you could dribble a little Plus Gas or Petrol or whatever down the tiny hole the end of the spring fits into and goes all the way through, and perhaps help the cause.

Edited By Hopper on 05/01/2023 00:20:48

[Justin ThymeParticipant @justinthyme24678]

Posted by Hopper on 04/01/2023 23:40:05:

I have never found alcohol, meths, rubbing alc. etc very good at dissolving anything other than the plastic lenses on instruments.

Petrol might be worth a try. It certainly dissolves much muck. And was recommended by Mitutoyo to be used to free up sticky plungers on dial indicators on an old service sheet I have. Maybe back in leaded petrol days it had a lubricating effect too? Their recommendation was just a few drops on the plunger. Cleaning the joint edges with a toothpick as MG suggests might help it get into the joint too.

it had about 5 hours immersed in petrol to no avail. It is now wallowing in diesel and will be there for a few days as I am not about the morrow

[Phil WhitleyParticipant @philwhitley94135]

If it doesnt free up after its latest bath, try repeated warming/cooling cycles with a hot air gun, I have a lovely little Ambrose Shardlow of Sheffield ( them as forged merlin crankshafts!) 0-1/2" micrometer which was in its original box, spotlessly clean and totally seized, with repeated warming and cooling it freed off, and the cause was congealed lubricant, not a sign of corrosion. Polymerised oils make very good adhesives, but heating will free them! Good luck with it, I wish I had one, just to make ppl jealous you understand!

Phil

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