Micrometer Question

this little micrometer came into our possession along with some other engineering stuff, it has an unknown history

It seems quite accurate in comparison to other ones that we have. However part "A" does not move separately from art"B" and there is no torque release (normally you can only tighten a micrometer to a certain tightness, as I'm sure you will all know)

Not sure what the screw spring assembly does on the end.

I feel the whole thing is jammed, some release oil has not helped - so before I start to use some real effort to turn "A" with respect to 'B'. Has anyone got any suggestions or knowledge of this micrometer, and how best to proceed - I don't want to make things worse

Edited By Justin Thyme on 03/01/2023 21:04:44

YouTube 221 this may help

Mike

The 221 stamped on it is the Starrett model number

Google 'Starrett 221 instructions' and follow some of the links.

You will find:

https://3dwarehouse.sketchup.com/model/ue7fb53b1-e9e8-4935-977a-5c87a7156b2d/Starrett-221-micrometer?hl=en

which leads to:

https://worldwide.espacenet.com/patent/search/family/023454424/publication/US2267332A?q=pn%3DUS2267332A

and there is a Hollywood movie of it as well:

https://www.youtube.com/watch?v=vM_pBlk4J_s

Aside from being a Starrett … which is a good start … it’s a 221 … which is even better.

Treat it gently: You may get some ideas from this

.

That's clever!

Rob

Looks like we all gravitated to the same place !!

It must be Lust …

MichaelG.

Edited By Michael Gilligan on 03/01/2023 21:52:47

I want one..............I certainly dont need one, but I want one

At $799, I thought about it for a moment, but fortunately they seem to be discontinued.
https://www.starrett.com/metrology/product-detail/T221XL

Bill

When i saw this thread I thought i had one. But it is different & not Starrett. It is a Moore & wright ModelDR961.

I think it works the same though. Anyone know.

Steve.

Steve,

I think you would find it is a geared system. I have the metric version.

K

thanks for the replies but they don't really address my problem. Part 'A' in my picture (Coarse Thimble Assembly) does not move in relation to Part 'B' ( Fine Thimble Assembly)

This is potentially a nice little tool and I don't want to start trying to force anything with vices, pliers and hammers. Not even sure if I should be trying to get a bit of thin oil between the stuck bit.

I know this is clutching at straws but is the anvil locked on the knurled screw on the u part . Sorry if a stupid Q&A

Whatever you do don't use force of any kind! Too lovely of an instrument to be ruined by that.

First thing I would focus on would be that locking ring mechanism. There is usually a tapered sleeve or similar in there than that can jam up if left in the locked position for eons. I would try WD40 in there and work it gently back and forth. Everyone has their favourite releasing fluid, but I find WD40 contains a good solvent that gets rid of most gummed up oil etc, and it lubricates as well, which some releasing fluids don't.

Otherwise I would stand it upright and try drizzling a bit of WD40 etc down the sleeve for a few days, and see if that helps. If not, complete submersion in something similar might be in order. If that does not work, find someone with an ultrasound tank and put it in there for a bit. Gunsmiths and instrument shops often have such tanks.

Maybe try emailing Starrett in the USA? Or try one of the websites for forums for Starrett collectors.

Edited By Hopper on 03/01/2023 23:46:39

Edited By Hopper on 03/01/2023 23:48:24

Here Here. good idea Hopper. Plus gas is superb at releasing stuck parts. Readily available in the UK.

Steve

And if all that fails, on most micrometers, if you take that little spring-loading tensioner device off the end,the thimble is mounted on the exposed spindle by a taper. So if you carefully hold the thimble and tap the end of the spindle downwards onto a block of hard wood etc on the bench, the thimble should come loose on the taper and come off.

You can then inspect the thimble and try to work out how to get the two parts apart, or at least have better access for your releasing fluid.

Would be best to read some material/watch some videos on micrometer disassembly in general first so you have a bit of a roadmap.

There were two patents mentioned in the video

MichaelG.

I have found boiling stuff in oil a good way of freeing stuff up, but may keep that tactic until later. Will dry a few days of wd40 type stuff, I also have a contact at a staretts factory, I may email her.

anyway, may be to clarify where it is not stuck, this is it dismantlement as far as I can

Ah, ok, so it's the actual interface between the one thou main thimble and the tenths of a thou secondary thimble. Which would have to be some kind of friction drive so that when you turn the main knurled area on the tenths thimble, it turns the thou thimble, which must be hard mounted to the spindle in some way.

A drawing of how that is done would be muy helpful. Perhaps MG's suggested patent application drawing? No idea on how to look that up. Ask MG.

One of the patents has already been kindly mentioned by DC31k …

but for ease of reference: **LINK**

https://worldwide.espacenet.com/patent/search?q=pn%3DUS2267332A

The other one should be easy enough to find, by searching Espacenet on the claimant’s name

[ presumably either Hagstrom or Starrett ] … it only gets brief mention in the video.

MichaelG.

Edited By Michael Gilligan on 04/01/2023 07:31:18