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Mystery micrometer

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James Dickie14/07/2021 20:42:25
13 forum posts
5 photos

I've inherited a boxed micrometer that is unlike any I've seen before. The actual head is Moore & Wright, but there is no model number visible. The head can slide along the bar and be clamped in position. The set of attachments on the right can be clamped to one end of the bar, as shown in the second picture. Those on the left all have a 3/16" pin and a 3/64" hole in the top. Their body sizes are all about 0.010" under common frctions of an inch, up to 1/2". I assume from the empty hole in the box that I'm missing an adaptor that allows them to attach to the bar. The other two rods appear to be alternative anvils for the micrometer. The clip on the shorter one matches the diameter of the bar, but there is no way to lock it in position.



I assume that this is used to measure from a bore to the edge of a component. The appropriate attachment being selected to suit and then the head being set to give a convenient measuring range, from a valve port to the edge of a cylinder head, for example.

Despite extensive searching, I've not been able to find pictures online of anything similar. This makes me think that it might be have been made for a particular job, rather than being a standard Moore & Wright product. Does anyone recognise it and shed any light on what it is?

bernard towers14/07/2021 21:06:18
401 forum posts
102 photos

The second photo looks like it could be set in tube Mike configuration.

Martin Kyte14/07/2021 21:50:56
2638 forum posts
46 photos

Looks self made to me, mic head excluded.

regards Martin

Nigel Graham 214/07/2021 22:49:46
1898 forum posts
26 photos

Possibly made for a particular range of products somewhere, by one of the tool-makers. Could even be an apprentice exercise.

I help wonder if it was originally accompanied by some form of bench-block or vice-blok that held it securely for use.

Measuring bore to edges as you suggest, including testing concentricity. Also possibly for setting between-centre boring-bars. Whatver its original purpose it looks very well-used but still capable of further service.

William S14/07/2021 23:11:10
69 forum posts
307 photos

I too have a similar micrometer, and it’s use to me is an unknown:

It looks to work on the same principle, although mine has the shaped parts in the bottom left of the box, which have threaded holes that nothing else in the box fixes/attaches to?
The rods are I think for setting the distance as they are a perfect length, the clips on yours I think is to aid setting it up,( if you have tried setting a large mic 4”+ with a setting rod one needs about 6 hands!)

like has been said above they both appear “user made” mine has been nickel plated so must of been a lull in production in the factory! or more likely done as an advanced apprentice piece

Mine came when I brought my BCA jig borer, from the widow of the previous owner who designed and made one clock in his retirement, and was a specialised welder on oil rigs for his living. Wether that leads any to any clues I have no idea.

The box on mine has been machined from a solid block of Perspex and fully polished which is more impressive almost than the actual tool!

I hope we do find out it’s purpose, it’s intriguing.


Derek Lane14/07/2021 23:34:43
630 forum posts
127 photos

My first thought was a tube wall thickness micrometer hence the round anvil for the inside circumference.

James Dickie15/07/2021 20:24:29
13 forum posts
5 photos

Thank you for all the replies. It's interesting that Williams's example has a connection to a jig borer. I know very little about such machines, but from what I've read I can imagine that these micrometers could be useful for checking features set out from hole centers.

i would hazard a guess that there's a 1950s apprentice training manual, maybe issued by the MoD, that covers the subject and suggests the construction of these tools. Certainly that environment would be more tolerant of putting as much effort into the box as the tool.

Neil Wyatt16/07/2021 00:04:06
18899 forum posts
734 photos
80 articles

They are both Tube micrometers.

More usually they are just a normal mike with a cylindrical anvil.

These appear made for inspection purposes mounted in a stand.


Speedy Builder516/07/2021 06:36:11
2502 forum posts
197 photos

A more usual form of the mike.

James Dickie16/07/2021 11:30:46
13 forum posts
5 photos

It seems like a lot of effort to go to when perfectly good tube mic's are available. As Neil says, the idea that these are for some kind of inspection whilst mounted on a stand makes sense.

interestingly, another one has just come up on eBay: Moore & Wright tube micrometer. The finish on this one looks more of a piece than the others, so it would be interesting to see if its a M&W standard product or not. Does anyone have access to old catalogues that might show something similar?

Kiwi Bloke17/07/2021 02:11:45
625 forum posts
1 photos

It's difficult to believe that these are tube micrometers, given all the additional widgets and doodads in the boxes. It doesn't appear in a 1935 M&W catalogue, but I don't think the cat included the more specialised metrology equipment. It does, however, include a common-pattern tube mic., like a standard-framed one, but with a ball-ended anvil, No. 925.

I'd suggest that the mic. is intended for direct radius, rather than diameter, measurement (or, more correctly, comparison), and eccentricity measurement, on things like gears, cam discs, lobed 'wheels' with an odd number of lobes, etc., especially if the various doodads can be put in place of the anvil (or over it?), to fit different sized bores.

Interesting bit of kit. Let's hope someone can provide an evidence-based identification.

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