Unusual Starrett 0-6" Micrometer

electron2002 · May 23, 2016

I came across a very unusual Starrett Micrometer this weekend, the likes of which I have never seen before. It is an adjustable 0-6" Micrometer, with adjustment achieved by siding the micrometer head down the body, indexing it using a pin and locking it with the thumb screw. There is no model number on the micrometer. There are four patent dates listed. The oldest 5/28/1889 would refer to patent #404057, which is a patent specific to the design of this micrometer. The other patents appear to be general patents regarding micrometers. The newest patent is 4/17/1900, so it can't be any older than that.

I can't find any reference to it in any old catalogs that I have found. The DATAMP results for patent 404057, shows another photo of one of these, but it appears to be missing the clamping shoe for the thumb screw.

Monarchist · May 24, 2016

electron2002 said:
I came across a very unusual Starrett Micrometer this weekend, the likes of which I have never seen before. It is an adjustable 0-6" Micrometer, with adjustment achieved by siding the micrometer head down the body, indexing it using a pin and locking it with the thumb screw. There is no model number on the micrometer.

Disadvantage for trying to use it on round stock at full extension.

Advantage in that it needs less space to use or store than the large, intrusive 'Cee' frame of a swappable anvil mic.

'Guess' is an industry specific niche need. Railroad or steam powerplant goods, perhaps. And/or an inspector or millwright who had to travel with limited tools he could carry on public transport. 'Light' it would not be. Compact, yes. Sort-of. But very rugged as payback for the extra weight.

JM2CW

Bill

opscimc · May 24, 2016

electron2002 said:
I came across a very unusual Starrett Micrometer this weekend,...

Are there pins in the sliding mechanism that drop into place in those holes in the "handle" to position it at 2", 3", etc.?

electron2002 · May 28, 2016

opscimc said:
Are there pins in the sliding mechanism that drop into place in those holes in the "handle" to position it at 2", 3", etc.?

There is only a single pin and you have to manually insert it in the proper combination for each of the 6 sizes. There are 6 holes in the fixed beam and six holes in the sliding portion for the 1,2,3,4,5&6" positions. But at least on this one, they neglected to actually mark which two holes need to align for each of those settings. It's pretty easy to figure it out though

awander · May 28, 2016

It's a No. 128 "Patent Six Inch Mocrometer:

From p. 73 in Catalog 17:

awander · May 28, 2016

Can you see any reason why they needed the six holes in the sliding jaw, and the staggered holes in the beam?

I have wondered why they didn't just use 6 holes in the beam, in a straight line, and a single hole in the sliding jaw.

oldster · May 28, 2016

To prevent "rocking" around the single pin. Otherwise, it would have had to had extremely tight sliding fit.

Lee (the saw guy)

Mike Nash · May 28, 2016

I would think it was to prevent errors due to re-machining through an existing hole 5 more times.

awander · May 28, 2016

oldster said:
To prevent "rocking" around the single pin. Otherwise, it would have had to had extremely tight sliding fit.

Lee (the saw guy)

Hi Lee:

I'm having trouble envisioning what you mean. It still only uses a single pin, even though it has lots of holes.

awander · May 28, 2016

Mike Nash said:
I would think it was to prevent errors due to re-machining through an existing hole 5 more times.

Do you think that's how it was manufactured? Assembled, set to a specific position, and then the holes drilled,reamed, and bushed at the same time?

Mike Nash · May 28, 2016

awander said:
Do you think that's how it was manufactured? Assembled, set to a specific position, and then the holes drilled,reamed, and bushed at the same time?

I am only certain that I don't know. It was what came to mind based on the description in the catalog page you posted and the fact that it was around 100 years ago.

Bruce Nelson · May 28, 2016

awander said:
Hi Lee:

I'm having trouble envisioning what you mean. It still only uses a single pin, even though it has lots of holes.

Lee has it right. Two locating pins are to prevent it from rocking around the axis of a single pin.

awander · May 28, 2016

Mike Nash said:
I am only certain that I don't know. It was what came to mind based on the description in the catalog page you posted and the fact that it was around 100 years ago.

It's certainly possible.

awander · May 28, 2016

Bruce Nelson said:
Lee has it right. Two locating pins are to prevent it from rocking around the axis of a single pin.

Well, I'd agree with you both, except for the fact that the tool only uses one pin.

The photos don't clearly show that, but the page I posted from the Starrett catalog surely does. (edited: "does" was "do")

Incidentally, the patent dates are all right around the turn of century, and the tool no longer appears in my 1938 Starrett catalog, so it looks like it wasn't manufactured for too many years.

awander · May 28, 2016

The May28, 1889 Patent was US Pat No 404057, Patentee Morris F. Smith of New Haven CT.

The patent text is interesting, and I encourage you to look it up. The current link is:

Patent Images

though, of course, this may change, but looking it up by the date and Patentee name should always be possible.

The patent shows that there is a gib that takes up any slop or rocking motion of the jaw, and also that there is only one pin, so Lee and Bruce, i am afraid you got it wrong, though it was certainly a very plausible theory.

The patent also claims as it;s main point, the fact that the manufacture takes place by making the holes while the tool is set using a gage block, so Mike, your first thought appears to have gotten it correct.

awander · May 28, 2016

In any case it is a cool tool!

electron2002, can we get some more photos?

The real Leigh · May 28, 2016

awander said:
The patent text is interesting, and I encourage you to look it up. The current link is:
Patent Images
though, of course, this may change, but looking it up by the date and Patentee name should always be possible.

The simplest free patent retriever I know of is www.pat2pdf.org
It provides these for free, while www.pat2pdf.COM charges a fee.

Enter the patent number 0404057. The leading zero is required.

- Leigh

Phrost9977 · Apr 8, 2022

I just got one of these

Mine only has the May 28 1889 pat. Date...

michiganbuck · Apr 8, 2022

I think that is very cool, never saw one like that.

Dieseltech870 · Jan 24, 2023

electron2002 said:
I came across a very unusual Starrett Micrometer this weekend, the likes of which I have never seen before. It is an adjustable 0-6" Micrometer, with adjustment achieved by siding the micrometer head down the body, indexing it using a pin and locking it with the thumb screw. There is no model number on the micrometer. There are four patent dates listed. The oldest 5/28/1889 would refer to patent #404057, which is a patent specific to the design of this micrometer. The other patents appear to be general patents regarding micrometers. The newest patent is 4/17/1900, so it can't be any older than that.

I can't find any reference to it in any old catalogs that I have found. The DATAMP results for patent 404057, shows another photo of one of these, but it appears to be missing the clamping shoe for the thumb screw.

Is there anyway I could bug you for the specs and a couple pictures of the locator pin. Just picked one up and that was missing. Also is the jam screw 8x32?

Unusual Starrett 0-6" Micrometer

Plastic

Diamond

Stainless

Plastic

Stainless

Stainless

Hot Rolled

Aluminum

Stainless

Stainless

Aluminum

Stainless

Stainless

Stainless

Stainless

Stainless

Diamond

Plastic

Diamond

Plastic

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