Unusual Starrett micrometer

[B Halverson]

True story, I found this a number of years ago in a treacherous and overgrown garden shed behind an abandoned house not too long before the property was bulldozed by the city and turned into a parking lot. It's design surprised me because I had gone to school for tool&die in the past and had worked in a metal fab shop running some machine tools, always had some mics and calipers etc. laying around I used, but never saw anything like this. Odd that someone would pick a garden shed to store it in too. I did find out that a previous owner of the property had worked as a mechanical draftsman at a local tool company from shortly after WWI for about 40 years called Modern Tool in Erie, PA. This single micrometer will replace an entire set of micrometers because it can be adjusted to become anything from a 0"-1" mic to a 5"-6". Neat huh? I don't think Starrett sold it for more than a few years, and looking at it makes me think it was a pain in the **** to manufacture, and also it must have been expensive and that gave it limited appeal.

 

[rsanter]

I like it
I just wonder how accurate it is as you move ranges or if they expected you to calibrate to,a standard every time you change the range

 

[RoninB4]

I like it
I just wonder how accurate it is as you move ranges or if they expected you to calibrate to,a standard every time you change the range

-Not to be a jerk here but I check against a standard every time I pull any mic out of a box/case if i have to measure something that needs a mic. If I had a mic like that one I'd check it every time just to be able to use it a little more.

 

[TheRealZeus]

Cool you have the thumbscrew for her. nice save! This is from catalog no 17…

 

[cvairwerks]

Pretty neat and at the time quite expensive for the average tooling guy. Price adjusted to 2024 and it would be almost 700$.

 

[B Halverson]

Pretty neat and at the time quite expensive for the average tooling guy. Price adjusted to 2024 and it would be almost 700$.

Actually, if you look at how much gold you could have bought in say 1900 for the $20 this tool cost around then, it's current cost would be closer to $2800.

 

[B Halverson]

-Not to be a jerk here but I check against a standard every time I pull any mic out of a box/case if i have to measure something that needs a mic. If I had a mic like that one I'd check it every time just to be able to use it a little more.

Good practice if you are doing something critical. If I am grabbing a mic or caliper to measure a bolt I am trying to identify I am not worried if the mic is going to be close enough, but if you are measuring the rod journal of a crankshaft or a cylinder bore you are fitting piston rings to, then yes you better check your measuring tools such as mics, torque wrenches etc....

I am sure the high cost of this tool is the time it took to get all of those bushings in the right place for each position the mic is set at, to get each position accurate. I did not check all of them as I do not use the tool, but it does zero up in it's 0"-1" position nicely.

 

[rsanter]

-Not to be a jerk here but I check against a standard every time I pull any mic out of a box/case if i have to measure something that needs a mic. If I had a mic like that one I'd check it every time just to be able to use it a little more.

While that is good practice, how often you you have to adjust/calibrate the mic verses just verifying accuracy?
My point and kind of question was how accurate/consistent is this style mic from position to position as you move it? And is part of the expectation that you will calibrate/adjust it every time verses just verify as you are doing

 

[RoninB4]

While that is good practice, how often you you have to adjust/calibrate the mic verses just verifying accuracy?
My point and kind of question was how accurate/consistent is this style mic from position to position as you move it? And is part of the expectation that you will calibrate/adjust it every time verses just verify as you are doing

-I understood and agree with your original post and the question too. I wasn't trying to challenge you, please excuse my poor choice of words if it read that way. How often do I adjust/calibrate my mics? Every time I put a longer rod in the depth mic or another extension on the inside mics. I don't have to so much adjust as verifying that I don't have some grit/crud under the mating surfaces. Despite tying to keep instruments clean I found that even a film from my fingers (with surface grinding particulates) could/would migrate under the mating surfaces, particularly with the Starrett (flat adjuster nut) rods on a depth mic. The inside mics from Starrett and Lufkin are also susceptible and the error could be .001-.003 off. I also have a 0-12 mic with interchangeable anvils that wasn't always consistent for the same reasons. I bought a B&S 0-12 depth mic for the conical mating surfaces that seem to be easier to stay clean. When I find an error it tells me I need to wipe the mating surfaces better. Maybe I need to clean up my act.

 

[TheRealZeus]

Glad we ‘dialed’ that in.

 

[B Halverson]

I just looked in a 1935 Starrett catalog and this mic is still in there for sale, but at $50. So it was available for much more than a few years, sorry for yet another bad assumption. Again, $50 was a lot of money during the great depression. I once stayed in an apartment in Detroit while working there in the 1990s and there were old paycheck stubs in an attic crawlspace from Hudson from the late 1930s and the guy was making in the thirty-dollar range per week, so this tool was more than a week's wages for someone making a solid middle-class living. Also I looked at a Starrett mic I have which has replaceable anvils to give it a 1" to 4" range, it is part of an automotive measuring kit for those rebuilding engines, and it was supplied with a checking standard for each of it's ranges to make sure it was accurate after it's range was changed. Any time I used the dial-bore gauge in the kit I would first set the micrometer to the size of the bore after checking the range with a standard, then I would measure the micrometer with the dial-bore gauge before putting it inside the cylinder bore of the engine, to make sure I got the most accurate measurement of the bore possible with those tools. A bit of messing around but that is what rebuilding engines is anyway.

 

[TheRealZeus]

Cool you have the thumbscrew for her. nice save! This is from catalog no 17…

Ya patent…

US Patent: 404,057 - Micrometer Caliper

US patent 404,057 Micrometer Caliper was issued to Morris F. Smith of New Haven, CT. It was granted on 05/28/1889. This 6 inch Micrometer was #128 in the Starrett catalog. {br}This is a 0-1" micrometer mounted on a bar with a pin and a set of precision bushings. O

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