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Micrometer Standards,

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Redmech

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#1
I have a set of Micrometer standards that range from 1-12" long. All of them I have aquired used, appear in good shape, no rust, grind marks, deformation, they look great. I use them with my micrometers to measure pins, crankshafts, and anything else you could imagine that you use standards for. In all reality working in a thousandth is about all I really do, don't really worry about tenths, but it all adds up. I assume they are all "good", but I don't know, where does the community recommend I send them off to be checked/measured? I'd guess they are fine, but I work in expensive machinery, that could be detrimental if I measure a crankshaft, and cause an expensive catastrophic failure.

I'd feel much better if I know my standards are accurate.

What does this service cost, would I be better off to buy a "new" set of Mitutoyo standards off ebay 1-11" for around 200$

Thanks for any info!!!

I’ll also add they are all major name brand, Starrett, Mitutoyo, Brown and Sharpe, and maybe one NSK
 

T Bredehoft

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#2
If none of your products leave the Earth's atmosphere, you're probably good to go with the ones you have. Steel does change shape over time, so understand that what you machine to be a light press fit (measured using tools set with your standards) may not be light. Beyond that, no one's going to suffer.
I am in possession of a very old 20 inch Jo block, it was out of spec when I received it, measured beyond 20". I measured it with a then current standard bout 25 years ago, it was then 20.0009. Almost a full thou long.
 

Bob Korves

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#3
If you have any friends in the hobby in your area that have gage blocks, carefully compare the standards against the gage blocks. "Self calibration."
 

Redmech

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#4
Thanks guys, I have a 3 and 4” Johansen Jo block and the cheap set of Shars 81 piece gage block set, I’ve done a few different stacks and messed around with “self proving”, and all adds up, where each appears fine. I suspect I’m over thinking everything. My gage block set from Shars I purchased new, then all my other standards were used, the Shars I always in the back of mind maybe question it a bit, wether or not they are really checked closely, and then my used gage blocks, I just don’t know their full history.

I suspect as long as all my different stacks come up to correct calculations thru different combinations, I’m essentially self proving.

Thanks for the recommendations guys.
 

Bob Korves

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Thanks guys, I have a 3 and 4” Johansen Jo block and the cheap set of Shars 81 piece gage block set, I’ve done a few different stacks and messed around with “self proving”, and all adds up, where each appears fine. I suspect I’m over thinking everything. My gage block set from Shars I purchased new, then all my other standards were used, the Shars I always in the back of mind maybe question it a bit, wether or not they are really checked closely, and then my used gage blocks, I just don’t know their full history.

I suspect as long as all my different stacks come up to correct calculations thru different combinations, I’m essentially self proving.

Thanks for the recommendations guys.
Proverb: "Man with one watch knows what time it is." :)
 

middle.road

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#6
1.) Are you manufacturing the piece parts in a controlled environment?
2.) Is the temperature maintained to a very tight range?
3.) As Tom said - is it going into space?
Check your devices against one another off of whatever standards you have at hand. If you have the tooling - use two different mics to measure.
The ancient Starrett standards I have match up against the newer Fowlers within a couple of tenths. And this is in a garage shop with no climate control.
I've done all types of 'calibration' to trace results back to 'NIST' and at the end of the day I really have to question the cost & effort of doing so...
Save the $200 - you can 'Self Calibrate' just as Bob suggests.
 

mikey

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#7
As far as I know, you can send your mic standards to any calibration lab and they will measure and certify each one of them. They will tell you the length of each one and it should be the same in your shop IF the conditions under which they were certified is the same. If it isn't then they may be off a few microns or so. If that is acceptable then you can live with that. If a lab told me my 1" standard was 1.00004" long and my micrometer read it as 1.0000" then I could live with that. At least I know the mic is within my personal specs.
 
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