# Micrometer Standard Set?



## Finster (Feb 4, 2016)

Anyone know where I can get a cheap mic standard set from 1"-11"? I need a set and I don't really want to spend $400+. I'm not building rocket ships for NASA so I would be happy with a cheap import set. Just something to make sure my mics are not thousands off. I tried google and the only thing that comes up are the expensive sets. They must make a cheap set in a China sweat shop somewhere. Heck, they make everything else.


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## Bob Korves (Feb 4, 2016)

Another option is to get a cheap set of gage blocks, which could also help with other tasks as well.  Typical gage block sets come with 4", 2", 1", and a bunch of smaller ones.  If you purchased an additional 4" block, you would be set.  If you search around you can find new import sets for $100 or thereabouts.  Used ones are also a possibility.  They are also easier to use with outside mics than regular standards, IMO.  For a 11" stack you might also want to buy or make a fixture to hold them together.


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## RJSakowski (Feb 4, 2016)

They get shipped with the micrometers so probably not a lot of demand for a set.  

You could make up your own.  They don't have to be dead on.  Make up a set and "calibrate" them with a set of known good micrometers. It violates the rule of having your calibration standard  at 3 -10 times better accuracy than the instrument being calibrated but is better than nothing.


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## Finster (Feb 4, 2016)

Bob Korves said:


> Another option is to get a cheap set of gage blocks, which could also help with other tasks as well.  Typical gage block sets come with 4", 2", 1", and a bunch of smaller ones.  If you purchased an additional 4" block, you would be set.  If you search around you can find new import sets for $100 or thereabouts.  Used ones are also a possibility.  They are also easier to use with outside mics than regular standards, IMO.  For a 11" stack you might also want to buy or make a fixture to hold them together.


Yea, I thought of that actually but I'm not sure just how accurate it would be. Stacking a bunch of blocks could have a high possibility of error IMO. A stray chip here or there that I miss and everything is messed up. It's a good idea but I think it would drive me crazy. I would be checking things a hundred times before I was satisfied. However, I may go that route if I must. Thanks for the advice.


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## RJSakowski (Feb 4, 2016)

The standard method of calibrating a micrometer is as Bob K has stated.  Gage blocks should be properly cleaned and wrung together.


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## Bob Korves (Feb 4, 2016)

Gage blocks are used by wringing them together after wiping them on the back of your wrist.  If they stick together, there is nothing between them that will make a difference.  The inherent accuracy of gage blocks makes them well more than accurate enough for what you are trying to do, even with several stacked up.  I have no idea what the tolerance is on mic standards, but I would bet gage blocks are used in the testing process during their manufacture...


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## Finster (Feb 4, 2016)

Yea, I'll probably go that route. I didn't realize how cheap grade B's were. You can get a 81 piece set on ebay for $75. I've never owned a set but used to use them years ago at work. Humph! I thought they were much more expensive and grade B's are fine for me. Thanks guys.


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## Tony Wells (Feb 4, 2016)

The beauty of standards for you mics is that they don't have to be spot on, you just have to know what they actually are. I use to send out every mic standard in the shop I ran QC on, and they came back certed with actual sizes on them. I then gave them back to the respective owners. Even brand new standards are not exact (what is?) but assumed to be accurate enough to use with the mic it is sent with. Get some drill rod and using your DRO, make some as close as you can, dome the ends slightly, and either have them certed or at least let someone with known good micrometers give you a reliable number to use. Just be aware that if they are soft, and you use them a lot, they will get shorter so need to be rechecked and marked periodically.


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## Finster (Feb 4, 2016)

Great advice everyone.


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## Uglydog (Feb 4, 2016)

If you have extra  mics laying around, then when you calibrate them, consider leaving your best most accurate, favorite mic with your inspection plate. 
Keep it there. 
Take the others into the swarf and oil with your machines. There the odds of them getting dropped, or just used hard are higher.  
Much easier on the good stuff. 

Daryl
MN


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## owl (Feb 4, 2016)

One caution, for your larger standards, they are very temperature sensitive.  A 10" standard will grow .00065" for every 10 degree Fahrenheit rise.  Of course if the mic and standard both have similar temp rise, there could be cancellation errors.


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## kd4gij (Feb 4, 2016)

Our calibration lab uses gage blocks to calibrate the mic's.


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## T Bredehoft (Feb 4, 2016)

owl said:


> A 10" standard will grow .00065" for every 10 degree Fahrenheit rise



You're number's right, I always did it this way. On a calculator,  enter inches, enter difference in temperature in f, enter 5 0's (.00000) followed by 66, 63 for cast iron. hit enter. After a while  you get good at feeling differences in temperature.


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## Uglydog (Feb 6, 2016)

Another option might be to use end measures. Especially for very large sizes. Certainly cheap enough. 

Daryl 
MN


Sent from my iPhone using Tapatalk


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## British Steel (Feb 9, 2016)

T Bredehoft said:


> You're number's right, I always did it this way. On a calculator,  enter inches, enter difference in temperature in f, enter 5 0's (.00000) followed by 66, 63 for cast iron. hit enter. After a while  you get good at feeling differences in temperature.



Some of us have sources of Invar 36 bar ("take it away, we need the space and we lost the certificates...") - so add another zero*, and access to Zeiss Coordinate Measuring Machines used for *calibrating* other CMM standards, at work.... 

If you have a few good known length standards, then anything else can be calibrated from 'em with a little ingenuity!

I love the skip at work - even though my boss says it's "unprofessional", I'm not giving up my intimate relationship with it 
Now I wonder whether they're going to scrap any Inovco... $

Dave H. (the other one)


* 1.2 ppm/C, 0.67 ppm/F
$ 0.55 ppm/C - but only from 20 - 100 C...


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## Tony Wells (Feb 9, 2016)

oooh Invar......good stuff


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