Standard For Checking Inside Micrometer

Boswell

Boswell

Hobby Machinist since 2010
H-M Lifetime Diamond Member
Joined
Feb 27, 2014
Messages
2,124
I have a Mitutoyo .2"-1.2" inside micrometer that I purchased used. I would like to check the calibration. Can I go to the autoparts store and use the inside of a bearing race ? Do I need to get a master ring (Ebay has lots from $20-Thousands).

Am I even asking the right question?

Thanks
 
A master ring would be the best. You don't know what size the bearing is, but should be within a couple of tenths, it depends on how close you want to get. If you went to an automotive machine shop they should have master rings for setting their bore gauges.
 
I also have a digital Mitu .2-1.2" ID mic. I don't have a ring gauge for checking it, they're expensive! I just use an OD mic to set it. Probably not one of the better ways to do it but it works for me.
 
Do you have a outside mike that has been calibrated to a known standard such as a gage block or micrometer standard? If so, set your outside mike to a given size and measure it with your inside mike. Even though I have checked my inside mikes, to be honest, all the places I worked, everyone always measured the I.D. mike with a O.D. mike instead of relying on the I.D. mike measurement. Reason being that usually we were mating a parts id to a od size and that way you were only depending on one reference.
Of course I now realize you are referring to a actual I.D. micrometer as opposed to the standard I.D inside micrometer set with interchangeable standards. As Jim said, ring gage is best for most accurate settings.

Darrell
 
Last edited:
Boswell said:
I have a Mitutoyo .2"-1.2" inside micrometer that I purchased used. I would like to check the calibration. Can I go to the autoparts store and use the inside of a bearing race ? Do I need to get a master ring (Ebay has lots from $20-Thousands).

Am I even asking the right question?

Thanks
Click to expand...
I would not use a bearing race for a calibration standard.

It is not ideal, but you could compare it to your outside micrometer. You should have a calibration standard that is ten times more accurate than the device being calibrated but you would at least be able to see if there is a major discrepancy.

If you do get a master ring gage from e-bay, it would be preferable to have it calibrated unless it came with a current calibration certificate.
 
If you want to use a bearing race you should try to measure it with a few known good tools to see what it really measures. Otherwise you won't know if any reading you get is accurate.
 
You can also get a complete Mic calibration kit that comes with an Optical flat. If the carbide faces need lapping
this can throw off your measurements. I use gage blocks for my Etalon. And check the spindle for excess play.
With a complete set, you can check along the length of measurement. LIIS can check your mic also.
 
Like darkzero I just use an od mic. If you are just making parts in a hobby shop that is plinty good enough.
 
You must log in or register to reply here.
Back
Top