set ring vs gage blocks / bore gage??

Hello all, Could some one please explain to me why you get different readings on a bore gage ( .0001 resolution) set with a set ring verses gage block or
a micrometer.My brain ( or lack of it )just cannot uderstand why there is a difference.Given the set ring is round, but still a tangency point is a tangency point, only one point of contact.Has anyone ran across this before? Or was it me setting the bore gage. This was quite a while ago , so I don't remember the exact difference. Any input would be greatly appreciated. Thanks and have a great one, Hal
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'exactly' how do they vary?
snipped-for-privacy@aol.com wrote:

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snipped-for-privacy@aol.com wrote:

Hal:
    They *should* come out exactly the same. Ring gauges are sort of self-centering - you just sweep your dial bore gauge through it. With flat gauge blocks you have to have perfect alignment in two axes at the proper point, sometimes a tricky maneuver to achieve if you don't do it often.
-- BottleBob http://home.earthlink.net/~bottlbob
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: Hello all, : Could some one please explain to me why you get different readings on a : bore gage ( .0001 resolution) set with a set ring verses gage block or : a micrometer.My brain ( or lack of it )just cannot uderstand why there : is a difference.
it's probably your feel for the gage
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I agree with BB & Kathy. It's a bit tricky aligning a bore gage with the face's of a micrometer...just keep wiggling to you find a minimum reading. You didn't specify the difference, but if it's only a tenth, it could even be just thermal expansion. If you're checking something that close, it might be prudent to do it in a temperature controlled environment.
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