Dave,
I think you are talking about how the error on each block combine to give the total error. My spacers are +/-0.0001" each. If I stack two of them up, then the worst case error is +/-0.0002". A more reasonable error would be the RMS error (root means squared error) which I figure is +/-0.00014". For 3 blocks the RMS error would be +/-0.00017".
My shop is around 60 to 90 degrees but am not sure what the temperature coefficient is for these spacer blocks. I would be surprised if it ended up anywhere need 0.002"
Rick
-----Original Message-----
From: gingery_machines@yahoogroups.com [mailto:gingery_machines@yahoogroups.com] On Behalf Of David Patterson
Sent: Monday, January 24, 2011 7:17 PM
To: gingery_machines@yahoogroups.com
Subject: RE: [gingery_machines] Re: new article: How Accurate is Your Micrometer?
Rick, when it comes to stacking gage blocks at 1" I won't make any measurable difference. If you stack blocks to get 6" you may not end up with exactly 6", as opposed to using a single 6" block. The reason is tolerance stack up.The error could be 6 microns per block for clean blocks through a little dust or cleaning solution film between them and the error would be greater. The blocks are accurate at 68 degF colder or hotter they change size. If you have a need to calibrate your micrometer, take it out and have it certified, then use it in a controlled enviroment. other than that if you can work to .002" your still splitting hairs. I'm happy with that.
Dave Patterson
http://groups.yahoo.com/group/gingery_machines/app/peoplemap/view/map
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