Thermal Insulators on Micrometers...

Splat

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If the operator is only handling a micrometer for a few seconds at a time, as a home machinist possibly might.... how important are thermal insulators on a micrometer? Are they a definite must-have on micrometers for you?
 
Apparently they do make a difference, maybe a tenth?
Mark
 
I don't worry about it. My Mit and Etalon mics have them and my Helios and B&S don't - haven't noticed a difference in use. When boring, I use a mic stand that eliminates this variable.
 
An interesting question. Steel has a linear expansion coefficient of around .000012"/" - ºC. For a six inch micrometer, if you were able to raise the frame temperature by 5ºC (9ºF), the expansion would be .00036". In practice, I expect that the temperature change caused by holding the micrometer would be no more than a degree or so, if that.

My micrometer set has the insulated grips but I measured my 5" standard and then gripped the micrometer by the uninsulated parts of the frame for about a minute. I could detect no significant change in the reading. (within .0001")
 
Tesa micrometer with 25mm range and 0.002mm resolution moved visibly after a few seconds in hand. Don't know why so much - maybe the frame distorted due to nonuniform temperature.
It wasn't nasa - just a prototype of small high speed spindle.
 
Tesa micrometer with 25mm range and 0.002mm resolution moved visibly after a few seconds in hand. Don't know why so much - maybe the frame distorted due to nonuniform temperature.
It wasn't nasa - just a prototype of small high speed spindle.

You could see it move .002 mm? You have good eyes! :)
 
Just tried this with my 2" Starrett micrometer and starting from a shop temp of 65F I inserted a 1" reference rod and zeroed it then warmed
the thing (just the frame) up as much as I could in my hands which are considerably below internal body temp, which I measured to be 86.7F.
The difference was less than a ten thousandth". There must be an expansion of the metal frame going on, and no doubt can be measured, but...
I think this is a moot point for any home machinist. Yes there will be a tiny difference, but there are a LOT of other variables to worry about that
have much greater consequences for the finished part.
 
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