Further to Tex21 question about the depth mike.
Can anyone explain how I calibrate a set of 2-8" Mitutoyo micrometers.
It`s been a long time but I seem to remember using a set of equivalent sized outside mikes to do this, Is this correct or am I wrong again ?

Cheers Morton

It can be done with a set of O.D. mics, but you're fighting a buildup of inaccuracies. If the O.D. mics are off a few tenths, then you set the I.D. mics to them, you have a buildup. Most shoops use a ring gage, or a set of gage blocks. Say you were going to set the mic for 6", wring togeather blocks to make up 6", wring on the end caps(terminology?) and in most cases add the through bolts to hold them. Just watch temp. variations though. They can pick up enough heat from your hands to change a half thousandth.

Morton,
For what it's worth, I am an Machinist at a National Research Lab, and personally I wouldn't even consider adjusting my ID mic's. I have access to all the gages, blocks, and pins to do it, but will not! Send them to calibrating facility that has the standards, It is cheap, and they will send you certification that they are on size.
My opinion, Doug

We use ring gages, but the stacked gage blocks like mentioned by ole-270 work fine too.

I own a set of Mitutoyo ID mikes from 2" to 12" and they are all calibrated by gage blocks on a granite plate and .0001 indicators.....It's a bit finicky but it hasn't caused me any trouble ever!!!

I'd surely try to avoid using a Micrometer for the very reason stated.....it's an additional place for error to creep in.

If you have the ring gages I'd certainly use them but not many shops have such luxuries unless they was bought on some other job or contract. Darn things can be spendy!!!!