Micrometer Measurements

[buffalo]

Have slugged the bore on a revolver.I had an older micrometer that I was having problems reading.I then realized when I could see it I didnt know how to read the calibrations.Bought a new Mutitoyo Digital that I can read and understand.It is very sensitive. My question is how much pressure should one use to measure the bullet? If it barely touches the bullet you get a reading but if you tighten the anvil you get smaller diameters. How do you know what tightness to use? Thanks

[bilmac]

My mechanical micrometers have a stem on the bottom of the turning dial that is clutched, it spins independently of the dial when a certain amount of torque is applied. I always tighten the dial using this stem. I would hope that your digital would have one too.

[Veral]

  The clutched stems are quite standard on higher grade micrometers, and perhaps it is wise for people unfamiliar with precision measuring to use them.
  However, I never use the little spindle but close the mic till it makes a good firm contact yet lets the part slip out easily.        To check the calibration of a one inch micrometer, place a clean sheet of strong paper like typing paper, between the anvils, snug the anvils done lightly and slide the paper out.  This will clean them perfectly,  Now close the mic with the same pressure you'll be applying when you take measurements.  If it doesn't read 0, adjust the mic till it does.  The mic will then be adjusted for the pressure you apply when measuring.  Note that I said this information was for 1 inch mic's, which is all most shooters will be using.  For larger mic's the anvils will have to be cleaned another way and a standard used for calibration.

[bilmac]

Thanks Veral, I never had any instructions either, just did what comes naturally.