Before using micrometer standards or measuring rods to calibrate your micrometers or calipers, practice using them on a new gage, or one that has just been certified. This allows you to check that you can get the same readings, time after time, with your rods. When you are confident that you have mastered the technique, you can move on to your other gages. Measuring rods do not actually "wring" to the surfaces of your micrometer or calipers, but you have to eliminate all sideways play, however minute, and this is done somewhat like wringing gage blocks. Since holding the measuring rod horizontally is a bit like balancing a beam, you may find that holding the rod and the tool vertically gives you more reliable results. Finally, be sure that your measuring rods and your calipers or micrometers are both at room temperature. If you don't think this matters, just try an experiment. You can easily be off by .001" over 4 inches if the calipers are in an air-conditioned room and the rods have been out in the summer heat.
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