My micrometer is not calibrated anymore. What can I do? It is completely normal for a micrometer to become un-calibrated. This is easily fixed by just recalibrating it. Often, you will be able to zero a micrometer by using a small pin spanner that adjusts the sleeve in order to realign its zero line with the zero line on the thimble. Once this adjustment has been made, you can double-check the accuracy of your micrometer by adjusting it such that the anvil and the spindle faces are touching, and seeing that the micrometer reads zero. Another way in which to test the accuracy of your micrometer is to measure a standardized item, like a gauge block or rod, for which you already know the exact measurement.