Micrometer Calibration Views
The accuracy of micrometers is checked by using them to measure gauge blocks, rods, or similar standards whose lengths are precisely and accurately known. If the gauge block is known to be 0.7500 ± .00005 ( seven-fifty plus or minus fifty millionths , that is, seven hundred fifty thou plus or minus half a tenth ), then the micrometer should measure it as 0.7500 . If the micrometer measures 0.7516 , then it is out of calibration.
The fast, economical and accurate way to calibrate a quantity of test indicators is to invest in a Dial Indicator Calibrator with the Test Indicator attachment. These mechanical devices are available in inch or metric models from several manufacturers. They are in effect a micrometer head with a large 3.5s" diameter, .00005o" accuracy and 0-1a" range. The test indicator is positioned above the spindle using the test indicator attachment. The micrometer head is rotated and readings are compared. It will be necessary to have this unit regularly calibrated by a calibration lab to maintain traceability. Ideally, readings should be taken at every numeral printed on the test indicator dial, or as your quality manual requires.
The fast, economical and accurate way to calibrate a quantity of dial indicators is to invest in a Dial Indicator Calibrator. These mechanical devices are available in inch or metric models from several manufacturers. They are in effect a micrometer head with a large 3.5 " diameter, .00005t" accuracy and 0-1n" range. The dial indicator is positioned in front of the spindle. The micrometer head is rotated and readings are compared. Ideally, readings should be taken at every numeral printed on the indicator dial, or as your quality manual requires. In practice, a reading taken every half revolution is sufficient. It will be necessary to have this unit regularly calibrated by a calibration lab to maintain traceability.
Mitutoyo suggests this procedure: wring the optical parallel to the micrometer anvil (the stationary part of the micrometer) so that only one interference fringe (light band) shows. Now close the micrometer spindle onto the parallel. This should occur exactly at .500t" when using the optical parallels in our calibration kit. At this point count the number of fringes (light bands) on the spindle by looking through the optical parallel from the other side. Then apply this formula:
Micrometer Calibration Images
