How to adjust starrett micrometers

Written by brad chacos
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How to adjust starrett micrometers
Micrometers can be used for rifle adjustments. (rifle image by petar Ishmeriev from

Micrometers are an extremely accurate and simple measurement tool used in many different industries and locations, such as workshops, factories, vocational schools, automotive repair, firearm adjustments and home remodelling. According to their website, the L.S. Starrett Company has been manufacturing several types of precision tools, gauges and measuring equipment for more than 123 years, and it maintains a strong reputation for quality. Even the best-made tools lose some of their accuracy over time, especially in factory or workshop conditions, and users will probably have to occasionally adjust a Starrett micrometer to ensure reliable readings.

Skill level:

Things you need

  • Clean cloth
  • Micrometer spanner wrench
  • Calibrated standard

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  1. 1

    Wipe the faces of the stationary anvil and the lowering spindle with a clean cloth. Moisten the cloth if necessary to remove any residue or debris.

  2. 2

    Turn the ratcheting knob at the top of the micrometer to lower the spindle until it nears the stationary anvil.

  3. 3

    Use the textured portion of the rotating thimble to finish closing the spindle against the anvil. The thimble will stop lowering when contact is made, whereas the ratcheting knob will force the spindle for as long as the operator continues to turn the knob, creating offset readings.

  4. 4

    Locate the datum line on the sleeve of the micrometer and reference the "0" line on the rotating thimble. The two markings align perfectly when the Starrett micrometer is adjusted correctly.

  5. 5

    Clamp the sleeve of the micrometer in the micrometer spanner wrench, which is often included in the micrometer's carrying case.

  6. 6

    Turn the wrench to rotate the micrometer sleeve until the datum line and "0" line are matched.

  7. 7

    Check the micrometer against a calibrated standard to ensure the accuracy of the adjustment.

Tips and warnings

  • Only supervisors or inspection personnel are allowed to adjust tooling in many factories.

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