Micrometers are a small hand tool used to measure dimensions accurately to within a thousandth of an inch. Some micrometer models even utilize a small version of a vernier scale to offer a resolution of as little as ten-thousandth of an inch. The measurements a micrometer takes is only as accurate as the tool itself; however, tool wear and rough handling can misalign the thimble and spindle, resulting in inaccurate measurements. Fortunately, most micrometers come with the tool necessary to troubleshoot a screw gauge zero error.
Things You'll Need
- Micrometer spanner wrench
- Calibrated standard
Clean the heads of the micrometer's anvil and spindle.
Use the ratcheting thimble at the top of the micrometer to rotate the spindle until it rests flat against the anvil.
Check to see if the "0" measurement on the rotating thimble aligns with the datum line on the stationary sleeve.
Locate a micrometer spanner wrench if the "0" line of the thimble does not align with the datum line of the sleeve. Micrometer spanner wrenches are included in the case with most mechanical micrometer models.
Clamp the micrometer's sleeve in the spanner wrench.
Use the spanner wrench to rotate the micrometer's sleeve until the "0" line on the thimble once again aligns with the datum line of the sleeve.
Check that the micrometer reads accurately against a calibrated standard before using the tool for final or critical measurements.
Tips & Warnings
- Only supervisors or quality representatives are allowed to adjust or troubleshoot micrometers in most factory settings.
- Photo Credit antique micrometer caliper image by Michael Cornelius from Fotolia.com