Micrometers are tools used to make highly accurate measurements, usually of things that are difficult to measure to begin with. There are two basic types of micrometer. The screw gauge uses precisely machined screw threads on a shaft, or spindle, which is advanced and retracted to make a measurement. Calipers are designed to slide open and closed to take a measurement. Both are produced in both English and metric units. Accuracies vary depending on the type of micrometer and scale being used.
- Skill level:
- Moderately Easy
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Retract the spindle by turning the handle until the micrometer is open slightly more than is necessary for the measurement. For an outside micrometer, the opening is slightly larger than the object being measured, but for an inside micrometer, the arms are close enough together that they fit inside the object being measured.
Turn the handle until the micrometer is just grasping the object. Do not overtighten.
Use the micrometer's locking mechanism to hold the measurement in place. This could be a small lever or a thumb wheel located on either end of the handle.
Read the measurement from the micrometer's fixed scale and from the Vernier scale. Combine the two readings to get the total measurement. In the picture, the metric micrometer is showing a measurement of 5.783mm.
Open the calipers slightly more than necessary to measure the object.
Close the calipers onto the object being measured. If your calipers have an additional thumb wheel to fine-tune the measurement, use it until the object is just being held by the calipers. Do not overtighten.
Lock the calipers in place using the locking mechanism, which may be either a thumb wheel or thumb lever.
Read the measurements from the fixed and Vernier scales and combine them to get the total measurement. In the picture, the metric calipers are reading 3.58mm.