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05 September 2003

Measuring with a Micrometer

Source: Mechanical Engineering Dept., MIT

A micrometer generally provides greater precision than a caliper, but can measure a smaller range of lengths. A micrometer is depicted in the drawing below.

To use a micrometer, place the item to be measured in the opening. Next, turn the thimble until the spindle contacts the work. To apply a consistent pressure to the part, use the ratchet stop. Use the clamp ring to hold the thimble in place while you read the micrometer. To read the micrometer:

• Read the exposed number on the barrel.
• Read the number of divisions past the number. Each division represents 0.025 inches.
• Read the division on the spindle. These usually read to less than thousandths of an inch.

An example of reading the micrometer follows:

Click image to enlarge