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Exact measurements are essential for many professionals, and micrometers are one of the most accurate tools on the market. Due to their sensitivity, however, even a temperature change can affect the reading.
There are three scales on a micrometer: measuring .1 inch, .025 inch and .001 inch. Take your reading by starting with the two larger scales on the sleeve and working down to the smallest scale on the dial or thimble.
Clean the Micrometer
Keep the surface of your micrometer clean to ensure a precise measurement. Use soft cloth or dust rag to wipe down the spindle and anvil of the micrometer.
Press the object you are measuring against your micrometer’s anvil. Use a vice grip to hold the frame of the micrometer and free up your hands.
Tighten the device until the spindle is firmly pressed against the object and has clicked a few times. If your micrometer has a lock lever, turn it to hold the object in place.
Read the Sleeve First
There are measurement scales on both the sleeve and the dial of the micrometer.
- Whole numbers on the sleeve scale represent .1 inch.
- Three small lines separate the whole numbers on the sleeve scale. These represent .025 inch.
Read the whole number of the sleeve first and then the quarter marks. If the whole number is a 3 followed by two quarter marks, the measurement is .350 inch. If the number is a 5 followed by three quarter marks, the measurement is .575 inch.
Read the Dial Second
Record the measurement on the dial. The smallest scale measures in .001 inch.
Some tools will have a thimble on the sleeve instead of a dial on the frame. In that case, read the number of the thimble that lines up the closest to the sleeve measurement. See the diagram below for an example.
Combine Your Readings
Once you have taken the measurement from every scale, combine them for your final measurement.
For example, the last whole number on this sleeve is 3, followed by three quarter marks and a 6 on the thimble. The measurement would be:
Your final measurement is .381 inch.
Calipers vs. Micrometers
Calipers are highly accurate precision instruments used to measure linear dimensions—such as diameter or distance between two points. They can take inside or outside measurements as well as depth and thickness.
Micrometers are similar to calipers, but they are designed for more specific measurement types. Micrometer jaws are often specialized to provide even more accurate measurements than calipers. Due to the specialized design, micrometers may be used for a specific measurement type.
Where micrometers are more accurate, calipers are more versatile.
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Use a micrometer to get exact measurements for installation or repairs. Precision is essential to professional work, and delicate measurement instruments like micrometers and calipers help.
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