Micrometers
Micrometers measure in increments of 0.001 inches (or 0.01 mm) for such precise readings as the thickness of washers, the width of bolts and more.
Standard micrometers have three scales that measure 0.1 inch, 0.025 inch and 0.001 inch, respectively. Knowing how to read a micrometer begins with the two larger scales on the sleeve and finishes with the smaller scale on the dial or thimble.
Take these steps before a micrometer reading:
*Confirm that the horizontal line on the sleeve lines up with the 0 on the thimble. If they do not align, the micrometer needs to be calibrated.
*Press the object you are measuring against your micrometer’s anvil.
*Tighten the device until the spindle is firmly pressed against the object and has clicked 2-3 times.
*If your micrometer has a lock lever, turn it to hold the object in place.
Read the Micrometer Sleeve: Whole numbers printed on the sleeve scale represent 0.1 inch. Three small lines separate the whole numbers on the sleeve scale. These each represent 0.025 inch. Read the whole number on the sleeve first and then the quarter marks. If the whole number is a 3 followed by two quarter marks, the measurement is 0.350 inch. If the number is a 5 followed by three quarter marks, the measurement is 0.575 inch. Read the Multimeter Dial or Thimble: After you’ve read and recorded the measurement on the sleeve, check the dial or thimble, which measures in 0.001 inch. Find and record the measurement on the dial or thimble that is closest to the sleeve measurement.
Combine Your Readings: Once you have taken the measurements from every scale, combine them to determine your complete measurement. In the example presented on the diagram, the last whole number on the sleeve is 3, followed by three quarter marks (0.075) and a 6 on the thimble. The measurements would be: 0.300 + 0.075 + 0.006 Add them together and your complete measurement is 0.381 inch.
Tips for Using a Micrometer: Keep the surface of your micrometer clean of oil, dust or dirt to ensure a precise measurement. Use a soft cloth or dust rag to wipe down the spindle, anvil and measuring faces of the micrometer before and after use. Micrometers are highly sensitive, so even changes in room temperature can affect the results. When a micrometer is at the minimum setting, the horizontal line on the sleeve should align with the 0 on the thimble. If they do not line up, calibrate the micrometer with these steps: Find the adjustable wrench that came with the micrometer. Put the wrench in the small hole in the sleeve. Turn the sleeve until it aligns with the thimble. Store the micrometer at room temperature and make sure the anvil and spindle are separate in the open position. Do not store micrometers with the anvil and spindle in contact. Digital micrometers work the same as standard micrometers, but the measurements can be easily read on an LCD display. Remove batteries from digital micrometers before storing them.
