1. How to Read a Micrometer
Jefferson College
Area Technical School
Applied Mathematics

2. The Micrometer
A micrometer generally provides greater precision than a caliper, but can measure a smaller range of lengths.

3. Parts of a Micrometer
A standard outside micrometer has a U-shaped frame, an anvil, a spindle, a sleeve or barrel, and a thimble

4. To use a Micrometer…
Place the object to be measured in the opening and turn the thimble until the spindle contacts the work.
Use the ratchet stop to apply a consistent pressure to the part.
Use the clamp ring to hold the thimble in place while you read the micrometer.

5. To read the Micrometer…
Read the exposed number on the barrel 0,1,2,3,4,5,6,7,8,9. Each of these division represents inch.
Read the number of divisions past the number. Each of these division represents inch.
Read the division on the spindle. These usually read to one thousandth of an inch.

6. …cont
Each of the 25 marks on the thimble represents inch. Each complete turn on the thimble equals inch.
Each division on the sleeve is equal to inch. Four divisions are equal to inch (4 x = 0.100).
Therefore, four complete rotations of the thimble will equal inch.
Note the number of lines on the sleeve that are exposed, starting with zero.
Count the number of lines that show.
Add to this the value of the lines such as 0.025, 0.050, or

7. …cont
To this reading, add the number of divisions on the thimble from zero to the line that coincides with the index line on the sleeve.
The index line is the long line that runs lengthwise to the sleeve. All thimble readings are taken from the line on the thimble that lines up with this index line.

8. Example 1 The last large Number is 1 so we have .100
we have two lines past the 2 so we have .050
and the thimble is turned to the 0 so we have 0
add it together and we have .150

9. Example 2 The last large Number is 2 so we have .200
we have two lines past the 2 so we have .050
and the thimble is turned to the 5 so we have .005
add it together and we have .255

10. Example 3 The last large Number is 2 so we have .200
we have two lines past the 0 so we have 0
and the thimble is turned to the 19 so we have .019
add it together and we have .219