# Micrometer

Fig. 1: Micrometer.

Micrometers are used to make precise measurements of small objects. An example is shown in figure 1.

## Using a Micrometer

To open and close the jaws of the micrometer you should use the friction screw on the end as this prevents over-tightening. Some micrometers have a locking lever which you should put in place once the jaws are closed on the object you are measuring.

Fig. 2: Micrometer example.

The micrometer has two scales, a coarse scale on the rod and a fine scale on the thimble. One rotation of the thimble moves the jaws in or out by 0.5mm. To take a reading, we first read off the coarse scale which will give us a reading to the nearest half-millimeter. In the example in figure 2 it is 6.5mm. Then to read the fine scale on the thimble, look at where the horizontal line on the sleeve is pointing. In figure 2 it is at 7, so the reading is 6.5mm + 0.07mm = 6.57mm.

To use a micrometer yourself, check out our interactive micrometer experiment on our ISE page.