How To Read A Micrometer

Posted: November 16, 2018 By: MattM
Today we’re going to take a look at measuring with a micrometer that are available at Eastwood and show you how easy it is to use them. Micrometers are great for extremely accurate measurements and are needed when doing machine work where even small measurements can make a big difference.
We offer three sizes: 0 to 1 inch, 1 to 2 inch, and 2 to 3-inch. Adjusting and reading a micrometer is the same regardless of the size so we will so you measuring one inch. The 1 to 2 inch tool comes with a 1 inch gauge block and the 2 to 3 inch version comes with a 2 inch gauge block. The throat depths are 15/16″‘s, 1 1/4″, and 1 5/8″.
kit comes with an adjustment wrench in
The parts that make up a micrometer is the frame, spindle lock lever, sleeve thimble, and ratchet knob. When fully open it measures up to three inches with each number on the sleeve equaling one tenth of an inch or to be more precise 100,000ths. The small lines break these into quarters equaling 0.025. So if we set the tool to exactly 1/2 inch with the zero on the thimble lined up with the 5 we’re now measuring half an inch or 500 thousands. If we turn it to the first line we’ve added 25 thousands and we are now reading 525 thousands. The next line would be 550 thousandths, then 575 thousands. Another turn puts us at 6/10 or precisely 600 thousands.  The tool can measure even more precisely by using the gauge on the thimble as well. The numbers on the thimble represent every five thousand. If we turn the thimble one complete revolution you can see the 5, 10, 15, 20, and then finally back to 0 which gives us 25 thousandths we’re now at 625 thousands. You may have noticed the thimble also has two sets of lines a smaller line which should only be used for reference and the longer line which reads in thousands. That’s what we’ll be using for this measurement. So we’re now starting at 625 thousands.
Let’s say the part we’re measuring has a micrometer set at this position which now reads 642 thousands. To get here simply add the numbers. We have the 600 on the sleeve plus a 25 on the sleeve giving us 625 thousands. We now move on to the thimble, we passed the 15 by 2 big lines giving us 17 so we now add 17 to the 625 and we
arrive at 642 thousands of an inch. If the dye block is installed we’re measuring 642 thousands. Without the dye block you have to add 2 inches so we’re then measuring 2 and 642 thousands.
We realize that typically you’d be tightening the tool in the object you’re measuring, but for explanation purposes. Hopefully this quick tutorial helps you read and precisely measure things for your next project. Find our offering of Micrometers HERE.

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