How to Read a General 102 Micrometer
Rookie Twelvemonth: The Technology Intern's Toolbox (Part 2)
A Serial of Technical Blogs for Engineering Interns & Entry-Level Engineers
"What on earth is that thing?" asks everyone who sees a micrometer for the beginning time. Who tin can blame them as it looks like something from a medieval torture chamber. And it'southward simply equally tricky to operate. "This affair takes three hands… and the numbers make no sense!" Then, why then does every veteran machinist swear that a micrometer is the best tool in their toolbox?
A micrometer is a simple and precise way to take a measurement using a manus tool. Information technology can easily and reliably measure objects to within 0.001 inches. Despite all of your negative thoughts, every engineer and machinist gets introduced to the micrometer. Often knowing how to employ i is something most companies expect interns to already understand. Hither's a quick lesson on micrometers to aid y'all stay ahead of the grade.
one. What is a Micrometer?
A micrometer is a highly precise device for measuring various objects. It operates by measuring the space betwixt a difficult end (anvil) and a movable surface (spindle). When a thimble is turned information technology drives the spindle closer or further away from the anvil. To take a measurement an object is placed betwixt the anvil and the spindle and the thimble is spun until the object is gently pinched between the two faces. After the object is pinched the scale is read and a decimal measurement is derived. *For example, 0.165 inches or four.xix mm
2. Anatomy of a Micrometer.
The basic anatomy of a micrometer is very simple. The frame of the micrometer houses all of the components that don't motion relative to the spindle. This includes the anvil, lock nut, and the sleeve. The anvil is a precision ground flat surface that acts every bit a reference. The lock nut is merely a quarter turn nut that locks the spindle from turning. The sleeve contains the scale which is used to determine the measurement and the internal threads which permit the spindle to move.
The moving parts consist of the spindle, thimble, and ratchet. Like the anvil the spindle contains a precision ground measuring face on the flat of the cylinder. The thimble acts like the caput of a bolt. When you rotate the caput it drives the bolt frontwards or backward. The Ratchet is a machinery to insure that the spindle does not pinch the object too tightly leading to a false reading.
3. Holding a Micrometer.
How you lot concur and use a micrometer will instantly tip a veteran off every bit to whether y'all know or don't know what yous are doing. Rookies typically need a third manus and excessively fumble effectually in order to accept a measurement. An one-time pro can use a micrometer in i hand and hold the item to exist measured in the other, meet Figure three. The proper way to utilize a micrometer is to concur it in your dominant hand. Grasp the thimble between your thumb and index fingers. Place the C-shape of the frame against your palm. Finally, partially wrap your pinky or band finger within the inside of the frame. Hold the object to be measured in your non dominant paw.
Quick tips:
+ Support the weight of the micrometer in your palm so you can twist the thimble or ratchet by rubbing your thumb and index fingers.
+ Don't insert your pinky or band finger into the frame and so much that you obstruct the object to be measured.
+ Don't cover the sleeve with your palm or you won't be able to see the measurement.
4. The Micrometer Calibration.
Engraved on the micrometer'due south sleeve is a scale. This scale contains a long line the runs the unabridged length of the micrometer's sleeve (datum line). In Figure iv this line is highlighted in yellow. The numbers on the scale stand for with how far away the spindle is from the anvil. The zero on the scale corresponds with the spindle touching the anvil (ie: zero distance between the surfaces). A micrometer is unremarkably ready upwards for either English or metric units only. On English micrometers each dash on this scale represents .025² (25 thousandths of an inch). The large numbers represent .100² (100 thousandths of an inch).
The spindle also contains a scale along its circumference, each of these lines are highlighted in greenish in Figure 4. Each line on this calibration represents .001² (ane thousandth of an inch). There are 25 of these lines along the spindle. Every bit the spindle revolves it will reveal more than or less of the datum line. One revolution of the spindle corresponds to .025² or one line on the datum line. Therefore, one revolution of the spindle will either reveal or hide one dash on the datum line.
5. Taking a Measurement.
To have a measurement on the micrometer the object is gently pinched between the anvil and spindle. Once a very gentle pinch has occurred the user twists the ratchet until information technology clicks once or twice. This ensures that the right amount of tension is applied. The object should be held house enough to not fall out of the micrometer under its own weight yet gentle enough that information technology can hands skid abroad if grasped. If necessary the user can employ the lock nut to prevent the spindle from tightening or loosening while interpreting the measurement.
vi. Reading the Measurement.
The user then looks at the lines on the spindle and finds which markings are aligned with the datum line. This line, highlighted with the ruby arrow in Effigy 4, is the measurement.
To interpret the measurement requires some mental math:
+ Read the largest number shown on the datum line. In Figure four, the 3 is even so visible. This corresponds to .300 inches.
+ Count the number of dashes on the datum line betwixt the final large number and the spindle. In Figure 4, i line is visible and represents .025 inches.
+ Read the number on the spindle that is aligned with the datum line. This is the line highlighted with the carmine arrow. Every bit each line is equal to .001² the highlighted line in the moving picture is read equally .016²
+ Lastly add these three numbers together to get the last measurement:
Example: .300² + .025² + .016² = .341²
7. Sample Measurements. 
Written Past: Sean Derrick – Product Evolution Engineer |
Sean has a B.S. in Engineering Design and a M.S. in Manufacturing Engineering science from Western Michigan Academy. He has over 7 years of product development experience in a multifariousness of industries ranging from medical, automotive, article of furniture, consumer products, and defense. Sean enjoys hiking, mountaineering, skiing, movies, and is pursuing a Ph.D in his free time.
Source: https://www.disher.com/2016/06/20/micro-use-micrometer/
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