How to Read Dial Indicator

After learning how to use a dial indicator, you are now able to continue to how to read the dial indicator. Reading a dial indicator means calculating or interpreting the value shown by the scales. The calculation or interpretation results in an easy-to-understand number as the final reading.

It is not like reading a simple ruler, this one is more complicated but not rocket science too. There are some thumbs of rules you have to recognize.

One of the things that you need to recognize is the resolution. Most dial indicators come with 0.001″ resolution. However, it’s not rare to find them come with 0.0005″ resolution which should be the best dial indicator; the smaller the number the higher the resolution and accuracy. We cover how to read these two resolutions on this page.

Another is the scale. On the parts, you’ll find two dialing scales. Each of them provides a different scale. Keep in mind that the dial indicator and test indicator use the same reading display though they are different. Therefore, if you are learning how to read a dial indicator, you are learning to read the test indicator as well.

There are several dial indicator types available, however, the way of reading the scale basically similar. Without further ado, let’s get to the point.

How to Read A 0.001 Dial Indicator

Let’s go to the example of reading a dial indicator. Now, we are assuming that you have just observed a dial indicator position, and the state of the two dials (inner and outer dial) is described as the following:

“The needle of the outer dial (longer pointer) has completed 4 revolutions and it’s now on the number 10 at right side. The needle of the inner dial (shorter pointer) is on the 0.4 number”

To give you a better visualization, take a look at the dial indicator in the video below. Imagine that the smaller dial is stopping at 0.4 and the bigger dial is stopping at the number 10 on the right side.

  1. Observation on the inner dial: Since the outer dial travels for 4 times of revolution, the needle of inner dial now is stopping at the 0.4 number. If 10 revolutions of the outer dial account for 1.0 inch, then 4 revolutions mean 0.4 inches. Therefore, it’s easily understood that what the inner scale shows is the value.
  2. Observation on the outer dial: It is said that the dial indicator has completed for 4 revolutions. And now, it’s stopping at number 10 of the right side scale. In terms of the outer dial, forget about the revolution, focus on the number. If the needle moves clockwise, read the bigger number being observed. Read the smaller number if it moves counter-clockwise. Since the resolution is 0.001″ as marked, then it’s 10 x 0.001″ = 0.01″.

To get the final calculation, we could do it easily by adding the reading of the inner dial and outer dial. Simply, the formula is shown below:

Inner Reading + Outer Reading = Total Reading

The final calculation is 0.4″ (inner dial) + 0.010″ (outer dial) =  0.410″.

How to Read A 0.0005 Dial Indicator

The 0.0005 dial indicator means it has a graduation or resolution of 0.0005″. In other words, it can say that the smallest division on the outer dial scale of this dial indicator is 0.0005″.

Basically, there is no significant difference between the 0.001″ dial indicator from 0.0005″ dial indicator. However, for beginners, this may be confusing.

Let’s say we are using a Mitutoyo 2776S dial indicator which has 0.0005″ resolution. At a glance, it’s hard to understand how that resolution comes from. However, if we look at the inner scale (the smaller scale) carefully, we could get it.

Every two revolutions of the longer needle equal to 0.1″ reading of the smaller scale. In other words, one revolution of longer needle also represents 0.05″ reading of the smaller scale. That easy.

If you look at the Mitutoyo 2776S dial indicator closer, the smaller scale has actually 20 divisions. Each division represents one complete revolution of the bigger needle.

  1. Reading on the inner dial: Imagine that the needle stops at number 0.2. Then, simply the reading of the inner dial is 0.2 inches. If you find it stop at the mark between 0.2 and 0.3, then it is 0.25 inches. In this case, we choose reading 0.2 for easier calculation.
  2. Reading on the outer dial: In the meantime of the smaller needle is stopping at number 0.2 on the smaller scale, the bigger needle is stopping at number 15 on the bigger scale. Because there are 30 divisions (2 x 15) that is passed, it means 30 x 0.0005″ = 0.015″.
  3. Calculation: Now, let’s add them to get the final result. The total travel distance is the addition of inner reading and outer dial reading. In number, 0.2″+ 0.015″ = 0.215″.

Inner Reading + Outer Reading = Total Reading

Summary

So many points to remember right? Let’s have a glance at the summery. To use a dial indicator; we must follow these steps. Rigid mounting >> Identification of the measurement marks >> Measurement on inner and outer dial >> Calculation >> Preservation.

To read a dial indicator, you have to observe both the outer and inner dial according to their graduations. Besides, to read a 0.0005″ dial indicator we must focus on several measuring divisions.

After all, it is important to make the measurement more formal. Let’s say you have started the calculation using a dial indicator. You should follow some formal manner. So that later you can quickly get an idea about your last measured value.

To make a formal calculation, you could follow the step by step by these points:

  1. Rename your note as your company name.
  2. Note down your object name.
  3. Note down the dial indicator and its measuring range and graduations.
  4. Include the experiment date.
  5. Note the specific extension and contact point we will use for the operation.
  6. The tabulation must contain consecutive 5 values and their average.
  7. The calculation and the table must be well organized, neat, and clean.
  8. After the observation, you must preserve it for the next need.

As we know, to become a great engineer, we should be formal and experienced. You have to follow the definition of the engineering procedure so that you can get an absolute result whatever you go for measurement.