What is Dial Indicator Used For? - These are the Tasks that It Does

Dial indicator is a precision measuring tool that has many functions. Its application is to measure tolerance, allowance (including clearance), circular runout, total runout, straightness, flatness, parallelism, perpendicularity, squareness, circularity, cylindricity, levelness, etc.

Therefore, this instrument is easily found in the workshop and becomes a critical part to monitor the quality of product dimensions and any other equipments in the workshop.

Unlike a micrometer or caliper that requires two surfaces to clamp to get a measurement, the dial indicator allows a single surface only. This advantage allows you to measure faster and more accurately than a micrometer such as when checking the parallelism. The micrometer requires point-to-point measurements (that take longer), while the dial indicator requires the object to slide on the surface plate and the variations can be seen on the display. And there are many other advantages of the dial indicators.

But, you will require a good magnetic stand so that the indicator doesn’t move. This is an important component that you have to acquire to gain a reliable measurement. Besides, in some cases, you require a surface plate as the plane in which this equipment is expensive.

It comes with a mechanical and digital version. Based on how the contact point moves, the mechanical model is divided into two types: plunger dial indicator and lever dial test indicator. And based on how the contact point moves, the way we use them is different as well.

The contact point movement is then engineered to be a rotational movement of the needle (the display).

As a vital measuring tool, it can measure with a greater resolution. On the market, you can find them with a resolution of .001″, .0005″, .0004″ and .0001″, depending on the models and price. In terms of measuring range, the plunger and lever indicator are also different. The plunger model (dial indicator) has a longer range while the lever model (dial test indicator) has a shorter range.

So, What is A Dial Indicator Used for?

These are the measurements or tasks that a dial indicator can handle:

1. Measure straightness

Straightness means a linear line that has only a particular length without bends or curves going in a straight line.

When machining or manufacturing any object like a straight mechanical component, a dial indicator is used to check the straightness. Other requirements you may need are a magnetic stand, some leg supports, a height gauge, a V-block, and a surface plate.

One of the examples is measuring the straightness of a cylinder bar (straight component). Put the cylinder bar on the V-block. Make sure the V-block is level. Slide the dial indicator straight along the top side of the lying bar. If the deviation is within the tolerance, it’s straight. However, if the deviation is out of the tolerance, it’s not straight.

We can also use a dial indicator to check the straightness of metal rulers, straightedge, and squares.

2. Measure Flatness

The flat can be described as multiple straight lines that stick together to become a surface. Simply, flatness is the degree of flat of a surface.

Aside from using an optical flat and CMM (Coordinate Measuring Machine), you can also use a dial indicator to measure flatness.

Put dial indicator with stand and adjustable jacks on a surface table like granite table.

Make sure the object’s surface that you want to check its flatness is in contact with the dial indicator probe. Sweep the surface with the dial indicator. Like checking the straightness, if there is a plus or minus value, there is variation. That means the surface is not truly flat. However, if the variations or deviations are under the dimension tolerance that you want, the flatness is accepted.

3. Measure Tolerance and Allowance

Basically, when it comes to measuring the straightness or flatness, you are checking whether the object is within tolerance or not. It’s the acceptable deviation. If its deviation is not under the tolerance value that has been established as the standard, they are not straight or flat. It goes the same with other properties such as squareness, perpendicularity, circularity, cylindricity, parallelism, etc.

That said, we use dial indicators to check the tolerances of any machined part.

4. Measure Circular Runout and Total Runout

Runout is the degree to which a shaft or coupling deviates from the origin or center axis. There is a center of rotation for every rotating shaft or coupling. Runout can cause excessive vibration that can lead to breakdown or accidents at high speed.

Total runout is a compound tolerance that is applied to an entire surface like any cylindrical or plan surface which includes straightness circularity, angularity, and tapers.

Hold the object on an axis, put the dial gauge V Block magnetic stand on the same axis.

Lie the cylindrical object on the V-block. Set up the dial indicator along with the magnetic base Make the dial indicator probe in contact with the top side object. Rotate the object and observe the maximum and minimum variation. It will measure around the circumference of that object.

5. Measure Squareness

Although diagonal measurements can also be used to check the squareness of any block, you can use a dial indicator to check squareness. Surely, it also requires other aspects such as parallelism, perpendicularity, and flatness of the surface. The measurement requires a height gauge to set up the horizontal plane datum.

As usual, you have to put the contact point on the block’s surface. Move the object slowly. In this way, the indicator will give any deviation from the original point of contact.

6. Measure Parallelism

Parallel is when two lines or planes are separated at the same distance. Thus, parallelism means the degree of the same distance. If they are not parallel, the extension of these two lines or planes will meet up at a certain point.

A dial indicator will sweep the surface to check the deviation. And the datum must be established in this case. Commonly, engineers use a surface plate as the datum. If the deviation is acceptable (within the tolerance zone), it’s relatively parallel. It can be not parallel depending on the high accuracy that you need.

7. Measure Perpendicularity

A line is considered perpendicular when it intersects with another line at a 90° junction. And the line must be straight (within the tolerance zone). Almost similar to squareness, perpendicularity is easy to associate with a block dimension tolerance. However, perpendicularity only addresses two sides of the block.

When a block is lying on a flat surface, you could know that one of its vertical sides is not perpendicular (not 90° and straight) by using a dial indicator and cylinder square. But this is only the case when the side is straight or flat. The deviation may address the straightness or the flatness of the block side. So, you need to check them carefully.

8. A Comparator

You can compare the height of two blocks by employing a dial indicator.

9. Measure Levelness

When checking the spirit level accuracy, a dial indicator can check the flatness of the bottom surface of the spirit level. After that, put the spirit level on a level surface. In this case, a surface plate that is level can be the datum. After the datum is ensured level, you can check the accuracy of your spirit level.

There are several applications of dial indicators that you could read on the previously mentioned. But, you have to ensure this measuring tool is calibrated so that you gain a reliable measurement.

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