From the definition of metro-logy, a dial indicator is a measuring instrument which is used to find various metro-logical values to solve any interchangeable errors. It is used in the manufacturing processes to make an obvious product.
The configuration of a dial indicator is very simple to understand. It has a dialing display that looks like a wall clock or wristwatch.
There are several parts of a dial indicator but these two needles inside the dial display are so important to recognize. The bigger one is meant for the primary reading, while the smaller one is designed for the second reading.
The needle inside the display can move both clockwise and anticlockwise directions. It depends on the various position of the contact rod on the object surface. There is a stem rod below the dialing display that has a contact point where this measuring instrument and the object surface meet.
Depending on the positive and negative errors from the object, the contact rod moves upward and downward. The gear inside the DI transfers the linear movements into the circular movements. The circular movements are displayed on the circular dialing display. Using this instrument one can easily identify the surface size errors.
This instrument is widely used in manufacturing companies especially in the tool industry. Besides, in the local workshops, it is widely used to repair products, such as household tools, metalworking, metallic products, etc. Getting the best dial indicator is the best way to assist your metal-related jobs.
A Little About the First Dial Indicator
In the nineteenth century, the first dial indicator came from a watchmaker in England. On, may 1883 John Logan of Walt ham, Massachusetts published a journal on ‘an improvement in gages’.
The structure mentioned in the journal has no difference with today’s dial indicator. He developed a rack and pinion assembly which is used in today’s dial indicator manufacturing.
With the flow of time and the advancement of modern technology, there came many types of dial indicators. Nowadays, these measuring instruments are more accurate and precise. Though there are few types of dial indicators that didn’t match the structure with the ancient one, the working principles are still the same.
Basic Terms to Know from A Dial Indicator
Before we go for the operations, we must understand the following basic terms from a dial indicator. If we can’t understand them properly our calculations would likely have errors.
The smallest limit of the scale in making a measurement is called the graduation/resolution. Hard to understand, right? Let’s say we have a centimeter-scale that has two types of lines. One is bigger which is termed as cm line and another is the smaller that is termed as the mm line.
After 10 small lines, there is 1 big cm line. So, we can say this scale has a graduation of 1mm which is the smallest unit on the scale.
The same thing goes to the dial indicator. On the dial display, we have also two types of the line. The smaller line denotes the graduation of the circular scale. Let’s say an example, we have a 0.001″ of dial indicator which means that each smallest line indicates 0.001″. And the bigger line indicates 0.01″. So, if we complete one revolution, we will get a value of 0.1″.
Therefore, the more the graduations, the more accurate the measurement will be. The more the graduations, the smaller the value that can be measured. In general, the dial indicator having 0.001″ of the graduation is the standard model in the market. However, in some models, you can find the 0.0005″ graduation.
2. Measuring Range
Measuring range can be defined as the highest level up to which a dial indicator can measure. For example, it is said a dial indicator has a measuring range of 0-1″. It means that the dial indicator can measure until it has a complete rotation in a total of 1 inch.
There is another small circular scale inside the dial display. It counts the total number of rotations. As we know in the standard type of dial indicator, one complete rotation of the smaller scale is a measurement of 0.1 inches.
So, the smaller needle will move up to 0.1″ which means the bigger needle completed one full rotation. Similarly, a 1 inch of travel range’s smaller needle can complete consecutively 10 complete rotations of the bigger needle.
The difference between the real value and the measured value is termed as the accuracy. People get confused between the accuracy and precision of an instrument.
Accuracy and precision are two separate terms according to metrology. Precision is an average value between some consecutive values. Let’s say a dial indicator has an accuracy of 0.001″. Which means the error between the real object value and the measured value. This range is quite standard for any precision workshops manufacturing.
Calibration is a process of making an exact measurement. While looking for a dial indicator, we will find some instrument with a calibration certificate. What does it mean exactly? The calibration certificate will provide some consecutive experiment measurements where it will be said how much we should correct our reading while we go for the measurement.
Let’s say we have an accuracy of 0.001″ in our dial indicator. So, after we measure our value, we will need to adjust our value with ±001″. It will be an accurate result. We will briefly discuss this calibration in the ‘dial indicator calibration’ article.
Commonly-Used Function of A Dial Indicator
The dial indicators are commonly used in finding the tolerances. It is used for various purposes, such as measuring the value lift, measuring concentric, measuring flywheel/ brake rotor run-out, measuring gear backslash, measuring crankshaft end play, etc.
Besides, the dial indicators are also used on the CNC machine such as a lathe machine to get circular errors. We can see people using the dial indicator in the workshops. However, we can easily position the dial indicator rod against the objects which need to measure. We will elaborately discuss “how to use dial indicator” in the following articles.
This is a great precision tool that you have to purchase when dealing with precise tool-making. In terms of accuracy, as we’ve discussed, the more the graduation the more accurate the measurement can be. While measuring the value from an object we will be requiring this measuring tool.
But based on the size and types of the desired product, there are different kinds of dial indicators. We will discuss this classification in the latter article, so don’t forget to follow us. Besides, we will be also discussing how to measure values using a dial indicator properly and accurately on ‘how to use a dial indicator’ article.