Dial indicators are the measuring tool that is expressively used to measure relative positions. The internal and external mechanisms of this instrument are very simple to understand. In this article, we are going to discuss the dial indicator parts. Afterward, we will be discussing the internal mechanism of it as well. Without further ado, let’s dig in.
Structural Components of Dial Indicator
The major components of all the dial indicators are similar to each other. But except for the types of them. For example, an analog dial indicator has mechanical based components. On the other side, a digital dial indicator has digital equipment. But while taking the readings all of them got similar major components.
Following are the major components for each of the dial indicators:
- Crystal: It is the outermost part of the dial indicator, typically made of a clear plastic lens. It is right above the pointers. Bezel and outer frame hold it. Crystals are very comfortable with both the excessive sunlight vision and dim light vision. It is replaceable and you should replace them easily.
- Bezel: It is the outer circular part of the dial indicator. It can be both plastic or metallic. Few of the dial indicator has rubber bezel. It normally used to set the zero-reference on the inner dial face. Its surface is rough and movable. After you set the zero-reference, you use the top screw to tight the bezel.
- Pointer: There are two needles inside the dialing display. The bigger one is called the pointer. The pointer can be both metallic and plastic. It points to the primary readings of the dial indicator. It has a range of one complete rotation. Standard dial indicators have a range of 0 – 0.01″.
- Outer Dial: The are two dialing scale inside the display. The bigger one is called the outer dial. A standard dial indicator’s outer dial has a range of 0 – 0.01″ and graduation (resolution) of 0.001″. Generally, with the help of the pointer, you normally get the readings from the outer dial.
- Hand: The smaller needle in the dialing display is known as the hand. It takes the secondary readings. It has a range of 0-0.1″ with no graduation.
- Inner Dial: The smaller circular scale is termed as the inner dial. It has a hand to point out the readings. It has a range of 0-0.1″. Very few dial indicators have a graduation on the inner dial. Normally, one complete rotation from the outer dial denotes 0.1″ for the inner dials.
- Base Metal: Base metal is a very important part of a dial indicator. Basement holds all the gears and pinions. This part is normally made of metals. It needs to be very hard and stable.
- Screw: There are several screws in the mechanism to tightened the equipment.
- Lug back: Lug means ear. Lug back means the back which looks like an ear. Why is that? Because lug back helps to hold the dial indicator with the magnetic base stand. Without this part, it’s very hard to take the readings. If you go to fix up the instrument with the bezel, it won’t be stable in all directions. Lug back helps to hold still at any position.
- Frame: Frame is also one of the most important parts of the dial indicator. It is the main structure of the dial indicator. It is normally metallic and protects all the equipment inside.
- Top Screw: The position of this one is right at the top of the dial indicator. It has a very important task to do. It’s possible that you can’t work with the same zero reference frame. Sometimes your working object might be too high or low, it depends on its position. So, in that case, you will need to manually change the zero-reference frame. Here, this top screw works nicely. It normally tightened the hairspring gear. This gear is normally attached to the plunger directly. So, depending on various positions, you can set any zero-reference using this top screw.
- Coil Spring: It is located at the gear near the contact rod. You see that the pointer gives us the required value depending on relative positions. But did you observe that this pointer goes to zero-reference again while you separate it to the object? It happens because of this coil spring. The spring tension let the pointer goes to its original positions.
- Contact Point: The contact point is located at the lower part of the dial indicator. This is the place where the surface of the object meets. With the movement of this point, the plunger rod moves and the rack transfers the movement to the pinion, pinion transfers to the gear. Finally, with the help of the pointer attached with the gear let us know the exact value.
- Others: There are some differences in other types of dial indicators. Such as, in the digital dial indicator, you will find a digital display. As this is digital, so you will find a power supply or battery.
Internal Parts and Mechanism
Internal parts of the dial indicator consist of several gears, rack, pinions, plunger, and springs. By the way, let’s focus on the picture. Here, you can see there are 3 gears and pinions are mentioned in the diagram. Let’s describe them one by one in a sequence.
First of all, they have a plunger rod attached to the gears and the pinions. The lowermost point is known as the contact point. Here the object surface meets. Then, with the movement of the rod, the rack also drives the pinion 1 (P1), P1 then drives the first gear G1. Following this, G1 drives pinion 2 (P2). After that, The gear G1 meshes the pinion P2. P2 then drives the pinion p3.
Later on, The P3 has the pointer on the outer dial display. Lastly, P2 got the hand on the inner dial display. The hairspring let the pointer comes to its original position after the measurement. Coil spring let the plunger go its original position after it is detached from the object surface.
Those are the parts of the dial indicator as general. There are internal and external parts. The internal parts are hopefully easy to understand in order to learn the working mechanism of a dial indicator. At that point, you could understand how both the pointer and the hand work together to show us the reading. Further, these parts also lead to the classification of dial indicators. There are several types of dial indicator that will help you work more easily in a specific needs and condition.