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 discuss 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 DI, 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 we can place them easily.
- Bezel: It is the outer circular part of the DI. 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 we set the zero-reference we 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 DI. 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 of 0.001″. Generally, with the help of the pointer, we 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″ of 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. Because 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 DI with the magnetic base stand. Without this part, it’s very hard to take the readings. If we 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 DI. 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 DI. It has a very important task to do. We all know that while measuring we can’t work with the same zero reference frame. Sometimes our working object might be too high or low, it depends on its position. So, in that case, we 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, we can set any zero-reference using this top screw.
- Coil Spring: It is located at the gear near the contact rod. We 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 we 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 the dial indicator. Such as, in the digital dial indicator, we will find a digital display. As this is digital, so we 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, we 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, we 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.
We have discussed the mechanism of each part of a dial indicator. You should now understand how the pointer and hand show us the exact value. Depending on different circumstances, the mechanism of each part of the dial indicator has unique tasks to do. After all, there are a few types of dial indicators. Please click here to learn more about their types.