Whenever we hear the name ‘screw gauge’, we come back to our old school days. Many of us used to use it during our school days in the Physics laboratory. It is not that easy to use a screw gauge all of a sudden if we didn’t use it for a long time. We have done many experiments using it and can analyze how beneficial is the screw gauge in a science student’s and an engineering student’s life.
Generally, it is used for all the measurements for tiny objects that cannot be measured by the ordinary measuring device. We can measure the radius of the wire, and so on. We all should know at least the basics of a screw gauge and how to use a screw gauge for simple work.
So, in this article, we will be discussing the procedure of how to use a screw gauge along with its advantages. There are also certain things that we need to remember as a precaution while using it. We will be discussing that as well in detail.
How To Use A Screw Gauge? – Step By Step Guide
Sometimes, while using a new device or using a device after a long time, we may find it difficult to operate it because we jumble up the process in our mind. Finally, we feel frustrated in using that device. If we write down the process step by step somewhere, it works as a savior for us.
Here, we are helping you in using any screw gauge by writing down all the procedures step by step sequentially. You can follow these steps while using the device, and after doing these two to three times, you will feel much confident about the usage of the device. So, here we go:
Total Time: 45 Minutes
Before the start of using the device, we should make sure whether the device is fit for the usage. We should smoothen the wire as well as metal sheets so that there is no error in the measurement due to any rough surface. Otherwise, it may affect the measurement to a great extent. So, make sure every part of the device is appropriately placed as needed.
Now, the next step is calibration. We need to caliber our device to prevent the wrong measurement. Without the calibration, we will end up getting some device errors. So, first, we will make sure that the grip of the screw gauge is perfect as needed. We will use the two studs of the frame and lose them. Then, we will place the wire and using the spindle; we will tighten the grip between the wire and the holding place. Make sure that the wire is held tightly. Adjust the spindle in such a way that there is no gap between the wire and the holding device.
Now, see whether the marking of both the scales is perfectly visible. It should be visible entirely; otherwise, we will end up taking observational errors. So, do the necessary changes to get the correct visibility of all the mathematical values on the device.
Now that everything is calibrated. Hold the device carefully, and don’t shake yourself. Keep yourself stiff and confident. Now, you are ready for the measurement.
Now, make a tabular column. Mark serial numbers there, at least three. There should be at least three measurements to prevent practical errors. Now marks MSR and VSR also. MSR is for Main scale reading, and VSR is for Vernier scale reading. One more important thing while doing the measurement that is the Pitch and Head Scale Count. After marking all these, go ahead with the measurements.
1. Reading a value from Vernier Scale: First, we need to find the Least Count(LC) of the given Vernier calipers. It can be calculated as MSD – VSD. Then, we need to find the zero error as Z= MSR*VSR*LC. And if you get any error, correct it as stated above. VSR is the reading that we get from the Vernier scale when it coincides with the 0 of the Main scale.
2. Reading a value from Main Scale: We need to note down the total number of uncovered and visible divisions of the main scale. MSR is the reading of the main scale that is immediately visible at the left of the Vernier scale’s 0.
Design And Specifications
Before getting into the details and procedure of using a screw gauge, we need to understand specific technical terms associated with it. We will tell you in this section about its parts. When we go further, we may use some of them while making you understand its usage. Mainly there are four parts in any standard screw gauge. So, we are mentioning its parts below:
- Screw: As the name of the device, we can think of a part named ‘screw.’ This is what is used for measurement purposes. It can measure even minute distances and lengths. It works for accuracy and precision. It has a very high resolution that helps to get the exact result. It is situated at the end of the cylindrical tube that is present on the screw gauge. The place where it is present is called Thimble. It mainly contains the Vernier scale. The Thimble can be rotated for the adjustment of the spindle. We need to see the proper adjustment to get the correct result.
- Frame: If you see a screw gauge, you can notice a U-shaped part. That U-Shaped part is called a Frame of a screw gauge. It describes the screw gauge by its unique design. It contains two studs. These are used to capture the object tightly so that the measurement can be done without any loose movement of the object. One stud is small, and the other one is large. The small stud is named Anvil, and the larger one is named spindle. The Anvil remains stationary, but the spindle is movable and rotatable.
- Barrel: This is also a very important part of any screw gauge. It is connected to the end of the frame and acts as a support to the frame. It also helps us in holding the screw gauge. Another name that you will come across for this is Sleeve. It contains a scale that is called as the main scale. We need to use both the main scale and Vernier scale for the measurement. It remains stationary as a part.
- Ratchet: For such an important device, we also require some safety measures, right? So, the ratchet is provided for this purpose. It helps us not to produce much loss to the device by applying too much pressure or rotation. Sometimes, we may end up using too much pressure on the device, or we may rotate the spindle over the limit. This ratchet works as the limiting part, which prevents every operation above a particular limit. It is the end part of the device.
Advantages Of Screw Gauge
- They are used for the measurement of very minute objects that is not possible practically by standard methods.
- It is very compact in size.
- It is effortless to handle this device.
- It is quite affordable as per cost is concerned.
- It works with full efficiency with maximum accuracy and precision.
Precautions And Sources Of Errors
Basically, there are two types of errors that can be happened during the measurement. We need to look into these errors very carefully.
- Zero Error: Two types of Zero Errors are Positive Zero Error and Negative Zero Error. This error occurs when both the scales are not set to zero initially. When the 0 is below the pitch scale level, it generates Positive Zero Error, and when the 0 is above the pitch scale level, then it is a Negative Zero Error. We can work with the scales which are not set to zero as well, but we need to keep in mind to add the zero error correction in the final result. So, there are two ways for eliminating zero error that is Zero Error Correction and by making the scales pointing zero initially.
- Parallax Error: It is just an observational error but creates a lot of mistakes if not being taken care of. We need to see precisely straight while noting down the values from the device; otherwise, there will be a slight difference from the real value, which can be a blunder for a minute measurement.
We hope that all your doubts has been cleared by this article about how to use a screw gauge. When we don’t know how to use a particular thing, then we may even lose a precious thing because we don’t know how to use it. So, we want to help all of you in understanding the correct use of a screw gauge.
You should be very clear by now in using and operating this device. There are many varieties in the screw gauge also, but when you know the usage of one type, then using other types will be very easy for you. We look forward to writing such articles to help you all if you find it useful. Thank you!