According to the definition, either a micrometer or a caliper is an instrument designed to provide highly accurate measurements. They measure linear dimensions such as diameter and thickness. We use them to measure the distance between two opposite sides of an object.
At a glance, it might be difficult to differentiate them from the definition itself. Both micrometers and calipers seem similar. They both are designed for precision measurement and basically to measure linear dimensions. However, if we discover further, they actually have a bunch of differences.
1. Body Parts
First of all, the comparison starts with body parts. A micrometer has the following body parts:
- C-Frame: The C-frame is the rigid part of the micrometer. It represents how long the range of the measurement can support. It’s to provide support to the anvil and the spindle of the micrometer.
- Anvil: Anvil is the cylindrical part of the micrometer that is present at one side of the C-frame. It is one of the holding points of the object to be measured. Anvil is a stationary and fixed part.
- Spindle: It is the other cylindrical part, connected to the sleeve, thimble and the ratchet. It is a moveable part and its movement is adjusted according to the size of the object.
- Sleeve: The sleeve is the basic scale of the micrometer and the thimble rotates around it. Also, it’s a stationary component of a micrometer.
- Thimble: The thimble is the secondary scale, it rotates and revolutes around the sleeve. You can take readings when the value on the thimble scale aligns with the index line.
- Ratchet: Ratchet is a rotatable cylindrical component at the end of the micrometer. It moves the spindle in the desired axial direction and gives an allowed pressure to the object to be measured in order to get a precise measurement.
While the following is the caliper body parts:
- External Jaws: The part of caliper which makes a contact to the object to be measured is called jaw. External jaws function to become the measuring faces of the measurement of the outside dimension.
- Internal Jaws: To measure such as the inside diameter of an object, the internal jaws come into play to do that job. It secures the object from the inside dimension.
- Fixed Jaws: It’s the stationary jaws, found both in external and internal jaws. It cannot be moved.
- Sliding Jaws: It suits the length of the object to be measured. Therefore, it can slide depending on the object-to-be-measured length.
- Fixed Scale: A vernier caliper has two scales, one is the fixed main scale. It contains the graduation in mm or inch.
- Sliding Scale: Like its name, it can slide and suit the length of the object to be measured. On the sliding scale, the vernier scale takes place. Similarly, it is in metric and imperial graduation.
- Locking Screw: It functions to tighten the holding to the object to be measured. After the jaw grip the object, lock the sliding scale with the locking screw to prevent it from slipping.
If we make a comparison, then the results are:
- Micrometers have a U-shaped frame, while the calipers don’t.
- To secure the objects, the micrometers have anvil and spindle. While the calipers, both for internal and external measurements, use the fixed and sliding jaws to hold the object.
- Both of them have two scales in which one is fixed and the other is movable. However, the micrometers commonly have additional vernier scale which makes it has three scales in total. It shows that micrometers can support better accuracy.
- Locking nut is the locking system in micrometers. Similarly, the calipers have a locking screw to tighten the object. Both of them have a mechanism to lock the measurement to prevent sliding.
- Ratchet is an excellent part of a micrometer. Since micrometers can support to measure within micron resolution, any overpressure can impact. A ratchet comes to give an allowed and predetermined pressure to the objects so the measurement can be reliably accurate. While the calipers rely on your sense of pressing, it’s not as accurate as the micrometers.
So, the body parts that differentiate them are the frame on micrometers, the ratchet, and the cylindrical spindle on the micrometers which are different than the calipers. In calipers, the moving part is the sliding which contains the vernier scale as well. The rest of them basically has the same mechanism.
2. Measurement Purposes
Since calipers and micrometers have different body parts, the measuring purposes of both are different. Calipers have multiple functions, while micrometers only have a specific function.
Calipers have some measuring jaws which allow them to be able to do 3 kinds of measurement in one tool. In contrast, micrometers have only one fixed anvil that only able to do 1 kind of measurement. Mostly micrometers have flat anvil which restricts measurement only for outside diameter and thickness. To measure the internal diameter, the user should switch over to another micrometer which has a specific anvil that is suitable for it. Similarly, to measure the thickness, you need a spherical flat micrometer such as those in reloading micrometers.
If you are going to measure different sorts of tasks, then you have to prepare different sorts of micrometers. Fortunately, you only need one caliper to measure a wide range of tasks such as internal diameter, external diameter, depth, and even thickness. This is a winning deal of calipers instead of micrometers in terms of its versatility.
3. How They Work
Both micrometers and calipers use the amplification principle of the main scale. For example, the micrometers are in metric version and the smallest graduation of the main scale is 1mm. The 1mm of the main scale is then amplified in such a way into smaller graduations. However, the 1 mm space is too small to put more graduations, therefore the second scale presents to magnify it.
The thing comes differently to the way it magnifies. The way the 1mm space magnifies is different from each other between the micrometers and calipers. Micrometers employ the contribution of the threaded spindle, while the calipers use the sliding frame. Therefore, the way we use micrometers is by rotating it. And we slide the frame while using calipers. Certainly, this behaves to mechanical micrometer and vernier caliper.
For the dial and digital type, there is no significant difference between them. It uses dial gauge which contains racks and pinions inside the tool.
The digital, in contrast, is quite different in spite of using electronic components. The digital micrometer employs cylindrical capacitive components to convert the electric charge into numbers. While the digital calipers manipulate the charge by using rectangle capacitive components which slides over the main scale.
4. Resolution / Accuracy
The least count, it frequently refers to the term “resolution”, is also the most contrast aspect when we identify these two precise measuring tools. Therefore, while calipers provide accurate measurements, the micrometers can provide more accurate ones than the calipers.
The least count of the vernier calipers ranges from 0.1mm to 0.02mm, by comparison, the least count of the micrometers ranges deeper from 0.01mm to 0.001. Even, there is a micrometer made by Mitutoyo that reaches 0.0001mm measuring least count. As its name “micrometer”, the micrometer can measure down to micron size.
5. Price Range
Price is also one of the factors that differentiate them. Since one of them needs higher accuracy on the components, the most accurate one is reasonably the more expensive one. Surely, micrometers have a higher price than calipers.
For a kind of digital calipers, you could afford it about $20 for the cheapest ones. In contrast, you need at least about $50 to get a single digital micrometer. For digital calipers, it ranges approximately from $20-$200. While digital micrometers range from about $50-$500.
6. The Uses
Both micrometers and calipers are instruments that have the ability to measure small dimensions. Therefore, they are widely used in mechanical engineering, engine building, various industries, medicine, construction, hobbyist, metalworking, home use, school, etc. However, in case the users need higher precision, instead of choosing calipers, they tend to need micrometers.
7. Chances of Error
An error can be caused while taking the measurements in both of the devices. It may be caused by personal and faulty apparatuses as well. It is very necessary to make sure that your apparatus is properly functional. If the edges or corner are bent, you will definitely not be able to get the results you are looking for.
Typical vernier calipers and micrometers both require practice and experience. In this regard, they are not quite different. If the user is not careful or experienced, it is likely that there will be a chance of error.
In addition, if the faces of the micrometer which are the anvil and spindle, they are not properly flat then the readings will also not be reliable. If the jaws of the vernier calipers do not properly function, the same thing will happen.
If we talk about the zero error, then both the devices can have it. However, if you know the right way to calculate it then you get accurate readings. Zero error is mostly observed in vernier calipers but it can be added or subtracted to the original value.
In summary, we can merge each difference of them into a single list below.
- The focus of the calipers is on the internal size and external size of the objects while the micrometers deal with just one of them, can’t be flexible or multiple uses, and extremely small objects.
- Micrometers measure the thickness and distances between small objects. They are specifically designed to get smaller measurements as compared to calipers.
- The micrometer only takes external measurements while the vernier caliper can take internal and external measurements both.
- The basic difference can be identified from their structures and working. They may have a similar functioning but the structure of each of the instrument is totally different.
- The micrometers are more accurate as compared to calipers because they have the ability to measure extremely small measurements.
- The least count of the caliper is 0.1mm while the least count of the micrometer is 0.01mm, which means micrometer can measure the very small distance of a dimension.
- When we talk about the functioning of the two instruments, we see that the calipers have a sliding scale with which the readings are taken and on the other hand, micrometer has a rotating scale.
- If we compare the costs, we will see that the micrometers are cheaper than the calipers. The digital calipers are very expensive as compared to micrometers. Also, if we look for a specific type of micrometer that may also be slightly expensive as compared to a typical micrometer.
On the other hand, both of them have similarities such as:
- Both of the instruments are used in the various field, they are used in woodworking, engineering, and mechanical fields as well.
- The vernier caliper is most likely to have zero error, micrometers might have zero error as well. The zero error can be easily calculated and removed.
While comparing the micrometer and caliper, we observed that there are quite a few similarities and quite a few differences. However, they both are designed for the same function that is measuring object. One measures the internal size, external size, and the depth, while the other measures the thickness of the objects. It depends upon the need of the individual that which instrument he will adopt for a specific purpose. Both of them are quite accurate but they do require practice and experience.