Author: Yu Haidong
1 The function of vernier caliper
Vernier calipers are usually used to measure workpieces with high precision. It can measure the inner and outer diameter, length, width and depth of parts, as shown in the figure below.
2 Vernier caliper structure
The vernier caliper consists of inner diameter measuring claws, fastening screws, depth gauge, outer diameter measuring claws, vernier scale and main scale 6, as shown in the figure below.
Usually vernier calipers have 3 accuracy classifications, which are:
10 indexing vernier caliper, its accuracy is 0.1mm;
20 indexing vernier caliper, its accuracy is 0.05mm;
50 indexing vernier caliper, its accuracy is 0.02mm.
For example, a vernier caliper with 50 graduations has a total length of 49mm and is equally divided into 50 parts. The length of each part is 0.98mm. The difference between the minimum scale of the main scale and the minimum scale is 0.02mm. The accuracy of this caliper is called 0.02mm.
3 Vernier caliper measurement method
When measuring with a vernier caliper, it is generally divided into the following 5 steps:
Wipe it clean, even if the vernier caliper should be cleaned before use.
Close together, that is, bring the outer diameter measuring claw close to the outer diameter of the part being measured.
Alignment, that is, the measuring claws that are brought together and the outer diameter of the part being measured should be aligned horizontally.
The measuring claw is in close contact with the outer diameter of the part being measured.
Reading, that is, reading the measurement data of the vernier caliper, is introduced in detail below.
4 Vernier caliper reading method
① Principle of vernier caliper
Let's take the 20 graduation as an example to introduce the reading principle of the vernier caliper.
As shown in the picture above, we can see:
Each scale of the main scale is 1mm;
The total length of the vernier scale is 19mm, with a total of 20 scales, which are equally divided into 19mm, called 20 scales;
Each mark of the vernier scale is 0.05mm shorter than each mark of the main scale, and the accuracy of the caliper is called 0.05mm;
The "0" scale of the vernier scale is aligned with the "0" scale of the main scale, and the measurement result at this time is 0;
If the vernier scale moves right to the first scale after the 0 line and the first scale after the main scale 0 line, the measurement result at this time is 1 0.05mm, that is, 0.05mm;
In the same way, if the vernier scale moves right to the second scale after the 0 line and the second scale after the main scale 0 line, the measurement result at this time is 2 0.05mm, that is, 0.1mm.
Note: The accuracy of the vernier caliper with 10 indexing is 0.1mm; the accuracy of the vernier caliper with 50 indexing is 0.02mm.
② Reading method of vernier caliper
Based on the reading principle, we illustrate the reading method with an example.
As shown in the figure above, read the number of integer marks on the main scale located in front of the 0 line of the vernier scale, which is 45mm in the picture; read the number of the nearest 0.05mm mark lines on the vernier scale that coincides with the mark line of the main scale, and the number of the 5 scale lines on the vernier scale coincides with the mark line of the main scale; calculate the reading result, the result = Main scale reading + number of vernier scale coincident line digits × accuracy = 45mm + 5 × 0.05mm = 45.25mm.
5 Precautions for using vernier calipers
① The vernier caliper is a relatively precise measuring tool. It should be handled with care and must not be bumped or dropped to the ground. When in use, do not use it to measure rough objects to avoid damaging the measuring claws. When not in use, it should be placed in a dry place to prevent rust.
② When measuring the workpiece, the measuring surface of the clamp foot must be parallel or perpendicular to the surface of the workpiece and must not be skewed. And the force should not be too large to avoid deformation or wear of the clamping feet, which will affect the measurement accuracy.
③ When reading, the line of sight should be perpendicular to the ruler surface. If you need to fix the reading, you can use fastening screws to fix the vernier on the ruler body to prevent slipping.
④ When measuring the inner diameter, swing it gently to find the maximum value.
⑤ After using the vernier caliper, wipe it carefully, apply protective oil, and place it flat in the box to prevent rust or bending.
Source: Automobile maintenance technology and knowledge
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