Did You Use the Wrong Vernier Caliper and Micrometer?

Vernier caliper is an instrument commonly used in industry to measure length. It can be directly used to measure workpieces with high precision, such as the length, inner diameter, outer diameter and depth of the workpiece.

Overview of vernier calipers

As a widely used high-precision measuring tool, the vernier caliper consists of a main scale and a sliding vernier attached to the main scale. If divided according to the scale value of the vernier, the vernier caliper is divided into three types: 0.1, 0.05, and 0.02mm.

Vernier caliper reading method

Taking a precision vernier caliper with a scale value of 0.02mm as an example, the reading method can be divided into three steps;

1) Read the whole millimeter according to the nearest scale on the main ruler to the left of the zero line of the auxiliary ruler;

2) According to the zero line of the auxiliary ruler, multiply the number of lines aligned to the right with the scale on the main ruler by 0.02 to read the decimal;

3) Add the integers and decimals above to get the total size.

Reading method of 0.02mm vernier caliper

As shown in the picture above, the 0 line of the auxiliary ruler is aligned with the scale in front of the main ruler 64mm, and the 9th line after the 0 line of the auxiliary ruler is aligned with a engraved line on the main ruler.

The 9th line after the 0 line of the secondary ruler indicates: 0.02x9= 0.18mm

So the size of the workpiece to be measured is: 64+0.18=64.18mm

How to use vernier caliper

Put the measuring claws together and check whether the zero mark of the vernier and the main scale body are aligned. If aligned, you can measure: If not aligned, zero error must be recorded: if the zero scale line of the cursor is to the right of the zero scale line of the ruler body, it is called a positive zero error, and if it is to the left of the zero scale line of the ruler body, it is called a negative zero error (this This method of specification is consistent with the specification of the number axis, with the origin on the right being positive and the origin on the left being negative).

When measuring, hold the ruler body with your right hand, move the cursor with your thumb, and hold the object to be measured with the outer diameter (or inner diameter) in your left hand, so that the object to be measured is located between the outer measuring claws. When it is tightly attached to the measuring claws, you can Reading, as shown in the figure below:

Application of vernier caliper

As a commonly used measuring tool, vernier calipers can be specifically used in the following four aspects: 

1) Measuring the width of workpieces

2) Measure the outer diameter of the workpiece

3) Measure the inner diameter of the workpiece

4) Measure the depth of the workpiece

Please see the figure below for the specific measurement methods of these four aspects:

Precautions for use

Vernier calipers are relatively precise measuring tools. When using them, you should pay attention to the following matters:

1. Before use, clean the measuring surfaces of the two clamping feet, close the two clamping feet, and check whether the 0 line of the auxiliary ruler is aligned with the 0 line of the main ruler. If they are not aligned, the measurement reading should be corrected according to the original error.

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, otherwise the measurement value will be inaccurate.

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 closure. To prevent rust or bending.

The spiral micrometer, also called a micrometer, is a precision measuring tool. The principle, structure and use of the spiral micrometer will be explained below.

What is a spiral micrometer?

The spiral micrometer, also known as micrometer, spiral micrometer, and centimeter, is a more precise tool for measuring length than a vernier caliper. It can measure length accurately to 0.01mm, and the measurement range is several centimeters.

Working principle of spiral micrometer

The spiral micrometer is made based on the principle of spiral amplification, that is, when the screw rotates in the nut for one revolution, the screw advances or retreats a pitch distance along the direction of the rotation axis. Therefore, small distances moved along the axis can be expressed by readings on the circumference.

The pitch of the precision thread of the spiral micrometer is 0.5mm. The movable scale has 50 equal divisions. When the movable scale rotates once, the micrometer screw can advance or retreat 0.5mm. Therefore, rotating each small division is equivalent to measuring The micro screw moves forward or backward by 0.5/50=0.01mm. It can be seen that each small division of the movable scale represents 0.01mm, so the spiral micrometer can be accurate to 0.01mm. Because it can also read one more digit, it can read to the thousandths of a millimeter, so it is also called a micrometer.

How to use a spiral micrometer

When we often help customers use spiral micrometers to connect to our data acquisition instruments for efficient measurements, we often guide customers to do the following when making spiral micrometers:

1. Check the zero point before use: slowly turn the fine-tuning knob D′ to bring the measuring rod (F) and the measuring anvil (A) into contact until the ratchet makes a sound. At this time, the zero point on the movable ruler (movable sleeve) The engraved line should be aligned with the reference line (long horizontal line) on the fixed sleeve, otherwise there will be zero error.

   
   

2. Hold the ruler frame (C) with your left hand, turn the coarse adjustment knob D with your right hand so that the distance between the measuring rod F and the measuring anvil A is slightly larger than the object to be measured, put in the object to be measured, and turn the protection knob D′ to clamp the object to be measured until Until the ratchet makes a sound, turn the fixing knob G to fix the measuring rod and take a reading.

How to read a spiral micrometer

1. Read the fixed scale first

2. Read the half scale again. If the half scale line is exposed, record it as 0.5mm; if the half scale line is not exposed, record it as 0.0mm;

3. Read the movable scale again (pay attention to the estimated reading) and record it as n×0.01mm;

4. The final reading result is fixed scale + half scale + movable scale

Because the reading results of the spiral micrometer are accurate to the thousandth of a millimeter, the spiral micrometer is also called a micrometer.

Things to note about spiral micrometers

1. When measuring, be careful to stop using the knob when the micrometer screw is close to the object being measured, and use the fine-tuning knob instead to avoid excessive pressure. This can not only ensure accurate measurement results, but also protect the screw micrometer.

2. When reading, pay attention to whether the half millimeter mark on the fixed scale is exposed.

3. When reading, there is an estimated reading number on the thousandth place, which cannot be thrown away casually. Even if the zero point of the fixed scale is exactly aligned with a certain scale line of the movable scale, the thousandth place should still read "0".

4. When the anvil and the micrometer screw are brought together, the zero point of the movable scale does not coincide with the zero point of the fixed scale, and a zero error will occur. This should be corrected, that is, the zero error value should be removed from the final length measurement reading.

Correct use and maintenance of spiral micrometer

• Check whether the zero line is accurate;

• When measuring, the surface of the workpiece to be measured needs to be wiped clean;

• When the workpiece is large, it should be measured on a V-shaped iron or flat plate;

• Wipe the measuring rod and anvil clean before measuring;

• A ratchet device is required when twisting the movable sleeve;

• Do not loosen the back cover to avoid changing the zero line;

• Do not add ordinary engine oil between the fixed sleeve and the movable sleeve;

• Wipe it clean and oil it after use, put it in a special box and keep it in a dry place.