Vernier scale is a kind of measurementlength, internal and external diameterdepthOfMeasuring tools。The vernier caliper consists of a main ruler and a sliding one attached to the main rulercursorTwo parts;Viewed from the back, the vernier is a whole, and the depth gauge is connected with the vernier to measure the depth of the groove and cylinder.
The main ruler is generally in mm, and there are 10, 20 or 50 divisions on the vernier. According to the division, the vernier caliper can be divided into ten division vernier caliper, twenty division vernier caliper, fifty division vernier caliper, etc. The vernier caliper with 10 divisions is 9mm, 20Indexing19 mm for 50 divisions and 49 mm for 50 divisions.There are two pairs of movable measuring jaws on the main ruler and vernier of the vernier caliper, which are internal measuring jaws and external measuring jaws. The internal measuring jaws are usually used for measuringinternal diameter, external measuring jaws are usually used to measure length andexternal diameter。
The vernier caliper has the characteristics of simple structure, convenient use, medium precision and large measurement range.It can be used to measure the inner diameter, outer diameter, length, width, thickness, depth and hole spacing of parts. It is a universal measuring tool with a wide range of applications.[1]
Chinese name
Vernier caliper
Foreign name
vernier scale
Alias
vernier、Straight vernier、Vinier calipers
Pinyin
yóu biāo kǎ chǐ
Definition
Measuring tool for measuring length, internal and external diameter and depth
In all kinds of measuring instrument families, vernier caliper, as a widely used high-precision measuring tool, is the extension and expansion of scribed ruler, which originated in China.In the early ancient times, length was mainly measured by means of wooden poles or ropes, or by means of "stepping" and "hand cloth". When the length unit system was established, the scribed lines appearedruler。This ruler was used in ancient Egypt in 3000 BC, and in China in 2000 BCXia and Shang DynastiesIt was mainly made of ivory and jade at that time, until the appearance of bronze line ruler, which was an "advanced" measuring tool, was more used in production and astronomical measurement.
In the Han Dynasty, China developed science and technology and invented a large number of advanced instruments and appliances that were ahead of the world at that time, such asArmillary sphere、Seismograph, water drain, etc. These circlesShaft partsThe birth of the ruler marks the birth of the ruler in China.The "Xinmang Copper Caliper" collected in the National Museum in Beijing is the earliest calipers found in the world through expert research. It was made in AD 9, more than 2000 years ago.Compared with our country, the foreign invention in the field of calipers is more than 1000 years later. The earliest is the British "caliper", which looks like a vernier caliper, but like the Xinmang copper caliper, it is only a scribed caliper, with low accuracy and scope of use.
Figure 2 Copper Calipers of the Eastern Han Dynasty
The vernier caliper with the most modern measurement value is generally believed to be invented by the Frenchman Pierre Vinier.He is a famous mathematician who described the structure and principle of the vernier caliper in his mathematical monograph Structure, Use and Characteristics of the New Quadrant, and his name Vernier has become the English word vernier.The famous vernier caliper was not seen, so some people questioned whether he had made it.In the middle of the 20th century, the American machinery industry developed rapidly. In the autumn of 1985, the founder of Sharp Machinery Co., Ltd. successfully processed the world's first batch of four 0-4 inch vernier calipers, with an accuracy of 0.1 mm.In 1851, the United States Brown&Sharpe Company manufactured the first vernier caliper based on the ideas of Nonuth and Vernier, which was improved and manufactured by Masuer Arsenal in Germany. It is the most widely used measuring tool in engineering.In 1854, vernier calipers were widely used in Netherlands, France, Germany, Britain and Japan. In 1856, vernier calipers were also popularized in Japan. The manufacturing technology of vernier calipers was gradually updated and rapidly improved, making it a universal length.In May 1992Yangzhou City8km northwestHanjiang CountyGanquan Township (today's Hanjiang DistrictGoodsprings ）A brick chamber tomb in the early Eastern Han Dynasty was successfully cleaned, and a copper caliper (see Figure 2) was unearthed from the tomb. The copper caliper consists of fixed ruler, movable ruler and other parts.The fixed ruler is 13.3cm long, and the fixed jaw is 5.2cm long, 0.9cm wide and 0.5cm thick.There is a fish shaped handle at the upper end of the fixed ruler, which is 13cm long. A guide slot is opened in the middle, and a guide pin that can rotate and adjust is built in the slot, moving left and right along the guide slot.A ring handle is connected between the movable ruler and the movable jaw, which is convenient for tying rope or grasping.When the two claws are parallel, the fixed ruler is equal to the movable ruler.When using, hold the fish handle with your left hand, pull the ring handle with your right hand, and pull it left and right to measure the workpiece.Use thisMeasuring toolsIt can measure not only the diameter of objects, but also their depth, length, width and thickness, which is more convenient and accurate than a ruler.Due to its long history, its fixed ruler and movable ruler are rusted and hard to recognize.The discovery of the original copper calipers in the Eastern Han Dynasty corrected the idea that the vernier calipers were invented by European and American scientists in the past.The British Encyclopedia, Vol. 10, page 402, published in 1973 in Britain, recorded that the vernier caliper was invented in 1631 by the French mathematician "Pierre Vernier" (1580-1637 AD).
Structure composition
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The main body of the vernier caliper is a ruler body engraved with a scale, called the main ruler. The ruler frame sliding along the main ruler is equipped with a vernier (ruler).In addition, the vernier caliper is composed of upper measuring jaw, lower measuring jaw, depth gauge and set screw.The main ruler and the upper and lower measuring claws fixed on the left side are made into a whole, and the auxiliary ruler and the upper and lower measuring claws movable on the right side are made into another whole, which is sleeved on the main ruler and can slide along the main ruler.The structure of vernier caliper is shown in the following figure:[2]
There are 10, 20 or 50 divisions on the vernier. According to the division, the vernier caliper can be divided into ten division vernier caliper, twenty division vernier caliper, fifty division vernier caliper, etc.The vernier is a decade, and its length is 9 mm;The length of 20 divisions is 19 mm;The length of 50 divisions is 49 mm.The commonly used vernier calipers can be divided into three types according to their accuracy, namely 0.1mm, 0.05mm and 0.02mm.Vernier calipers with precision of 0.05mm and 0.02mm are common.[3]
Measuring pawl
There are two pairs of movable measuring jaws on the main ruler and vernier of the vernier caliper, which are internal measuring jaws and external measuring jaws.The inner measuring claw is usually used to measure the inner diameter, and the outer measuring claw is usually used to measure the length and outer diameter.[3]
Depth gauge
At the end of the main ruler is a feeler rod for measuring the hole depth.[3]
Caliper classification
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Classification by use
Common vernier caliper (general)
Height vernier caliper
The height vernier caliper (GB/T1214.3-1996) is a measuring tool used to measure the mutual position of workpiece surfaces and accurately draw lines.The specifications and measuring range of calipers are listed in the following table:[4]
Specification and measuring range of height vernier caliper (mm)
measuring range
Cursor reading value
0~200
0.02,0.05
0~300
0~500
0~1000
The height vernier calipers measuring height>200mm shall be equipped with inching device.[4]
Depth vernier caliper
Depth vernier calipers (GB/T1214.4-1996) are used to measure the depth dimensions of blind holes, step holes and grooves of parts.See the following table for the measurement range and main dimension parameters of caliper standard specifications:[5]
Measuring range and dimension parameters of depth vernier caliper standard specifications (mm)
measuring range
Length of measuring surface (L)
Width of measuring surface (B)
Cursor reading value
0～200，0～300
≧100
≧6
≧0.02,0.05
0~500
≧200
Tooth thickness vernier caliper
The type of tooth thickness vernier caliper (GB 6316-1996) is shown in the figure below, and its size parameters are shown in Table 1.[6]
Schematic diagram of tooth thickness vernier caliper
Table 1: Dimension parameters of tooth thickness vernier caliper (mm)
Analog measurement range
Cursor reading value
1～16，1～25
5～32 ，10～50
zero point zero two
Sort by Display
Vernier caliper with meter
Vernier caliper with watch is also called attached caliper, as shown in the following figure.It uses the rack drive gear to drive the pointer to display the value. The main ruler has a rough scale. Combined with the reading of the indicator, it is a vernier caliper, but it is faster and more accurate than the reading of the ordinary vernier caliper.[7]
Vernier caliper with meter
Vernier caliper without meter
Self locking vernier caliper
Classification by manufacturing materials
Stainless steel vernier caliper
Other steel vernier calipers
Classification by structure
Single side caliper
The single-sided caliper is equipped with internal and external measuring jaws, which can measure the internal and external dimensions, as shown in Figure 1.1.[8]
Double caliper
The upper measuring jaw of the double caliper is the external measuring jaw of the knife edge shape, and the lower measuring jaw is the internal and external measuring jaw, which can measure the internal and external dimensions, as shown in Figure 1.2.[8]
Three purpose caliper
The internal measuring jaw of the three use caliper is provided with a knife edge shape, which is used to measure the internal dimensions;The measuring surface of the external measuring jaw belt plane and the knife edge shape is used for measuring the external dimension;There is a depth gauge on the back of the ruler body to measure the depth and height, as shown in Figure 1.3.[8]
Vernier caliper classified by structure
Operation application
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working principle
Vernier caliper is an instrument commonly used in industry to measure length. It consists of a ruler body and a vernier that can slide on the ruler body.If viewed from the back, the cursor is a whole.There is a spring plate between the vernier and the ruler body. The elastic force of the spring plate makes the vernier and the ruler body close together.There is a fastening screw on the upper part of the vernier, which can fix the vernier at any position on the ruler body.Both the ruler body and the vernier are equipped with measuring jaws. The internal measuring jaws can be used to measure the width of the groove and the inner diameter of the pipe, and the external measuring jaws can be used to measure the thickness of the parts and the outer diameter of the pipe.The depth gauge is connected with the vernier to measure the depth of the groove and cylinder.There are scales on the ruler and vernier.Take the vernier caliper accurate to 0.1mm as an example, the minimum division on the ruler is 1mm, and there are 10 small equal divisions on the vernier with a total length of 9mm. Each division is 0.9mm, which is 0.1mm different from the minimum division on the main ruler.Zero of ruler body and vernier when measuring jaws are closedTick markIn alignment, the difference between their first scale line is 0.1mm, the difference between their second scale line is 0.2mm,..., and the difference between their tenth scale line is 1mm, that is, the tenth scale line of the vernier is exactly aligned with the 9mm scale line of the main ruler.When the linearity of the object measured between equivalent grippers is 0.1mm, the vernier shall move 0.1mm to the right.At this time, its first scale line is just aligned with the 1mm scale line of the ruler body.Similarly, when the fifth scale line of the vernier is aligned with the 5mm scale line of the ruler body, it means that there is a width of 0.5mm between the two measuring claws,..., and so on.When measuring a length greater than 1mm, the whole number of millimeters shall be read from the scale line opposite the vernier "0" line and the ruler body.
usage method
Wipe the measuring claw with a soft cloth to make it close together, and check whether the zero scale line of the vernier and the main ruler is aligned.If it is aligned, it can be measured: if it is not aligned, it should be recordedZero error: The zero scale line of the vernier on the right side of the zero scale line of the ruler body is called positive zero error, and the zero scale line on the left side of the ruler body is called negative zero error (this regulation method is consistent with the regulation of the number axis, and the right origin is positive, and the left origin is negative).During measurement, the right hand holds the ruler body, the thumb moves the vernier, and the left hand holds the object to be measured for the outer diameter (or inner diameter), so that the object to be measured is located between the external measuring jaws. When the object is closely attached to the measuring jaws, it can be read. When measuring the external dimension of the part, the connecting line of the two measuring surfaces of the caliper should be vertical to the measured surface, and should not be skewed.When measuring, gently shake the caliper and place it in the vertical position.Otherwise, the measurement result a will be larger than the actual dimension b;First, open the movable measuring claw of the caliper so that the measuring claw can freely clamp into the workpiece, and then attach the parts to the fixed measuring claw, and then move the ruler frame to make the movable measuring claw contact the parts with slight pressure.If the caliper is equipped with a inching device, tighten the fixing screw on the inching device, and then turn the adjusting nut to make the measuring claw contact the parts and read the size.Never adjust the two measuring jaws of the caliper to be close to or even less than the measured size, and forcibly clamp the caliper to the parts.Doing so will deform the measuring jaw or wear the measuring surface prematurely, which will cause the caliper to lose its due accuracy.
Fig. 3 Usage of vernier caliper
The above is an introduction to the vernier caliper, including its reading, use method and application. Since the vernier caliper is a relatively precise measuring tool, it has been widely used in industrial length measurement. With the development of science and technology and the continuous growth of the industry, the digitization of testing instruments is a common trend of current and future instruments,Moreover, the measurement efficiency of the workpiece will be required to be higher and higher.At present, the internal quality inspection method of the factory is to measure a data and record it on paper manually by the measuring personnel, or to measure it by one person and record it by another person. When analysis is needed, the operator will input it into the EXCEL form of the computer;The problem caused by this traditional measurement method is that the efficiency is low and the data is easy to remember wrongly.In view of this situation, a highly efficient method of using vernier calipers to measure the length has been promoted. Only by connecting our data acquisition instrument to the vernier calipers, the acquisition instrument will automatically obtain the measurement data from the vernier calipers, record, analyze and calculate, form corresponding graphs, and automatically judge the measurement results,This method really realizes the measurement of data, not only can reduce the error caused by manual measurement, but also can greatly improve the measurement efficiency.
Scope of application
As a common measuring tool, the vernier caliper can be specifically used in the following four aspects:
1) Measure the width of the workpiece;
2) Measure the outer diameter of the workpiece;
3) Measure the inner diameter of the workpiece;
4) Measure the depth of the workpiece.
reading
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When reading, first take the vernier zero scale line as the standard to read the millimeter integer on the ruler, that is, the integer part in millimeters.Then check which scale line on the vernier is aligned with the scale line on the ruler body. If the sixth scale line is aligned with the scale line on the ruler body, the decimal part is 0.6 mm (if there is no exactly aligned line, take the line closest to the alignment for reading).If there is zero error, the zero error shall be subtracted from the above result (zero error is negative, which is equivalent to adding zero error of the same size). The reading result is: L=integer part+decimal part - zero error to judge which scale line on the vernier is aligned with the scale line on the ruler body. The following methods can be used: select three adjacent lines, such as the line on the left is on the right of the corresponding line on the ruler body,The line on the right is to the left of the corresponding line on the ruler body, and the line in the middle can be regarded as being aligned L=align the front scale+align the nth scale line on the vernier with the scale line on the ruler body * (multiplied by)Graduation valueIf you need to measure several times to take the average value, you do not need to subtract it every timeZero error, just subtract zero error from the final result.
In Fig. 4, grid 7 is for alignment (direction not indicated by arrow).
A certain state of the 0.02 vernier caliper shown in Figure 4 is taken as an example for explanation.1. Read the scale to the left of the zero scale line of the secondary ruler on the main ruler, and this value is the integer part of the final reading.33mm as shown in the figure.2. There must be a scribe line on the auxiliary ruler that is aligned with the main ruler. Read on the auxiliary ruler that the number of divisions between the scribe line and the scale to the left of the zero scale line of the auxiliary ruler is 12 divisions. Multiply the precision of the vernier caliper by 0.02mm to get the decimal part of the final reading.Or directly read the reading of the scale on the auxiliary ruler, which is 0.24mm as shown in the figure.3. Add the integer and decimal parts to get a total size of 33.24mm.
accuracy
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The commonly used vernier calipers can be divided into three types according to their accuracy: 0.1mm, 0.05mm and 0.02mm.Vernier calipers with accuracy of 0.05 mm and 0.02 mm.Their working principle and use method are the same as that of vernier calipers with an accuracy of 0.1mm introduced in this paper.The vernier caliper with an accuracy of 0.05 mm has 20 equal divisions on the vernier, with a total length of 19 mm.When measuring, such as the 11th one on the vernierTick markIf it is aligned with the main ruler, the reading of the decimal part is 11/20mm=0.55mm. If the 12th graduation mark is aligned with the main ruler, the reading of the decimal part is 12/20mm=0.60mm.Generally, there are n equal divisions on the vernier, and their total length is equal to the total length of (n-1) equal divisions on the ruler. If the minimum division length on the vernier is x, and the minimum division length on the main ruler is y, then nx=(n-1) y, x=y - (y/n) The difference between the minimum divisions of the main ruler and the vernier is Δ x=y-x=y/ny/n, which is called the precision of the vernier caliper, and it determines the number of digits in the reading result.It can be seen from the formula that improving the measurement accuracy of vernier caliper is to increase the number of notches on the vernier or reduce the minimum scale value on the main ruler.Generally, y is 1mm, and n is taken as 10, 20, and 50, and the corresponding precision is 0.1, 0.05, and 0.02 mm.The accuracy of the mechanical vernier caliper with an accuracy of 0.02mm cannot be improved because of the limitation of its structural accuracy and the human eye's resolution to the alignment of the two scribed lines.
Custody matters
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Storage method
After using the vernier caliper, wipe it with cotton yarn.If it is not used for a long time, wipe it with grease or engine oil, close the two measuring jaws, tighten the fastening screws, and put it into the caliper box and cover it.The vernier caliper has four minimum reading values: 0.1 mm (10 equal divisions are marked on the vernier), 0.05 mm (20 equal divisions are marked on the vernier), 0.02 mm (50 equal divisions are marked on the vernier), and 0.01 mm (100 equal divisions are marked on the vernier).
matters needing attention
1. The vernier caliper is a relatively precise measuring tool, which should be handled with care and should not be collided or dropped underground.Do not use it to measure rough objects, so as to avoid damaging the measuring claw and putting it together with the cutting tool, so as not to scratch the surface of the vernier caliper. When not in use, it should be placed in a dry and neutral place, away from acid-base substances, to prevent corrosion.
Fig. 5 Multiple vernier calipers
2. Before measurement, the caliper shall be wiped clean, and the two measuring surfaces and the measuring edge of the caliper shall be checked to see whether they are straight and undamaged. When the two measuring jaws are closely fitted, there shall be no obvious gap. At the same time, the zero mark of the vernier and the main ruler shall be aligned with each other.This process is called checking the zero position of the vernier caliper.
3. When moving the ruler frame, it should move freely without too loose or too tight, let alone shaking.When fixing the ruler frame with fixing screws, the reading of the caliper shall not change.When moving the ruler frame, do not forget to loosen the fixing screws, and it should not be too loose to avoid falling.
4. When measuring parts with vernier caliper, it is not allowed to apply excessive pressure. The pressure used should make two measuring jaws just contact the surface of parts.If the measuring pressure is too large, not only will the measuring jaw be bent or worn, but also the measuring jaw will produce elastic deformation under the pressure, making the measured size inaccurate (the external size is smaller than the actual size, and the internal size is larger than the actual size).
5. When reading on the vernier caliper, hold the caliper horizontally in the direction of bright light, so that people's line of sight is as vertical as possible to the scribed surface of the caliper, so as to avoid reading errors due to the slant of the line of sight.
6. In order to obtain correct measurement results, you can measure several times more.That is, measure in different directions on the same section of the part.For longer parts, measurement shall be carried out at all parts of the whole length to ensure a relatively correct measurement result.
Routine maintenance
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1. Common fault repair of vernier caliper
Appearance repair:
Appearance requirements: the caliper surface shall be evenly coated, the scale mark shall be clear, the surface shall be transparent and clean, and there shall be no rust, bruise, burr, coating falling off and obvious scratch, no visible broken line or uneven thickness and other defects affecting the appearance quality.
Basic repair of appearance: first, clean the caliper with industrial gasoline or kerosene, and then remove the burr with fine oilstone, and then polish it in one direction by adding a small amount of kerosene with No. 0 fine sandpaper or No. 380 small sandpaper. The polished surface shall be as uniform as possible.
If there is serious corrosion on the polishing of the caliper scribed surface, the sandpaper can be cut into a narrow strip slightly smaller than the width of the main ruler, and the sandpaper can be pressed on the main ruler scribed surface by hand for polishing to prevent the occurrence of broken lines.
For chrome plated calipers, it is only necessary to clean them and remove the burrs with boron carbide oilstone. Generally, it is not necessary to polish them to prevent the chrome plating layer from being removed.
Repair of broken appearance measuring claw:
（1） The broken part is relatively short, so the measuring claw can be shortened and polished with a grinding wheel at the same time.
（2） If the broken part is longer or all of them are broken, the two measuring claws can be completely removed and repaired into a single measuring claw for use.
Repair of other obviously damaged parts of appearance:
During the use of calipers, due to accidents, the measuring jaws may be twisted, the traveling frame may be deformed or jammed, and the main ruler may be severely bent.When the measuring claw is twisted and the traveling frame is severely deformed, it can be clamped in a vice and corrected with a wooden hammer on the flat plate.
2. Requirements and repair for interaction of caliper parts:
Requirements: The ruler frame shall move along the ruler body smoothly without blocking or loosening.
Repair of inflexibility and shaking of ruler frame:
（1） The main ruler is bent and deformed: if the internal stress is not eliminated, it can be straightened on the clamping flat jaw pliers, or it can be straightened on the board with a hardwood hammer or a copper hammer with smooth surface.
（2） If the straightness and parallelism of the main ruler datum plane are not good, the main ruler datum plane should be longitudinally pushed and pulled on the working surface of the flat plate, or the measuring surface of the measuring claw can be roughly grinded to meet this requirement.
Repair of clearance between traveling frame, vernier and main ruler:
（1） Solder two thin copper sheets or steel sheets of appropriate thickness on both sides of the inner bottom surface of the traveling frame.
（2） For the caliper of the dead vernier, a metal bar with proper outer diameter can be placed on the vernier slope and squeezed with a vise
（3） For live vernier calipers, use a small file to trim the bottom surface of the vernier inward;You can also file down the surface on the travel frame that fits the vernier or grind off a layer on the surface.
Repair of inching device:
After the groove of the inching traveling frame is worn, there will be no travel. If the gap is small, you can narrow the groove in the vice and trim it with a small file.If the clearance is too large, nuts with appropriate length shall be prepared.
Repair and preparation of caliper spring:
When the measuring claw is closed for many times, the clearance is or is not, or the appearance is large or small, most of which is caused by the loss of elastic force of the spring plate. The spring plate should be replaced in time, and the spring plate should be adapted to the size of the ruler body. The frame should not be too tight or too loose.
Adjustment of caliper zero position:
（1） Adjust the method of pressing and activating the vernier.
（2） If the above method cannot be used after long-term use, the refitting method can be used to punch, tap, and drill the centering hole on the ruler frame, then the vernier can be installed and the zero position can be aligned.
3. Repair of the friction between the upper and lower planes of the measuring claw in the knife edge shape
First, find out which measuring claw is deformed, and then adjust it. Use a copper hammer or a wooden hammer to knock it to straighten the direction, but the impact force should not be too large to avoid greater deformation or breakage of the measuring claw.
4. Repair of flatness and parallelism of caliper measuring surface
（1） For manual grinding, clamp the caliper in the vise while grinding, and place the hand and grinder flat with even force without deflection.
When the grinding allowance of the measuring surface is large, rough grinding with an oilstone should be used first. This repair method is now widely used.
（3） The repair of parallelism is usually carried out at the same time as the repair of flatness.The grinder is the main tool for repairing the flatness and parallelism of calipers.
5. Repair of caliper indication error:
It shall be repaired according to the cause of error.Since the indication error comprehensively reflects the error of each part of the caliper, the indication error will generally meet the requirements after other parts are repaired and qualified.
6. Repair of flatness of sounding caliper:
matters needing attention
1. The vernier caliper is a relatively precise measuring tool, which should be handled with care and should not be collided or dropped underground.Do not use it to measure rough objects, so as to avoid damaging the measuring claw and putting it together with the cutting tool, so as not to scratch the surface of the vernier caliper. When not in use, it should be placed in a dry and neutral place, away from acid-base substances, to prevent corrosion.
2. Before measurement, the caliper shall be wiped clean, and the two measuring surfaces and the measuring edge of the caliper shall be checked to see whether they are straight and undamaged. When the two measuring jaws are closely fitted, there shall be no obvious gap. At the same time, the zero mark of the vernier and the main ruler shall be aligned with each other.This process is called checking the zero position of the vernier caliper.
3. When moving the ruler frame, it should move freely without too loose or too tight, let alone shaking.When fixing the ruler frame with fixing screws, the reading of the caliper shall not change.When moving the ruler frame, do not forget to loosen the fixing screws, and it should not be too loose to avoid falling.
4. When measuring the external dimension of parts: the connecting line of the two measuring surfaces of the caliper shall be perpendicular to the measured surface, and shall not be skewed.When measuring, gently shake the caliper and place it in the vertical position, as shown in Fig. 2-6.Otherwise, if the measuring claw is in the wrong position as shown in Figure 2-6, the measurement result a will be larger than the actual size b;First, open the movable measuring claw of the caliper so that the measuring claw can freely clamp into the workpiece, and then attach the parts to the fixed measuring claw, and then move the ruler frame to make the movable measuring claw contact the parts with slight pressure.If the caliper is equipped with a inching device, tighten the fixing screw on the inching device, and then turn the adjusting nut to make the measuring claw contact the parts and read the size.Never adjust the two measuring jaws of the caliper to be close to or even less than the measured size, and forcibly clamp the caliper to the parts.Doing so will deform the measuring jaw or wear the measuring surface prematurely, which will cause the caliper to lose its due accuracy.
5. When measuring parts with vernier caliper, it is not allowed to apply excessive pressure. The pressure used should make two measuring jaws just contact the surface of parts.If the measuring pressure is too large, not only will the measuring jaw be bent or worn, but also the measuring jaw will produce elastic deformation under the pressure, making the measured size inaccurate (the external size is smaller than the actual size, and the internal size is larger than the actual size).
6. When reading on the vernier caliper, hold the caliper horizontally in the direction of bright light, so that the line of sight of people is as vertical as possible to the scribed surface of the caliper, so as to avoid reading errors due to the slant of the line of sight.
7. In order to obtain correct measurement results, you can measure several times more.That is, measure in different directions on the same section of the part.For longer parts, measurement shall be carried out at all parts of the whole length to ensure a relatively correct measurement result.
Development trend
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Research and development of profiled vernier caliper
With the rapid development of the machinery manufacturing industry, various types of parts have a wide variety of shapes and structures. It is necessary to use matching measuring tools to detect the size of special parts, as shown in the following figure 2-1-17.[9]
