The caliper got its name due to the main element of its body - the rod, but the compass we are used to is a little far from this tool in its structure. We will try to understand a subject full of mysteries with the help of this article, we will look at its structure and operating principle.
Vernier caliper design - main components and their purpose
The design of a caliper does not seem complicated from the outside, but its parts are so compact and optimally arranged that they make this device simple and easy to use. And it can do a lot, and the measurements that are performed with its help are very important in many areas of industry and construction. When using a caliper, we obtain the linear dimensions of objects, both external and internal. And the accuracy, which in some models reaches an enviable level, makes this simple tool increasingly in demand.
The purpose of a caliper is to measure lengths, diameters, depths, but let’s look at what provides this capability using the example of the simple type this device. The main unit is a ruler, which is called a rod, giving part of the name to the tool. The divisions on it are usually 1 mm, and the total length is usually 15 cm, but individual models can be longer. The ruler determines maximum size, which this instrument can measure. This means that the maximum length or diameter of the object should be no more than 15 cm.
At the end of the ruler there are sponges, or rather their halves, and the other halves are located on a movable frame, which moves along the ruler, measuring the size of the object being examined. There are internal and external sponges; in the former, the incisors face outward, in the latter, they face each other. Consequently, the first ones are inserted into the object and moved apart to fix the internal geometric parameter, and the second ones are moved apart widely and then come closer to fix the object under study among themselves. To accurately take the size or transfer it to another surface, the movable frame can be fixed with a special screw, which is located on it.
On the main ruler we can look at the integer value of the desired size, but the vernier scale, which is applied to the bottom of the frame so that it is exactly under the main marking of the ruler, will help to clarify the result. The vernier has ten divisions, each of which measures 1.9 mm, the entire scale is 1.9 cm long. These are the parameters of a regular household caliper; on other models this ratio changes. Having found a division of the vernier that coincides with any division of the main scale, you can refine the desired value to tenths of a millimeter. The use of a caliper is not limited to the internal and external dimensions; you can also mark the depth of the holes; for this there is a tail that extends from the ruler. This is a depth gauge scale.
Vernier calipers - classification and marking
The caliper measuring instrument can be of 3 types and about 8 standard sizes, at least according to domestic regulatory documents. Moreover, when purchasing any precision instrument, it is important to focus on the standards by which it is manufactured and calibrated. It is divided into types depending on the indicator of the measured value from which we take the required numbers. This there can be vernier (ShTs), dial (ShTsK) and digital (ShTsTs) calipers. In the first case, we will have to run our eyes over both scales, count the divisions and report the result. In the second case, we will see numbers on a mechanical scale with a moving arrow, but in the third case, we will be shown the finished result on the display.
Within these types, further subspecies can be divided depending on the design and length of the main line. For example, you can divide tools by the type of material from which they are made. An example of a hard alloy tool is ShTsT-I. There are differences in the structure of the sponges or additional accessories. Thus, ShTs-I and ShTs-III differ in the location of the jaws; in the first case it is bilateral, and in the second it is unilateral. But the ShTs-II has a micrometric feed frame, which will make marking easier if you need to transfer your measurements to another plane. There is no point in discussing the differences in standard sizes for a long time; one has only to say that the larger the ruler, the greater the error in the obtained values.
How to measure with a caliper - instructions for beginners
Most technically advanced people intuitively understand how to use a caliper, so we will briefly recall the main points.
How to measure with a caliper - step-by-step diagram
Step 1: Securing the Part
First check the tool for serviceability, to do this, reduce the jaws without the part to zero, look at the clearance, how correctly they are connected, and also look at the scale to see if the zeros on the two scales match. After a positive result, you can begin working with the part. It is most convenient to work in cases where the tool is in your right hand, and the part being measured is in your left, or is completely fixed somewhere. If you are left-handed, then the relationship is, of course, reversed. For measuring external size spread the jaws of the caliper, place an object between them and connect them. They should rest against the edges of the part being examined. If it is hard, you can lightly squeeze the lips for a firm touch. If the part is soft, do not do this, the results will be distorted.
The force is controlled simply; if you try to move the jaws relative to the object, then they should do it reluctantly, but if you also need force for this, then you have clearly squeezed.
It is more convenient to move the frame with your thumb right hand, holding the barbell with the rest. Check the position of the caliper relative to the object, whether there are any distortions (the jaws should be at the same distance from the edge of the object on both sides), it is better to raise the structure to eye level. To see more clearly, it is better to hold the object with your left hand in the plane behind the instrument, and not in front. Now you should carefully tighten the fastening screw with your index finger and thumb, while the rest should continue to hold the bar. When the value is fixed, the part can be put aside and proceed to study the next stage, how to measure the resulting number with a caliper.
Step 2: Remove the value
It is best to read readings at eye level. First of all, we write down the value of the main scale, i.e. integer. To do this, we look for the stroke on the main rod that is closest to the zero value of the vernier, this is an integer number of millimeters. You can remember it, or you can mark it somewhere on your draft. Now we are looking for a line on the vernier that is closest to its zero, but also exactly coincides with some division on the rod. Its serial number should be multiplied by the division value of the vernier used (usually 0.1 mm). If you are not sure that you know this value, look in the passport of this caliper.
Now it's a small matter, you just need to sum up these numbers, and the result is ready. For example, you had a value of 35 mm on the bar, and 4 more divisions were counted on the vernier, then the total value is 35.4 mm (3.54 cm). After work, the instrument is wiped (degreased), the jaws are slightly moved apart (by a couple of mm), the clamp is loosened and placed in the case. If you plan to store it for a long time, you can lubricate it against corrosion.
Determination of readings by vernier
To determine the readings of a caliper, it is necessary to add the values of its main and auxiliary scales.
- The number of whole millimeters is counted on the bar scale from left to right. The pointer is the zero stroke of the vernier.
- To count fractions of a millimeter, it is necessary to find the vernier stroke that most accurately matches one of the strokes of the main scale. After this, you need to multiply the serial number of the found vernier stroke (not counting zero) by the value of its scale division.
The measurement result is equal to the sum of two quantities: the number of whole millimeters and fractions of mm. If the zero line of the vernier exactly coincides with one of the lines of the main scale, the resulting size is expressed as an integer.
The figure above shows the readings of the ShTs-1 caliper. In the first case they are: 3 + 0.3 = 3.3 mm, and in the second - 36 + 0.8 = 36.8 mm.
The instrument scale with a division value of 0.05 mm is presented below. For example, two different indications are given. The first is 6 mm + 0.45 mm = 6.45 mm, the second is 1 mm + 0.65 mm = 1.65 mm.
Similar to the first example, you need to find the strokes of the vernier and the rod that exactly match each other. In the figure they are highlighted in green and black, respectively.
Mechanical caliper device
The design of a double-sided caliper with a depth gauge is shown in the figure. The measurement range of this tool is 0-150 mm. It can be used to measure both external and inner dimensions, hole depth accurate to 0.05 mm.
Essential elements
- Barbell.
- Frame.
- Sponges for external measurements.
- Sponges for internal measurements.
- Depth gauge ruler.
- Locking screw for fixing the frame.
- Vernier scale. Serves to count fractions of millimeters.
- Bar scale.
The jaws for internal measurements 4 are knife-shaped. Thanks to this, the hole size is determined on a scale without additional calculations. If the caliper jaws are stepped, as in the ShTs-2 device, then when measuring grooves and holes, their total thickness must be added to the readings obtained.
The reading value of the vernier may differ for different instrument models. So, for example, for ShTs-1 it is 0.1 mm, for ShTs-II it is 0.05 or 0.1 mm, and the accuracy of devices with a vernier reading value of 0.02 mm approaches the accuracy of micrometers. Design differences in the design of calipers can be expressed in the form of a moving frame, measurement ranges, for example: 0–125 mm, 0–500 mm, 500–1600 mm, 800–2000 mm, etc. The accuracy of measurements depends on various factors: the reading value on the vernier, work skills, and the good condition of the instrument.
The procedure for carrying out measurements, checking serviceability
Before work, check the technical condition of the caliper and, if necessary, adjust it. If the device has warped jaws, it cannot be used. Nicks, corrosion and scratches on working surfaces are also not allowed. It is necessary that the ends of the rod and the depth gauge ruler coincide when the jaws are aligned. The instrument scale must be clean and easily readable.
Measurement
- The caliper jaws are pressed tightly against the part with little force, without gaps or distortions.
- When determining the outer diameter of a cylinder (shaft, bolt, etc.), make sure that the plane of the frame is perpendicular to its axis.
- When measuring cylindrical holes, the jaws of the caliper are placed at diametrically opposite points, which can be found by focusing on the maximum scale readings. In this case, the plane of the frame must pass through the axis of the hole, i.e. Measurement along the chord or at an angle to the axis is not allowed.
- To measure the depth of a hole, a rod is placed at its edge perpendicular to the surface of the part. The depth gauge ruler is pushed all the way to the bottom using a movable frame.
- The resulting size is fixed with a locking screw and the readings are determined.
When working with a caliper, monitor the smooth movement of the frame. It should sit tightly on the bar without swaying, while moving without jerking with moderate force, which is regulated by the locking screw. It is necessary that when the jaws are aligned, the zero stroke of the vernier coincides with the zero stroke of the rod. Otherwise, reinstallation of the vernier is required, for which the screws securing it to the frame are loosened, the strokes are aligned and the screws are re-fastened.
Do-it-yourself apartment renovation always involves the need to take various measurements.
An ordinary ruler or tape measure cannot always provide the necessary accuracy, and in some cases they are simply impossible to use.
Vernier calipers are professional measuring instruments.
Our advice is designed to help the home craftsman choose it for performing many types of measurements and marking work in everyday life. Short review a wide range of industrial products will allow you to more accurately determine the required model based on its technical characteristics.
The optimal choice is possible based on taking into account:
- accuracy classes;
- measurement limits;
- ease of use;
- simplicity of design;
- cost.
Purpose
A caliper of any model is designed to perform high-precision measurements of three types of distances:
- external dimensions;
- indentations on internal cavities;
- recesses from the base surface.
A home craftsman may need a caliper when:
- choosing the drill diameter;
- at ;
- turning parts on a lathe;
- other repair work.
Design features
The caliper device is represented by three types of separate measuring devices, which have a common accuracy class and uniform measurement limits.
Their results are displayed on a common bar and vernier scale.
Components of a caliper
Structurally, the mechanism consists of:
- base element - rod;
- moving part - frames with additional devices.
Barbell
All details are placed on it. It is made of a flat metal strip with fixed jaws and a scale of millimeter divisions.
Frame
Composite design with internal grooves - the movable frame moves along the rod. It has its own jaws, vernier scale and locking mechanism.
The fixation unit consists of a force adjustment screw with a spring-loaded plate, which creates uniform pressure when the frame moves along the entire length of the rod.
The working edges of the jaws of the frames and the rod have an angular sharpening. To perform external measurements, it is created with limiting stops, and internal ones - along the entire length of the working edge.
Measuring scales
The length of the part being measured in mm is measured using the rod scale, and subsequent clarification of their proportions is carried out using the vernier. Its accuracy class in mm is:
- 0,02;
- 0,05;
The vernier scale can be applied directly to the body of the moving frame, as shown in the bottom photo, or attached with screws to perform precise calibration of the instrument - top photo.
How vernier and rod scales work
Let's look at the example of a caliper with an accuracy class of 0.1.
The price of one division of the bar located on top is exactly 1.0 mm, while that of the vernier is 1.9. Therefore, its ten lower divisions occupy 19 mm.
For all measurements, the zero position of the vernier scale, set opposite the upper divisions, is used as an indicator of the size of the part being measured. In the presented figure, it is located at the origin of the rod and indicates 0 mm of length.
During measurement, the movable frame moves along the rod, moving away from the beginning of the scale, and is fixed in a certain position, for example, as shown in the figure below.
The zero of the vernier scale has passed two millimeters along the rod. It indicates the whole part of the measured number - 2.0 mm. Of all the other nine marks of the moving frame, the fourth one came closest to the upper calibrated divisions. It shows the size of the fractional part - 0.4 mm.
All that remains is to fold them: 2.0 + 0.4 = 2.4 mm. We received the result of measuring a caliper in its accuracy class.
Design overview
All models of calipers can be divided into two types of measuring devices:
- mechanical with scales;
- digital with display.
Mechanical calipers
This type includes devices of the ShTs-1, ShTs-2, ShTs-3, ShTs-K brands.
Model ШЦ-1
The simplest and most common brand of caliper with a vernier scale type. Typical division value is 0.1 mm. But there are devices for 0.05 and 0.02.
Model ШЦ-2
The device differs from the previous one in the presence of an additional frame with a locking screw and an adjusting mechanism, as well as a special design of the jaws.
Their lower part allows you to measure both external and internal dimensions using two different working surfaces. The difference in reading between them in mm is marked directly on the body.
The protrusion line of the outer jaws is strictly parallel to the axis of the rod. This allows you to focus on them base surface of the part being measured: increased accuracy is created.
The upper jaws are pointed and perform two tasks:
Model ШЦ-3
The device completely repeats the design of the previous one, but it does not have the upper pair of marking and measuring jaws.
ShTs-2 and ShTs-3 are created with rods that make it possible to measure fairly extended parts.
Model ShTsK-1
The mechanism for counting fractions of mm is made of a mechanical device with a circular scale. These devices provide the most high class accuracy in its group: 0.02 or even 0.01 mm.
To move the movable frame when taking measurements, a rack and pinion transmission is used, controlled by rotation of the handle wheel. The head is also secured with a locking screw.
The disadvantages of this model include the need to maintain its rack and pinion rod mechanism and frame in constant cleanliness.
Calipers with digital display
One of the representatives of this class is the ShTsTs-1 model.
The additional letter “C” in the marking indicates the operation of the measuring device using digital technology. This makes it much easier to take the reading. ShTsTs-1 has the highest accuracy: class 0.01.
As with all similar devices, there are buttons for controlling various modes and standalone source power supply located in a special compartment.
When thinking about the quality of work of such meters, one should not forget about all the disadvantages inherent in electronic devices:
- sensitivity to external electromagnetic fields;
- limited battery life, which is also sharply reduced at cold temperatures;
- the need for protection from humidity and mechanical influences;
- increased cost.
When not in use, electronic devices are kept in special cases. To measure the dimensions of the parts, they are removed and then placed there again. They require more careful handling than simple mechanical analogues.
Checking serviceability and preparing for measurement
The measurement accuracy of any caliper depends on its technical condition. Examination metrological characteristics professional instruments are carried out by specialists from the relevant laboratories.
For home handyman such an operation is unnecessary. It is enough to check the calibration certificate when purchasing and then maintain your instrument in good condition.
However, the possibility of falls, impacts and other unforeseen events should be taken into account. To this end, it is important to periodically perform three simple rules functionality checks:
- inspection of external condition;
- checking the zero reading;
- assessment of the quality of measuring surfaces.
Visual inspection
They evaluate “by eye” the quality of the geometry of all parts, the cleanliness of surfaces, the need for lubrication of grooves with light oils, the condition of the scales and the ease of reading them. Check the ease of movement of moving parts.
Identified minor defects can be eliminated with your own hands.
Checking the zero reading
The movable frame is moved all the way to starting position and observe:
- setting both scales to zero;
- the location of the tenth division of the vernier at the 19 mm mark of the rod scale reading (for ShTs-1 accuracy class 0.1, as shown in the diagram above).
Assessment of the quality of measuring surfaces
The shifted jaws are placed towards the light source and the tightness of their fit is visually assessed. The picture above shows a similar test of one surface with a standard square.
Light rays will penetrate through defective cracks and indicate their location.
Pay attention to the position of the recess meter. When shifted, it should be in the same plane as the far end of the rod.
To do this, it is pulled out when installing the end of the rod on the reference plane and the measurement is taken on the reference scale. Should be 0.
Measurement techniques
It is important to understand: no caliper itself measures the part. It simply displays the position of the moving frame scale relative to the origin in a certain accuracy class. It is a person who takes measurements and quite often it is he who makes serious mistakes.
External distance measurements
The planes of the working surfaces of the caliper must be brought tightly to the part being measured.
Its axis should be perpendicular to them.
Tilt of the body onto the measurement surface until it stops with a bar or the use of special protrusions on the jaws helps eliminate measurement errors.
On long workpieces, the surface of the part should be parallel to the axis of the caliper rod.
Internal distance measurements
The jaws of the caliper should fit snugly against inner surface and be located in a perpendicular plane.
Definition of recesses
All the rules described above also apply here. The photo below shows one of the typical errors when the deviation of the meter from a plane parallel to the surface of the part being measured is violated.
To accurately determine the recess you need:
- ensure the correct support of the end of the rod in the reference plane;
- pull out the movable frame, firmly pressing the end of the pointer onto the remote surface;
- ensure its shortest distance to the measurement point with parallel orientation relative to the surface of the part;
- fix the locking screw;
- take the count correctly.
We hope that a short review and brief tips from the article will help you choose and buy a caliper of the model that best suits its characteristics. Now let’s give a photo of the ShTs-1 model, 160 cm long and 0.1 mm class, which has been working in the author’s arsenal of tools for the third decade.
Most often it is used for:
At one time there was a passion for wood turning and for them I did it myself. That's when calipers were used very often.
Then I had to replace the drill with a . But after that, interest in turning work somehow faded away, and the machine stood idle...
As personal practice has shown, an accuracy class of 0.1 mm is quite sufficient for doing household work, and if you follow the operating rules, then such a device works for a very long time and reliably.
Although some will find this clearly insufficient and will want to buy an electronic caliper ШЦЦ-1 with a class of 0.01 mm for their needs. Decide for yourself.
Ask questions in the comments, share the material you read with your friends on social networks.
It just so happened (at least for the author) that the accuracy of measurements is made: with a ruler up to centimeters and a half, with a caliper up to millimeters, but tenths and hundredths of a millimeter are “caught” exclusively with the help of a micrometer. What prevents you from using a caliper to measure tenths of a millimeter, since that is what it is designed for, it will be difficult to answer “offhand”. Often, even those who know the structure of this measuring instrument will be careful to indicate the size recorded with a caliper with an accuracy of tens - because the scale (vernier) “responsible” for determining tenths of a millimeter is small in nature. I admit that it is for this reason that some calipers began to be produced equipped with a dial scale and even equipped with an electronic display (electronic).
What prevents you from upgrading a caliper you already use and thereby bringing the accuracy of its measurements closer to those of a dial caliper and, for example, equipping it with a magnifying glass? He sat down at the computer and began to draw a device that had already visited his imagination.
Refinement scheme
I made a cross-sectional sketch with numbers:
- 1 - the caliper rod is indicated
- 2 - movable caliper frame
- 3 - holder frame, it is installed on a movable frame
- 4 - screw securing the frame to the frame
- 5 - screw securing the frame with a magnifying glass to the frame
- 6 - magnifying glass frame
- 7 - spring pressing the frame to the head of the fastening screw
- 8 - magnifying glass
In accordance with the finished sketch, I collected the most suitable components of the future holder “piecemeal”.
In a textolite cube (in the past, some part of the body of an electronic device, and in the future, a holder frame), using a file, I enlarged the existing groove to a size corresponding to the movable frame of the caliper and drilled a hole with a diameter of 3 mm in the center for the fastening screw.
On the side there is an M4 threaded hole for a screw securing the frame with a magnifying glass. With the completion of the manufacturing of the frame, labor-intensive operations requiring precision and careful fitting come to an end.
A frame was made from a piece of soft plastic (in addition to the existing one). Two holes are drilled in the plastic plate. The smaller one is for the frame fastening screw, the larger one is for the existing frame (into which it is threaded, which makes it possible to adjust the sharpness).
The device is assembled according to the drawing. I didn’t specially cut the thread in the additional frame; it was made by the thread of the old (metal) frame when screwing it in for the first time. For this purpose, a soft plastic plate was selected, and the hole was made 0.5 mm smaller than necessary. It is clearly visible that the vernier marks (the name of the scale for determining tenths of mm) have been increased to a size that is more comfortable for observation. This makes it possible to confidently determine the measured size with an accuracy of “ten”. And even more than that - now you can easily distinguish a wire with a size of 0.85 mm from 0.80 mm using measurement.
The procedure for taking caliper readings
- count the number of whole millimeters; to do this, find on the rod scale the stroke closest to the left to the zero stroke of the vernier;
- They count fractions of a millimeter, for this purpose they find a stroke on the vernier scale that is closest to the zero division and coincides with the stroke of the rod scale - its serial number will mean the number of tenths of a millimeter;
- add up the number of whole millimeters and fractions.
The device is easy to install and remove and can be used only when necessary. Author of the project - Babay iz Barnaula.
Discuss the article UPGRADE VERNIER CALIPS
As you will see from this article, modifying an electronic digital caliper is a very simple procedure, but it must be done carefully to avoid damaging the instrument. The design of the electronic caliper provides 4 special contacts. These contacts, for example, can be used to connect external source power supply, function control, etc.
The pin assignments are as follows (from left to right): negative terminal, data, clock and positive terminal.
To activate the hidden options of the electronic digital caliper, you need to connect pins 2 and 4 together.
Perhaps different electronic calipers have some differences, but in general their modification is carried out in the same way.
The first step in modification is to find the screws that hold the case together. On our caliper they are located under plastic sticker. Their location can be seen in the photograph.
After opening the plastic case containing the circuit board, display and several metal parts, you need to unscrew a few screws to remove printed circuit board.
Particular care should be taken when handling printed circuit board and display.
The display is connected to the printed circuit board via a conductive rubber gasket. Be careful not to disconnect the display from the board, as this will make it quite difficult to align the connections during reassembly. And if the position is incorrect, the display may spontaneously turn off and strange symbols may appear on it.
After removing the printed circuit board of the electronic caliper, we gain access to the necessary contacts.
Now you can solder 2 thin wires (the thinner the better). Solder one to pin number 2, and the other to pin number 4.
To close these terminals, it is best to use a micro button, for example from an old computer mouse. The pins of the button need to be bent at an angle of 90º (as in the picture) so that it fits tightly into the slot and therefore is held firmly in place.
After soldering the wires, assembling the electronic digital caliper is carried out in the reverse order. After assembly, soldered wires should stick out from the socket.
After that, solder the button and place it in the slot.
Since the button legs have been pre-bent, they spring the button and it is held firmly in place. This is what it looks like.
When we press the new button, we gain access to some modes that were not previously available.
When you press the button for the first time, the electronic caliper enters the fast reading mode (FT), when you press the “ZERO” button, we can freeze the measured value (H).
When you press the button again, the electronic caliper will enter the minimum value (MIN) mode. In this mode, the display shows the lowest measured value.
If you press the “ZERO” button again, we will again go into the mode of fixing the measured value (H).
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