Using a caliper. How to choose a caliper for a home craftsman

The main defects of a rod tool that can be eliminated during repair are errors in the divisions of the vernier, curvature of the guide rib of the rod, pitching and skew of the frame, non-parallelism of the measuring surfaces, their damage, wear of the base, etc.

Checking the correctness of the rod ribs and measuring planes of the jaws is carried out using blocks of gauge blocks, clamped between the measuring planes when moving the frame every 10 mm of the rod length. In any position of the frame on the rod, the force of pressure of the measuring planes on the block should be the same over the entire plane of the measure. If the contact of the measuring planes with any block is different for sharp and blunt jaws in different positions of the frame, this means that the rod is bent. If, at any position of the frame, the solution of sharp jaws is less than the solution of dull ones, or vice versa, then the caliper jaws are faulty.

To fix the rod, its working edge is checked for paint on a test plate, and the bulges are removed with a personal file or finishing. Then the second edge of the rod is made strictly parallel to the working edge, also using a file or finishing. After this, the measuring planes of the jaws are fine-tuned.

To fine-tune them, the caliper is secured in a vice with lead jaws (Fig. 177a). Finishing is carried out using a cast iron lap (Fig. 177, b). The lap is clamped between the jaws, for which the frame is brought close to the lap and the micrometric feed of the frame is fixed. Lapping should be without special effort move back and forth between the jaws.

Fig. 177.
Finishing the caliper jaws.

The skew of the jaws is not difficult to establish. To do this, it is enough to clamp the block of gauge blocks between the jaws and if one of the sides of the block moves away from one of the sides of the jaws, then the misalignment is established. The distortion of the working planes of the jaws in relation to the rod is corrected by grinding on a surface grinding machine. After grinding, both sharp and blunt jaws are polished with coarse GOI paste and polished with glass laps with a fine paste. The finishing of the jaws is considered complete if the lapping is carried out with the same force at both ends.

After finishing the jaws, check that the zero division of the rod coincides with the zero division of the vernier. To do this, the jaws move tightly and clamp the movable frame of the caliper. After making sure that there is no gap between the jaws, release the screws securing the frame to the vernier. Then move the frame with the vernier in one direction or another so that the first and last division of the vernier exactly coincides with the first and other corresponding division of the rod. Also pay attention to the fact that the second and third marks from the beginning of the vernier are located identically with the second and third marks from the end of the vernier in relation to the corresponding marks on the rod. After this, the screws are secured and, having once again checked the coincidence of the divisions, the installation of the vernier is considered complete. If, when installing the vernier, it is not possible to move it due to the gap in the holes for the screws, the holes are expanded using a needle file.

Breakage of the caliper jaws very often occurs. When correcting this defect, one of three decisions is made, shown in Fig. 178: shorten the length of the jaws (Fig. 178, a), remove one pair of jaws (Fig. 178.6) or make a cutout to insert a new jaw (Fig. 178, c). Sometimes a new one is welded in place of a broken jaw.

Fig. 178.
Repair and restoration of caliper jaws.

Correction of defects in lightweight calipers is carried out mainly by straightening with subsequent fine-tuning of the measuring planes. So, if even when the working surfaces of the jaws are worn out, the zero stroke of the vernier does not coincide with the zero stroke of the rod, then after fine-tuning the measuring planes this error will be even greater.

Therefore, it is corrected by straightening. The stationary sponge is placed on a hardened block secured in a vice, and it is struck at place a (Fig. 179) so that its nose moves down. Impacts are made on both sides of the caliper. The same is done with the sponge of the movable frame, hitting it in place b. The sharp ends of the jaws are straightened in places a and b.

Fig. 179.
Repair of a lightweight caliper (arrows show the locations of impacts during straightening).

After straightening, the measuring planes are cut down and adjusted until the divisions of the rod and the vernier coincide, and finally the nicks are cleaned and all planes are polished with fine sandpaper.

Correction of the gage base is carried out by lapping on a lapping plate using grinding powders.

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 industrial products of a large assortment will allow you to more accurately determine required model according to its technical characteristics.

The optimal choice is possible based on taking into account:

1. accuracy classes;
2. measurement limits;
3. ease of use;
4. simplicity of design;
5. cost.

Purpose

A caliper of any model is designed to perform high-precision measurements of three types of distances:

1. external dimensions;
2. indentations on internal cavities;
3. 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 vernier caliper device is represented by three types of separate measuring devices that have general class accuracy 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 bottom photo, or fastened 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 measuring device:

1. mechanical with scales;
2. 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 special design sponge

Their Bottom 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 with the 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 highest accuracy class in their 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 an autonomous power source 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 counterparts.

Checking serviceability and preparing for measurement

The measurement accuracy of any caliper depends on its technical condition. The metrological characteristics of professional instruments are checked 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:

1. inspection of external condition;
2. checking the zero reading;
3. 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 the initial position and observed:

• 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 the 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 mistakes, 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;
• provide it shortest distance to the measurement point in 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 device knowledgeable this measuring tool 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 by 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 screwed into a thread, 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

1. 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;
2. They count fractions of a millimeter; for this, on the vernier scale they find the stroke closest to the zero division and coinciding with the stroke of the rod scale - its serial number will mean the number of tenths of a millimeter;
3. 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

In production construction work or minor repairs often require measuring tools. Usually they are rulers or tape measures. But when measuring pipe diameter or hole depth, these tools are not suitable. For such purposes, more accurate measuring instruments- calipers.

This device is universal. It can be used to measure the external and internal dimensions of parts. Calipers have gained wide popularity in everyday life, as they have a simple design and are easy to use. Using such a device, you can quickly and easily take measurements with high accuracy.

Vernier caliper device

1 — Sponges for internal measurements
2 — Sponges for external measurements
3 - Clamping screw
4 - Movable frame
5 - Vernier
6 — Bar
7 — Bar scale
8 - Depth gauge

All instruments similar to calipers have a measuring rod, which is how the device gets its name. There is a main scale on the rod, which is necessary when measuring first.

A movable frame with a printed scale can move along the bar. The scale on the rod is called a vernier, which has more precise markings in fractional divisions. This provides increased measurement accuracy. The degree of accuracy of a caliper, depending on the design, can reach hundredths of a millimeter.

Calipers have two types of jaws:

• For measuring internal dimensions.
• For measuring external dimensions.

There is also another measuring element of the device, which is called a depth gauge. It can be used to measure hole depth and other dimensions.

Digital calipers are designed in a similar way. However, instead of a vernier, a digital scale is used, which increases the ease of use and measurement accuracy of the device.

1 - Clamping screw
2 - Battery
3 - Roller length change
4 - Reset
5 - On/Off
6 - Switch mm/inches

Like all measuring instruments, digital instruments are equipped with a scale with a division value of 0.01 mm. Permissible error is considered to be a deviation of the measurement result by less than or big side on 10%. In industry, all measuring instruments are subject to metrological control every six months.

The retail chain sells calipers packaged in a case. When purchasing a tool, it is recommended to inspect the measuring jaws. They should be smooth, and there should be no gap when they are compressed.

The vernier scale should be in the zero position when the jaws are closed. The lines marking the scale divisions along the vernier must be clearly marked. The kit of the device must include a passport with a mark on the accuracy verification performed.

Types and features

Main types of calipers:

There are several subtypes of different calipers depending on the size, design features and operating principle. Below we consider the main types of such measuring instruments.

ШЦ-I

This is the simplest and most popular model of the device, which is widely used in industrial production. It is called “Columbian” after the name of the manufacturer that produced the instrument in war time(Columbus).

The device can measure internal and external dimensions and depth. The measurement interval is from 0 to 150 mm. The measurement accuracy reaches 0.02 mm.

SCC-I

This digital measuring tool model has a similar design to the classic caliper. Measurement interval 0-150 mm. One of its advantages can be called more high accuracy when measuring due to the presence of a digital indicator.

The convenience of using such a digital device is that the indicator can be reset to zero at any measurement point. You can also easily switch from metric to inch with just one button.

When purchasing a digital model, you need to pay attention to the presence of zero readings when the jaws are closed, and also when the locking screw is tightened, the numbers on the display should not jump.

ShTsK-I

In this design of the caliper there is a rotary indicator with a round scale, the division value of which is 0.02 mm. These calipers are convenient to use for frequent measurements in production. The indicator arrow is clearly visible for quick control of the result; it does not have jumps, unlike digital models. This device is especially convenient to use in the department technical control for measurements of similar standard sizes.

ШЦ-II

Such rulers are used for measuring internal and external dimensions, as well as for marking parts before processing. Therefore, their jaws have attachments made of hard alloy to protect them from rapid wear. The measurement interval of the ShTs-II series of devices is in the range of 0-250 mm and the measurement accuracy is 0.02 mm.

ШЦ-IIIand SCC-III

Large parts are most often measured with this model of instrument, since its measurement accuracy is higher than other models and is 0.02 mm for mechanical instruments, and 0.01 mm for digital instruments.

The largest dimension to measure is 500mm. The jaws in such models are directed downwards and can be up to 300 mm long. This makes it possible to measure parts over a wide range.

Special purpose calipers

Let us briefly consider several specialized models of calipers designed for special types works Such devices appear quite rarely in the retail chain.

• SHTSCT– used for measuring pipes, it is called a pipe caliper.
• SHTSTSV— for measuring internal dimensions, has a digital display.
• SHTSCN– similar to the previous device, used to measure external dimensions.
• SHCCU— a universal digital meter, the kit includes a set of attachments for hard-to-reach measurements: center-to-center distances, pipe walls, external and internal dimensions, etc.
• SHCD– a device for measuring the thickness of brake discs and parts with various protrusions.
• SHTSCP— Vernier calipers are used to measure the tread depth of car tires.
• SHTSTM– calipers designed specifically for measuring center-to-center distances.

Rules for using calipers

• Check the tool. To do this, bring the caliper jaws together and check the accuracy of their closure for the presence of clearance between them.
• Take the tool in right hand, and the measured part in the left hand.
• For measuring external size parts, it is necessary to separate the lower jaws of the tool and place the part being tested between them. You should be careful when doing this, as the edges of the jaws are sharp and you can get injured if you handle the tool carelessly.
• Squeeze the jaws of the caliper until they come into contact with the part. If the material used to make the part has a soft structure, then strong compression of the jaws will lead to inaccurate measurements. Therefore, the jaws must be squeezed carefully, only until they come into contact with the surface of the part. To move the caliper frame, use thumb hands.
• Check the position of the jaws relative to the part. They must be at an equal distance from the edges of the part; tool distortions are not allowed.
• Secure the screw intended for clamping the movable frame. This allows you to maintain the position of the frame for accurate measurement results. It is advisable to tighten the screw with your thumb and forefinger, while at the same time holding the instrument in one position with the same hand so as not to move it to ensure measurement accuracy.
• Put the part aside, and take the fixed caliper without the part to take the measurement results.
• The instrument reading stage is very important, since inaccuracy in measurement can lead to serious consequences in production.

Place the caliper directly in front of your eyes.

1 — Bar scale
2 - 21 divisions
3 — Vernier scale

The figure shows the measurement procedure. On the left are jaws for external measurements with the part being measured, and on the right are scales: vernier and main. Their divisions will determine the measurement result.
First you need to count the number of whole millimeters. To do this, you need to find the division on the rod scale that is closest to the vernier zero. This division is indicated by the first upper red arrow. In our case, this value is 13 mm. This value must be remembered or written down.
Next you need to calculate fractions of a millimeter. To do this, you need to find a division on the vernier scale that coincides with the division on the rod scale. This division in the figure is shown by the second red arrow.
Next, you need to determine the division number in order, for our case it turns out to be 21.
Then you need to multiply this number by the value of the vernier scale division. In our example, the division value is 0.01 mm.
Now it is necessary to calculate the exact value of the measurement determined by the caliper. To do this, you need to add the whole number with fractions of a millimeter. The result is 13.21 mm.

• When finished using the tool, clean it, loosen the screw, close the jaws and put it in the case. If the instrument will be stored for a long time, it is recommended to treat it with an anti-corrosion solution.

If you have a dial or digital caliper, the measurement process becomes much easier, since you don’t need to calculate anything, the finished result will be visible on the display or dial.