Electrical measuring instrument. Measuring Instruments - Technical Drawing

To determine the actual dimensions of parts, various measuring instruments are used, which are divided into universal, or scale, gauges, or scaleless, and precision.

Universal measuring instruments include: ruler, meter, caliper, depth gauge, micrometer, point gauge, protractor, etc.

To measure individual elements of parts that cannot be directly measured with conventional tools, auxiliary tools are used: calipers, bore gauges, thickness gauges, etc.

Measuring instruments are also divided into working and control. The working tool is intended for use in workshops, the control tool is for checking the working tool.

In addition, limit measuring instruments are used in serial production.

No matter how carefully the dimensions of a part are measured, the measurement results are not accurate enough, on the one hand, due to the imperfection of the measuring instruments, and on the other, depending on the measurement method. The deviation of the size obtained by measurement from the actual one is called the measurement accuracy, and the magnitude of this deviation is the degree of measurement accuracy. It is clear that the more accurately a part needs to be measured, the better the measuring tool and measurement methods must be. Therefore, depending on the accuracy of the measurements, measuring instruments are used accordingly, the most common of which are the following:

Steel ruler. It is manufactured in lengths from 150 to 500 mm (Fig. 207) and is used for measuring short lengths. The accuracy of measurement with a steel ruler reaches 0.25 -0.5 mm, depending on the skill of the measurer.

Meter. To measure long lengths, meters are used (Fig. 208), which are made of wood and steel. Wooden meters are only foldable and are usually used for rough measurements. Steel meters are made folding and in the form of a tape measure. Folding steel meters, like wooden ones, are used for rough measurements. The disadvantage of folding wooden and steel meters is that their joints become loose, resulting in large errors. Therefore, when measuring, it is better to use a tape measure. Tape measures are produced in one- and two-meter sizes. The accuracy of measurement with such meters is 0.25-0.5 mm, i.e. the same as when measuring with a steel ruler.

Calipers. A caliper is used for more accurate measurements of lengths and diameters (Fig. 209). It consists of a rod 1 with divisions in millimeters marked on it. At its left end there is a fixed jaw 2. The movable jaw 3 with frame 4, a vernier and a fastening screw are connected to the slider 6 by means of a micrometer screw 5. A knurled nut 7 is screwed onto the micrometer screw 5. The slider 6 is secured to the rod with screw 3.

In addition to what is described, there are also calipers with a depth gauge (Fig. 212).

With a caliper you can make measurements with an accuracy of 0.1 - 0.025 mm.

The vernier of a caliper is usually divided into 10 equal parts, with each division equal to 0.9 mm, therefore, 10 divisions of the vernier are equal to 9 divisions of the rod, i.e. 9 mm.

If the jaws of the caliper are moved closely, then the first stroke of the vernier, indicated by zero, coincides with the zero division of the rod, and the tenth division of the vernier coincides with its ninth division (Fig. 210). The difference between the first division of the rod and the first division of the vernier is 0.1 mm, for the second division - 0.2 mm, the third - 0.3 mm and the ninth - 0.9 mm. Therefore, if the movable jaw is moved to the right so that the first division of the vernier coincides with the first division of the rod, then 0.1 mm must be added to the whole number of millimeters to the left of the zero division of the vernier; if the second division coincides - 0.2 mm, the third - 0.3 mm, etc.

The accuracy of measurement with a caliper is equal to the ratio of one division of the rod to the number of divisions of the vernier. If the vernier is divided into 10 equal parts, then the measurement accuracy will be 0.1 mm. To set the caliper to a given size, move the movable jaw to the right until the zero division of the vernier coincides with the desired whole number of millimeters on the rod, and continue to move the jaw in the same direction until the required division on the vernier coincides with the nearest to it by division on the bar. The division of the vernier coinciding with any division of the rod will indicate the number of tenths of a millimeter. If, for example, you need to set the caliper to a size of 38.4 mm, then to do this, loosen the screw securing the frame and move it so that the zero division of the vernier coincides with the 38th division of the rod. If the caliper is equipped with a slider, then the vernier is set to a size of 0.4 mm by rotating the nut 7 until the fourth division of the vernier coincides with the nearest division of the rod (Fig. 211, a).

To read the size of a part measured with a caliper, it is necessary to note which division of the rod coincides with the zero division of the vernier. The coincident division will show the size of the measured element of the part. If the zero division of the vernier does not coincide with the whole number of divisions on the rod, then we note on the rod the nearest number to the left of the vernier zero and add to it the number of fractions of a millimeter on the vernier, which coincides with the nearest division of the rod.

In fig. 211, b shows a size of 45.3 mm according to the measured size of the part with a caliper.

In fig. 210 shows the measurement of the hole with the lower pair of jaws. In this case, to the size indicated by the caliper, it is necessary to add the thickness of the ends of the jaws, which is usually 8 or 10 mm.

As already mentioned, some calipers have a device for measuring depth, the so-called depth gauge (Fig. 212).

The depth gauge is attached to the frame of the movable jaw. The measured depth is calculated in the same way as when measuring the thickness or diameter of a part.

Micrometer. A micrometer (Fig. 213) is a more accurate measuring instrument than a caliper. Using a micrometer, you can take measurements with an accuracy of 0.01 mm.

The micrometer consists of a flat bracket 7, a heel 2, a spindle 3, a clamping ring 4, a tube with divisions 5, a sleeve 6 and a ratchet 7. A movable spindle 3 with a thread having a pitch of 0.5 mm is connected to the tube 5.

By rotating the sleeve you can set the spindle to the desired value. In the case when the spindle rests on the heel, i.e. when the distance between the heel and the end of the spindle is zero, the zero division of the vernier should be at the zero division of the tube. The ratchet head is connected to the ratchet inside the micrometer. The ratchet allows you to maintain a certain constant pressure of the spindle on the object being measured. If this pressure is exceeded, the head begins to slip, producing a cracking sound.

There are divisions on the tube and the beveled edge of the sleeve, the number of which on the sleeve is 50, and on the tube - according to the nominal size of the micrometer. The distance between the divisions on the tube is 0.5 mm. With one full revolution of the sleeve, the spindle moves 0.5 mm. Thus, when the sleeve is rotated by one division, the spindle will move by 0.01 mm.

Whole numbers and half millimeters are counted by divisions on the tube, and hundredths of a millimeter by divisions on the sleeve.

The sum of the readings on the tube and sleeve shows the distance between the heel and the end of the micrometer spindle.

In fig. 214, a shows the divisions of a micrometer set to a value equal to 14.31 mm, and in FIG. 214, b - by 12.38 mm.

When measuring with a micrometer, in order to avoid errors, it is necessary, from the moment the spindle approaches the part being measured, at a distance of approximately 1-2 mm, to rotate not the sleeve, but the ratchet head.

Micrometric shtihmas. Shtikhmas (Fig. 215) is used to measure the diameters of holes and is similar in design to the measuring device of a micrometer. Shgikhmas consists of a sleeve equipped with a tip with a spherical surface 2. The sleeve 7 includes a micrometric screw with a spherical end surface 5. The measurement results are counted by divisions on tube 3 (whole numbers and half millimeters) and by divisions of sleeve 4 (hundredths of a millimeter). Thus, the measurement result is the sum of two readings.

Like a micrometer, there are 50 divisions on the beveled edge of the sleeve, and millimeter divisions are marked on the 3-piece tube.

If sleeve 4 makes one full turn, then the screw with tip 5 will move by 0.5 mm, therefore, when the sleeve is turned by one division of its scale, i.e. by 1/50 of a turn, the screw will move by 0.01 mm.

In fig. 215 shtihmas shows that the distance between the ends of tips 2 and 5 is 82 mm. This value was obtained by adding two sizes: the nominal size of the gauge, equal to 63 mm (the nominal size of the gauge is taken to be the distance between the measuring ends 2 and 5 when the zero of the vernier coincides with the zero division of the tube) and the counting along the divisions of the tube and vernier. In this case, this value is 19 mm. Thus, 63+19=82 mm.

Micrometric depth gauge(Fig. 216) has the same device as a micrometer. The depth gauge consists of a crossbar 1, which has a measuring plane, rigidly attached to the stem 2. Inside the stem there is a screw with a measuring rod 3 and a retaining ring 4, a sleeve 5 and a ratchet 6. When measuring, the crossbar is pressed with the measuring plane to the part and the measurement is made as if measurements with a micrometer.

Goniometer. A goniometer is a device that is used to construct and measure the angles of parts. Protractors are manufactured with and without vernier. The most widely used in the USSR were protractors with verniers from the Krasny Instrumentalshchik and Caliber factories.

The goniometer of the "Red Toolmaker" plant (Fig. 217) consists of a half-disk 1 with a ruler 2 attached to it. The movable ruler 3, rigidly attached to the vernier 4, rotates around the O axis. To accurately set the vernier, use a micrometric screw 5. When measuring angles from 0 to 90°, put a square 6 on ruler 3. The measurement accuracy for this goniometer is within 2". A more advanced inclinometer is the inclinometer of the "Caliber" plant designed by D. S. Semenov (Fig. 218, a). This inclinometer consists of an arc 1 with a degree scale printed on it, along which plate 2 and a vernier 3 rigidly attached to it move. plate 2 has a holder 4, with which a square 5 with a ruler 6 is secured.

Plate 7 is rigidly connected to arc 1. The main degree scale is divided into 130°, however, by installing the measuring parts of the protractor in different positions, angles from 0 to 320° can be measured (Fig. 218, b). The measurement accuracy for goniometers of this design is 2".

To do, for example, an angle reading? using such a protractor, when the square occupies the position marked with the letter A (Fig. 218, a), it is necessary first of all to look between which divisions the zero division of the vernier is located. In fig. 218, and this division is located between numbers 33 and 34 of the main degree scale. After this, find on the right the division of the vernier, which coincides with one of the nearest divisions of the main scale. In this case, the division corresponding to 10" coincides. Therefore, the desired angle a is 33° 10". It is easy to see where the 10" comes from. The division corresponding to ten minutes-five to the right of the zero division of the vernier. Since the value of each division of the vernier is 2", then for five divisions this will be 2"X5=10".

Let, for example, you need to measure the angle p corresponding to the position of the square marked with the letter B. It is easy to see that the angle? is an obtuse angle consisting of the sum of angles: a and a right angle.

The value of angle a was determined earlier and is equal to 33° 10". Thus, angle? = a + 90° = 33°10" + 90° = 123°10".

Calipers and bore gauge(Fig. 219, a and b) are auxiliary tools and are used to measure quantities by transferring the size from the product to the measuring tool or vice versa.

A caliper is used to measure the external dimensions of parts, and a bore gauge measures the internal dimensions.

The caliper and bore gauge consist of two steel legs connected by a hinge.

The measurement accuracy of these instruments is low.

Reismas. A gauge (Fig. 220) is used when drawing parallel lines on parts, during marking work and measuring inaccessible parts of parts that cannot be measured with commonly used tools. The simplest surface gauge (Fig. 220, a) consists of a steel rod that moves along the groove of the rack and is then secured to the rack using a wing. The gauge stand is mounted on a stand. Work with a surface planer is carried out on a marking plate.

Shtangenreysmas(Fig. 220, b). For precise measurements and marking work, a height gauge with a vernier is used. A movable device with a scriber and a vernier moves along the ruler and is secured in the desired position with screws. Precise installation of the vernier is carried out in the same way as with a vernier caliper.

Thread gauges. To determine the thread pitch or the number of threads per 1" on threaded products, thread gauges are used (Fig. 221). Thread gauges are made for different thread systems and are a set of steel dies enclosed in a block.

Determining the thread pitch or the number of threads per 1" is done by selecting a comb profile corresponding to the angle of the thread profile. The comb will accurately indicate the thread pitch or the number of threads per 1" (Fig. 221, b).

To ensure that the found thread pitch or number of threads per 1" is correct, it is necessary to additionally measure the outer diameter of the thread using a caliper and compare the obtained data with the data of the corresponding thread standard. If the measurement data coincides, then the pitch or number of threads is determined correctly, in otherwise, the measurement must be repeated. When determining these values, it is necessary to carefully look at whether the thread gauge is selected correctly, i.e., whether the angle of the thread gauge profile corresponds to the profile of the threaded product. For more accurate measurements of threads, special thread micrometers, thread gauges, universal and instrumental microscopes are used.

In technology, under such a concept as measurement, implies a certain set of actions, the result of which is the determination of the numerical value that a certain physical quantity of an object has. Measurements are made using special technical means experimentally.

In an industry such as mechanical engineering, without carrying out various measurements it is absolutely impossible to get by. The quality of the products directly depends on the precision with which they are carried out. Regarding the values measurement accuracy, then at modern machine-building enterprises it is usually in the range from 0.001 millimeters to 0.1 millimeters.

In order to quickly and with minimal errors produce technical measurements, specialized devices and designs are used.

Metal ruler

This one measuring tool is perhaps the simplest in its design. With the help of metal rulers, the value of the measured quantity is determined directly.

Metal ruler

It should be noted that these measuring devices are also widely used for marking materials and parts. Modern industry manufactures them with measurement limits of 1000, 500, 300 and 150 millimeters, and either one or two scales are applied to them.

Calipers

This is widespread and actively used in technology (especially in mechanical engineering) measuring tool is much more complex than a metal ruler and provides much higher measurement accuracy. A caliper consists of such main parts as a ruler-bar, on the edge of which the main scale with equidistant divisions of 1 millimeter is applied, and a vernier - a reading device with an additional dashed scale.

Calipers

The division price of the verniers of modern calipers is either 0.1 or 0.05 millimeters, and as for the measurement limit, it reaches 2000 millimeters.

Calipers are used to measure both the external and internal dimensions of parts, as well as the depths of holes. In addition, they are used for various marking works.

Shtangenreysmas

This measuring tool is intended to measure the heights of parts and carry out their precise markings. The maximum measurement limit of height gauges is 2500 millimeters, and the division price of their verniers is 0.1 or 0.05 millimeters.

In most cases, this measuring tool is used when working on special cast iron plates. It is on them that it is installed along with those parts that need to be measured or marked.

In order to draw a line on the part to be marked using a height gauge, a special replaceable leg is used. The measuring tool itself moves directly along the surface of the slab.

Micrometer

Measuring tool This type is intended to make fairly accurate measurements of small linear dimensions. The maximum measurement limit of modern micrometers reaches 600 millimeters, and the accuracy is 0.01 millimeters.

Micrometer

Micrometers (as, indeed, all micrometric instruments) are equipped with special reading units based on a screw pair with a thread pitch of 0.5 millimeters. With its help, the longitudinal movement of the measuring screw is converted into circumferential movements made by the drum scale. It is on the basis of the angle of its rotation that the value of the measured size is determined.

Micrometric depth gauge

In essence, this measuring instrument is designed exactly the same as a micrometer. The only difference is that it is equipped not with a bracket, but with a base. It is in it that the so-called measuring stem is installed. In order to measure depth using a micrometric depth gauge, a special rod is used. It is installed on a screw and has a special shape. The measurement limit of modern micrometric depth gauges is up to 300 millimeters, and the division price of their verniers is 0.01 millimeters.

Dial indicator

This measuring instrument is a device where very small movements made by the measuring probe are converted into angular movements of the arrow. Dial indicators are used when it is necessary to determine with a significant degree of accuracy those deviations that a certain part has in its geometric shape in relation to the specified parameters. In addition, these devices are used to control the relative position of surfaces.

Mechanical goniometer

Goniometer

This measuring tool is designed to determine angle values, which in engineering are very often found in various assemblies, parts and structures. With the help of goniometers, measurements are made in angles, degrees and seconds, for which auxiliary elements and a bar scale are used.

Thread gauge

This measuring tool is used to accurately determine the thread pitch and profile. Structurally, it is a package of metal templates, each of which exactly repeats the configuration of a particular thread. Thread gauges that are designed to determine the pitch of metric threads are marked M60°, and those measuring devices that are intended to determine the number of threads per inch when measuring inch and cylindrical pipe threads are marked as D55.

Radius meter

This measuring tool is designed for measuring fillets and radii. It is a set of metal templates made in the form of plates from high-quality alloy steel. Moreover, they are all divided into those that are used to measure protrusions and those that are intended to measure depressions.

Gauge blocks

End gauges of length (often they are also called “ Ioganson tiles") are measures made in the form of a cylinder or parallelepiped, having strictly defined distances between the measuring planes. They can range from 0.5 millimeters to 1000 millimeters.

Modern production is unthinkable without measuring instruments; various types of them are used everywhere. With the help of monitoring the quality of products and various technological production processes. The measuring instrument is used in mechanical engineering, scientific laboratories, construction and in everyday life.

Measuring instruments are measuring instruments for providing results of measured physical quantities within a strict range. If a tool, in addition to physical parameters, allows you to determine whether the dimensions of an object are within acceptable values, then it is a control and measuring tool.

Measuring tools allow you to determine the geometric shape and size of an object, its density and elasticity, straightness and flatness.

Every measuring instrument has an error, because it is almost impossible to make an absolutely accurate measurement. The price of the instrument often depends on the value of this error. The smaller the error, the higher the cost of the product. But when using any tool, measurement error is possible. This happens due to improper use of the tool, its malfunction or contamination. Errors also occur when the measured object is contaminated or when the temperature regime is not observed. To reduce the likelihood of error and reduce the error, you must follow the operating rules of the measuring instrument.

According to GOST, measuring instruments are divided into 8 groups:

Smooth calibers
Threaded gauges
Complex and profile gauges
Measures and calibration tools
Vernier devices, tools and accessories
Mechanical devices, tools and accessories
Optomechanical and electromechanical devices, tools and accessories
Pneumatic instruments and accessories

The first 3 groups refer to special types of measuring instruments, the next 5 to the universal type. Universal instruments are used to measure various linear parameters of a product, regardless of its configuration.

They include the following widely used types of measuring instruments:

Vernier tools, the operation of which is based on the use of a vernier, which allows you to count fractional divisions (vernier calipers - used for high-precision measurements of external and internal measurements, as well as the depth of holes, vernier depth gauge - needed to measure the depth of holes with high accuracy, caliper gage - used for marking parts, depth of grooves and recesses).
A level that allows you to measure the deviation of structural parts horizontally and vertically.
, which allows you to measure small sizes with high accuracy.
A bore gauge measures the size of holes, grooves and other internal surfaces.
Squares and protractors that allow you to visualize and measure angles.
Feeler gauges designed to control gaps between surfaces.
Templates, depending on the type, used to measure the radius of a surface or the pitch of a thread profile.

You can also add the usual rulers and tape measures to the universal measuring tools.
Specialized measuring tools include various gauges that are designed to check the correct size and shape of products and help determine that the products will fit together and the assembly will be correct. Calibers allow you to measure one specific size of a product. They do not measure the actual size, but allow you to check that the product has not gone beyond the boundaries indicated in the drawing.

Trading house "Kvalitet" will provide you with a wide range of all types of measuring equipment.

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Helping a tool worker

Measuring instruments and tools

Measuring instruments and instruments are devices that are used to determine the dimensions of various parts.

According to their design characteristics, universal devices and tools are divided into line tools with a vernier - caliper tools and protractors; micrometric instruments - micrometers; lever-mechanical devices - indicators; optical-mechanical instruments - microscopes, etc.

Vernier tools are widely used in industry for measuring parts with an accuracy of 0.1; 0.05 and in rare cases 0.02 mm. The relatively high accuracy of vernier tools is achieved through a special device - a linear vernier.

The main parts of a vernier tool are a ruler-rod, on which a scale with millimeter divisions is printed, and a frame with a cutout, on the inclined edge of which a vernier (auxiliary) scale is made (Fig. 1). Depending on the number of vernier divisions, the actual dimensions of the part can be determined with an accuracy of 0.1-0.2 mm. For example, if a vernier scale (Fig. 1, a) 9 mm long is divided into 10 equal parts, then, therefore, each division of the vernier is equal to 9:10 = 0.9 mm, i.e. shorter than the division on the ruler by 1-0 .9 = 0.1 mm.

When the jaws of the tool are tightly moved, the zero stroke of the vernier coincides with the zero stroke of the rod, and the tenth stroke of the vernier coincides with the ninth stroke of the rod.

Rice. 1. Vernier device.

With this so-called zero setting of the vernier tool, the first division of the vernier will not reach the first division of the ruler-bar by 0.1 mm, the second by 0.2 mm, the third by 0.3 mm, etc. If you move the frame in this way, so that the first stroke of the vernier coincides with the first stroke of the rod, the gap between the jaws will be equal to 0.1 mm. If, for example, the sixth stroke of the vernier coincides with any stroke of the rod, the gap will be equal to 0.6 mm, etc.

To measure the actual size on a vernier tool, the number of whole millimeters must be taken on the rod scale to the zero line of the vernier, and the number of tenths of a millimeter - along the vernier, determining which line of the vernier coincides with the line of the main scale.

An extended vernier (Fig. 1) is more convenient than a simple one, as it has a longer scale - 19 mm. It is divided into 10 equal parts: 19: 10 = 1.9 mm, which is shorter than the division of the main scale by 0.1 mm.

Verniers with division values of 0.05 and 0.02 mm are designed similarly.

For vernier tools with an accuracy of 0.05 mm, the vernier scale is 19 mm and is divided into 20 divisions. Each division of the vernier is equal to 19:20 = 0.95 mm, i.e. shorter than the division of the main scale by 1-0.95 = 0.05 mm (Fig. 1, c).

Calipers are used for measuring external and internal dimensions, drawing arcs of circles and parallel lines when marking, for dividing circles and straight lines into parts and other operations.

The domestic industry produces the following types of calipers: ШЦ-1-with double-sided jaws for external and internal measurements and with a ruler for measuring depths with a vernier reading of 0.1 mm and with a measurement range of 0...125 mm; ШЦ-П - with a double-sided arrangement of jaws for measuring and marking with a vernier reading of 0.05 and 0.1 mm and with measurement limits of 0...200 and 0...320 mm; SHTsTP - with one-sided jaws with a vernier reading of 0.05 and 0.1 mm and with a measurement range of 0...500 mm; with a vernier reading of 0.1 mm and with measurement limits of 250...710, 320...1000, 500...1400 and 800...2000 mm.

A caliper with a measurement accuracy of 0.1 mm (Fig. 2, a) has a rod, which is a ruler with a main scale, and measuring jaws. A frame with two measuring jaws and a rod can be moved along the rod. A screw is used to secure the frame in the desired position. When the frame is moved to the right by the same amount, the measuring jaws 1 and 9, 2 and 3 move apart and the rod extends.

Long jaws are intended for measuring external dimensions, short ones - internal ones, and a rod - for measuring depths. The vernier of the caliper is marked on the frame.

A caliper with a measurement accuracy of 0.05 mm (Fig. 2,b) differs from the one discussed above in that it does not have a rod for measuring depths, but does have an installation device. For more precise adjustment, a device has been added here, consisting of a frame with a clamping screw and a micrometric nut screwed onto the screw. The latter is rigidly fixed in the engine and passes freely through the hole in the frame. If you secure the frame with a screw and then rotate the nut, the caliper engine will begin to move smoothly along the rod, providing a more accurate setting of the vernier. The screw is designed to secure the movable frame in the desired position.

Rice. 2. Calipers.

When determining internal dimensions with a caliper, it is necessary to add the width of the measuring jaws, which is usually indicated on them, to the dimensions obtained on the scale.

A depth gauge is designed to measure the heights and depths of various parts. It is built on the principle of a caliper, but the rod does not have jaws. The working (measuring) surfaces are the lower plane of the frame A (Fig. 3) and the end surface B of the rod. At the other end of the rod there is a third working surface B for measuring lengths in hard-to-reach places. The depth gauge consists of a rod, a micrometric device for precise aiming of the rod, a screw, a slider for micrometric feed, a screw, a nut, a vernier, a screw for clamping the frame, the main frame and a base.

Vernier depth gauges are manufactured with a vernier reading of 0.05 and 0.1 mm and with measurement limits of 0...200, 0...300, 0...400 and 0...500 mm.

The height gauge is used to measure heights, depths and to mark parts. Thickness gauges are manufactured with measurement limits of 0...200, 30...300, 40...500, 50...800 and 60...1000 mm and measurement accuracy of 0.1 and 0.05 mm.

The design of a caliper gage basically follows the design of a caliper and a caliper depth gauge. It has measuring surfaces, a base, a bracket clamp, a replacement leg, a bracket, a clamp clamp screw, a vernier, a micrometer nut, a feed screw, a rod, a main scale, a micrometer feed frame, a slide clamp screw, a frame and a frame clamp screw.

The measuring surfaces are the plane of the marking plate, on which markings and measurements are made, and two surfaces of the replaceable leg: the upper one for internal measurements and the lower one for external ones. Replaceable legs are installed in a clamp and secured with a screw. To measure heights and depths, instead of replaceable legs, pins are attached to the frame. A sharpened leg is used for marking.

The height gauge comes with interchangeable legs: one pointed for marking, one with two measuring surfaces and three pinned legs for measuring heights and depths. When measuring internal surfaces, it is necessary to add the thickness of the leg, which is indicated on it, to the readings of the height gauge.

Goniometers. To measure the angles of parts, two types of inclinometers with a vernier are widely used (GOST 53/8-66): UM - transporter for measuring external angles and UN - universal for measuring external and internal angles. In addition to mechanical inclinometers in accordance with GOST 11197-73, the industry produces optical ones of the UO type with a reading value of 1 - 5”.

The UM type goniometer, designed for measuring external angles from 0 to 180°, has a base in the form of a half-disk with divisions from 0 to 120° every degree, to which the rulers are rigidly connected. The latter is movable; it can be rotated around an axis together with the sector and vernier relative to the base and ruler. The vernier scale is constructed in the same way as that of vernier instruments. The presence of 30 divisions on it ensures a measurement accuracy of 2". Micrometer feed unit improves measurement accuracy.

Rice. 3. Vernier depth gauge.

Rice. 4. Height gauge.

Rice. 5. Goniometers.

A square can be attached to the movable ruler to measure angles from 0 to 90°. Angles over 90° are measured without a square, and 90° is added to the result. The sector is fixed relative to the base of the protractor using a stopper.

The UN type goniometer is used to measure external angles from 0 to 180° and internal angles from 40 to 180°. The protractor has a base with a degree scale rigidly connected to it by a ruler. The vernier scale is printed on a sector that moves along the base and is fixed in the required position with a stopper. A square is connected to the clamp sector, and a ruler is connected to the square. Micrometer feed unit improves measurement accuracy.

To measure angles from 0 to 50°, use a protractor, ruler and square; from 50 to 140° - instead of a square, install a ruler in the clamp; from 140 to 230° - a square is inserted into the clamp, and the second clamp and ruler are removed; Angles from 230 to 320° are measured with the clamp removed, i.e., without a square and ruler.

Increasing the accuracy of reading on the main scale of the protractor is ensured, as with vernier instruments, by using a line vernier. The principle of constructing a vernier in goniometers is the same as in aggangen tools.

Micrometric instruments. The design of micrometric instruments is based on the principle of a nut-screw screw pair. The rotational movement of, for example, a screw is associated simultaneously with its translational movement relative to the nut. With one full revolution of the screw, its longitudinal movement will be equal to the thread pitch. In all micrometric instruments, the thread pitch is S = 0.5 mm. When turning the screw one turn, its measuring surface will move by 0.5 mm.

The accuracy of micrometric instruments depends on the precision of the thread of the screw pair and the consistency of the pitch. They provide measurement accuracy up to 0.01 mm.

Micrometers for external measurements of sizes from 0 to 600 mm are produced in accordance with GOST 6507-78. The micrometer device is shown in Fig. 6. The heel and stem are pressed into the bracket. The micrometer screw is screwed into the micronut. The smooth bore of the stem ensures precise guidance of the microscrew. To eliminate the gap in the thread of the micropair, the thread of the micronut is made on its cut end, equipped with an external thread and a cone. An adjusting nut is screwed onto this thread, which is used to tighten the micronut until the microscrew moves in it without gaps. A drum is placed on the microscrew, secured with an installation cap, in which a blind hole is drilled for a spring and a tooth that rests on the toothed surface of the ratchet 10. The latter is adjusted so that when the measuring force increases above 900 gf, it does not rotate the screw, but turns. To secure the micrometer screw in a certain position, a locking device is provided, consisting of a sleeve and a screw. Micrometers with measurement limits greater than 25 mm are supplied with setting standards to set them to the lower measurement limit.

The micrometer scales are located on the outer surface of the stem and on the circumference of the drum bevel. On the stem there is a main scale, which is a longitudinal mark, along which (below and above) millimeter strokes are applied, with the upper strokes dividing the lower ones in half. Every fifth millimeter stroke of the main scale is elongated, and the corresponding number is placed next to it: 0, 5, 10, 15, etc.

Rice. 6. Micrometer.

The drum scale (or dial scale) is designed to count hundredths of divisions of the main scale and is divided into 50 equal parts. When the drum is rotated by one division along the circumference, i.e. by ‘/so part of a revolution, the measuring surface of the micrometer screw moves by ‘/so by the pitch of the screw thread, i.e. by 0.5:50 = 0.01 mm. Therefore, the price of each drum division is 0.01 mm.

When measuring with a micrometer, the part is placed between the measuring surfaces and, by rotating the ratchet, it is pressed against the heel with the spindle. After the ratchet begins to turn, making a cracking sound, the micrometer spindle is secured with a clamping ring and the readings are taken. A whole number of millimeters is counted on the lower scale of the stem, half a millimeter on the upper scale, and hundredths of a millimeter on the drum scale. The number of hundredths of a millimeter is counted according to the division of the drum scale, which coincides with the longitudinal line on the sleeve. For example, if it is clear on the micrometer scales that the edge of the drum has passed the seventh division, and the drum itself has rotated by 23 divisions in relation to the longitudinal line on the stem, then the full reading of the micrometer scales will be 7.23 mm.

Micrometric bore gauges are produced in accordance with GOST u 10-75 with measurement limits of 50...10,000 mm. The most widespread are bore gauges with measurement limits of 75...175 and 75...600 mm.

The bore gauge consists of a micrometer screw, a drum, a stem with a stopper, an adjusting nut and measuring tips. The nut protects the threads on the end of the stem from damage.

As with a micrometer for external measurements, the thread pitch of the internal micrometer screw is 0.5 mm. The maximum stroke of the micrometer screw is 13 mm. The maximum measurement limit of the main bore gauge head is 50…63 mm.

To increase the measurement limit, extensions are used - rods with dimensions from 500 to 3150 mm, enclosed in cylindrical tubes. To connect the extension to the bore gauge, an external thread is cut at one end of the extension, and an internal thread at the other.

The measurement with a micrometric bore gauge is carried out several times, turning it slightly around the circumference of the hole and looking for the largest size, as well as around an axis perpendicular to the axis of the hole, while determining the smallest size.

Micrometric depth gauges are manufactured in accordance with GOST 7470-78 with a measurement limit of 0...150 mm and a screw stroke of 25 mm. They are used to measure the depth of blind holes and cavities.

By using replaceable extensions, the measurement limits can be extended.

When measuring, the depth gauge is pressed with the measuring plane of the traverse to the surface of the part. To ensure a tight fit of the traverse to the part, the pressing force on the depth gauge should slightly exceed the measuring force.

Rice. 7. Micrometric bore gauge (a); extension cord (b) and micrometric depth gauge (c).

Lever-mechanical instruments are widely used in the tool industry because they are reliable in operation, have relatively high measurement accuracy and are universal. The principle of their operation is based on the use of a special transmission mechanism, which converts minor movements of the measuring rod into enlarged and easy-to-read movements of the arrows on the scale.

The most well-known types of lever-mechanical instruments include indicators, lever brackets, lever micrometers and minimeters.

Dial indicators are produced in accordance with GOST 577-68 with a division value of 0.01 mm and measurement limits from 0 to 10 mm depending on the standard size.

Rice. 8. Dial indicator.

The measuring rod of the indicator is made in the form of a toothed rack, which is meshed with a gear J2 with a number of teeth Z = 16. Arrows and an intermediate gear with a number of teeth Z-100 are fixed on the same axis with it. This wheel is meshed with a gear with the number of teeth Z = 10, on the axis of which there is an arrow-pointer indicating the magnitude of the linear movements of the measuring rod, in fractions of a millimeter, on a circular scale. For ease of use, the scale is connected to the rim of the indicator and together with it can be rotated to any angle. The wheel and spiral spring eliminate the backlash error of the transmission during reciprocating movements of the rod. Cylindrical spring I ensures contact of the tip of the rod with the controlled surface.

The indicator's gear ratio is selected in such a way that when the rod moves linearly by 1 mm, the indicator makes one full revolution. The circular scale is divided into 100 divisions. Consequently, the price of one division is 0.01 mm. The number of full turns of the pointer is shown by an arrow on the scale.

When performing measurements, indicators are installed in racks, on tripods or in special devices.

The indicator bracket is used to measure parts of the 6th and 7th qualifications. All lever clamps have a measuring range of 0...25 mm, provided by moving the adjustable heel. The division price of the reading device for staples with an upper measurement limit of up to 100 mm is 0.002 mm, and 125 and 150 mm is 0.005 mm. The measurement limits on the scale are respectively ±0.08 and ±0.15 mm.

The indicator bracket has a rigid body with two coaxial cylindrical holes, in one of which an adjustable measuring foot is installed, and in the other there is a movable foot, which is in constant contact with the measuring tip of the indicator. The measuring force is created by the combined action of the spring and the indicator spring. The heel can move freely within 50 mm for small staples and 100 mm for large staples. After setting the bracket to size, the position of the heel is fixed with a stopper and it is closed with a safety cap.

Rice. 9. Indicator bracket.

For ease of measurement, the bracket is equipped with a stop, which, when adjusting the bracket to size, is set so that the measurement line passes through the axis of the part being tested. The body has a handle with heat-insulating linings. The measuring rod is retracted by a lever

Lever micrometer. The structure of the tail part of a lever micrometer is the same as that of a conventional micrometer, with the only difference being that it does not have a ratchet.

Rice. 10. Lever micrometer.

The micrometer body contains a measuring contact, the movement of which to the left causes the lever, the gear sector and the gear wheel, on the axis of which the arrow is attached, to rotate. The spring serves to eliminate the gap in the engagement of the sector with the wheel and return the arrow and lever to their original position. To move the measuring contact to the left, there is a device consisting of a lever, a spring and a button. The spring is designed to create a normal measuring force. The stopper secures the micrometer screw in the required position.

The indicator mechanism is mounted in a bracket and closed with a lid, in the slot of which there is a scale with measurement limits from 0 to 0.020 mm in both directions. The value of each scale division is 0.002 mm.

Before starting measurements, it is necessary to check the zero point of the instrument. To do this, you need to connect the contacts so that the zero stroke of the drum aligns with the longitudinal stroke of the stem. The indication of the indicator scale arrow will give a zero point error, which must be taken into account with the opposite sign.

When measuring, placing the part between the contacts, rotate the drum until the indicator arrow goes beyond the scale in the range from 20 µm to 0. After this, by additionally rotating the drum, the nearest stroke of the drum’s circular scale is aligned with the longitudinal mark on the stem. The micrometer scale reading is algebraically (taking into account the sign) summed up with the indicator scale reading.

Optical-mechanical devices. To control cutting and measuring tools of complex shape, instrumental microscopes, optimeters and projectors are used.

Instrumental microscopes (GOST 8074-71) are designed for linear measurements along two rectangular coordinates, as well as for measuring angles, including thread elements. They are used to measure profile elements of templates, rake and back angles of spiral drills and countersinks, average diameter, profile angle and pitch of taps, helix angle of drills and reamers, taper angle of taps, etc.

Microscopes are produced in two types: MMI-fingered instrumental microscope with an inclined eyepiece head and BMI - large instrumental microscope.

An instrumental microscope has a base on which a movable table is located, consisting of three parts - lower, upper and rotating. The longitudinal movement of the lower part of the table is carried out by a micrometer head, and the transverse movement of the upper part of the table is carried out by the head. The angular movement of its rotating part by 5-6° to the right and left is made by a screw. Movements using the heads are limited to 25 mm. To increase the table travel in the longitudinal direction, it is moved to the right with a lever another 50 mm.

A column is installed on the base of the microscope, along which a bracket secured with a screw can move. The microscope tube is located on the bracket. The lens is installed in the lower part of the tube, and the microscope head, consisting of two eyepieces, is installed in the upper part. Under the eyepieces (Fig. 46.6), a glass plate with longitudinal and transverse strokes and a 360° circular degree scale rotates using a screw. Under the eyepiece there is a fixed plate with a scale on which 60 divisions are marked. Each division corresponds to one rotation of the movable plate. The eyepiece shows a crosshair of two mutually perpendicular dotted and two solid lines located at an angle of 60°. The crosshair is the boundary of the movement of the part when measuring linear dimensions and angles.

Rice. 11. Instrumental microscope.

Rough focus adjustment is achieved by moving the microscope bracket along the column, and more precise adjustment is achieved by using a screw. The final focus adjustment is made by rotating the eyepiece ring. The microscope column can be rotated by a small angle using screws. To measure rotation angles, there are divisions on the screws. The scales are illuminated by an electric lamp installed in the tube.

An optimometer - a measuring device with a division value of 0.001 mm - is used for linear measurements using the comparison method. In accordance with GOST 5045-75, vertical optimeters are produced - with a vertical axis for external measurements and horizontal - with a horizontal axis for external and internal measurements.

The operation of the optimometer is based on the laws of reflection and refraction of light. The optical diagram of the optimometer is shown in Fig. 12, a. Light from an external source, directed by a mirror and reflected by a glass plate, falls on the scale. The beam reflected from the scale is directed through a triangular prism into the objective and then reflected from the mirror in the opposite direction into the eyepiece, where an image of the reflected scale and arrow pointer is obtained. Since the mirror is connected to the measuring pin, a slight movement of the latter during measurement causes a slight rotation of the mirror, which causes the image of the reflected scale to shift relative to the fixed pointer. This displacement, observed in the eyepiece, makes it possible to take a reading.

The optimometer scale has 100 divisions on both sides of zero. The division value is 0.001 mm. Therefore, the measurement limit on the instrument scale is ±0.1 mm.

In tool production, a vertical optimeter is used (Fig. 12, b). It consists of a base with a stand, a bracket, a tube, a branch, a table and a clamping screw.

The parts are measured as follows. A block of gauge blocks of a given size is placed on the table and the optimometer is set to the zero position. Rough installation is done by moving the bracket by hand, and fine installation is done by lifting the table using a screw.

Rice. 12. Optical diagram of the optimometer (a) and vertical optimometer (b).

The table is positioned so that the measuring pin rests on the part, and the pointer visible in the eyepiece exactly coincides with the zero division of the scale. After this, the table is secured with a screw, the block of gauge blocks is removed, and the part is placed in its place.

If the dimensions of the part have some deviation from the size of the gauge block, this will cause movement of the measuring pin, corresponding deviations in the position of the mirror and raising or lowering the scale. To determine the size of the part, it is necessary to add or subtract the optimometer readings to the size of the block of gauge blocks.

The maximum height of a part measured on a vertical optimometer is 180 mm.

Any production involves the use of them. They are also necessary in everyday life: you must admit, it is difficult to do without the simplest measuring instruments during repairs, such as a ruler, tape measure, calipers, etc. Let's talk about what measuring instruments and instruments exist, what they are fundamental differences and where certain types are used.

General information and terms

A measuring device is a device with the help of which the value of a physical quantity is obtained in a given range, determined by the scale of the device. In addition, such a tool allows you to translate values, making them more understandable to the operator.

The control device is used to monitor the technological process. For example, this could be some kind of sensor installed in a heating furnace, air conditioner, heating equipment, and so on. Such a tool often determines properties. Currently, a wide variety of devices are produced, including both simple and complex ones. Some have found their application in one area, while others are used everywhere. To understand this issue in more detail, it is necessary to classify this tool.

Analog and digital

Instrumentation and instruments are divided into analog and digital. The second type is more popular, since various quantities, for example, current or voltage, are converted into numbers and displayed on the screen. This is very convenient and the only way to achieve high accuracy of readings. However, it is necessary to understand that any digital instrumentation includes an analog converter. The latter is a sensor that takes readings and sends the data to be converted into a digital code.

Analogue measuring and control instruments are simpler and more reliable, but at the same time less accurate. Moreover, they are mechanical and electronic. The latter differ in that they include amplifiers and value converters. They are preferable for a number of reasons.

Classification according to various criteria

Measuring instruments and instruments are usually divided into groups depending on the method of providing information. Thus, there are recording and display instruments. The first are characterized by the fact that they are able to record readings in memory. Self-recording devices are often used that print out data on their own. The second group is intended exclusively for real-time monitoring, that is, while taking readings, the operator must be near the device. Also, control and measuring instruments are classified according to:

direct action - one or more quantities are converted without comparison with the same quantity;
comparative - a measuring instrument designed to compare the measured value with an already known one.

We have already figured out what kinds of devices there are in terms of the form of presentation of readings (analog and digital). Measuring instruments and devices are also classified according to other parameters. For example, there are summing and integrating, stationary and switchboard, standardized and non-standardized devices.

Measuring locksmith tools

We encounter such devices most often. The accuracy of the work is important here, and since a mechanical tool is used (for the most part), it is possible to achieve an error of 0.1 to 0.005 mm. Any unacceptable error leads to the need for regrinding or even replacement of the part or the entire assembly. That is why, when fitting a shaft to a bushing, a mechanic uses more precise tools rather than rulers.

The most popular plumbing measuring equipment is a caliper. But even such a relatively accurate device does not guarantee a 100% result. This is why experienced locksmiths always take a large number of measurements, after which they select If more accurate readings are required, they use a micrometer. It allows measurements down to hundredths of millimeters. However, many people think that this instrument is capable of measuring down to microns, which is not entirely true. And it is unlikely that such precision will be required when carrying out simple plumbing work at home.

About protractors and probes

It is impossible not to talk about such a popular and effective tool as a protractor. From the name you can understand that it is used if you need to accurately measure the angles of parts. The device consists of a half-disk with a marked scale. It has a ruler with a movable sector on which a vernier scale is applied. A locking screw is used to secure the movable sector of the ruler to the half-disk. The measurement process itself is quite simple. First, you need to attach the part to be measured with one edge to the ruler. In this case, the ruler is shifted so that a uniform gap is formed between the edges of the part and the rulers. After this, the sector is secured with a locking screw. First of all, readings are taken from the main ruler, and then from the vernier.

Often a feeler gauge is used to measure the gap. It is a simple set of plates fixed at one point. Each plate has its own thickness, which we know. By installing more or fewer plates, you can measure the gap quite accurately. In principle, all these measuring instruments are manual, but they are quite effective and it is hardly possible to replace them. Now let's move on.

A little history

It should be noted when considering measuring instruments: their types are very diverse. We have already studied the basic instruments, but now I would like to talk about a little about other instruments. For example, an acetometer is used to measure strength. This device is capable of determining the amount of free acetic acid in a solution, and was invented by Otto and was used throughout the 19th and 20th centuries. The acetometer itself is similar to a thermometer and consists of a 30x15cm glass tube. There is also a special scale that allows you to determine the required parameter. However, today there are more advanced and accurate methods for determining the chemical composition of a liquid.

Barometers and ammeters

But almost every one of us is familiar with these tools from school, technical school or university. For example, a barometer is used to measure atmospheric pressure. Today liquid and mechanical barometers are used. The first ones can be called professional, since their design is somewhat more complex and the readings are more accurate. Weather stations use mercury barometers because they are the most accurate and reliable. Mechanical options are good for their simplicity and reliability, but they are gradually being replaced by digital devices.

Instruments and measuring instruments such as ammeters are also familiar to everyone. They are needed to measure current in amperes. The scale of modern instruments is graded in different ways: microamperes, kiloamperes, milliamperes, etc. They always try to connect ammeters in series: this is necessary to lower the resistance, which will increase the accuracy of the readings taken.

Conclusion

So we talked to you about what control and measuring tools are. As you can see, everyone is different from each other and has completely different scope of application. Some are used in meteorology, others in mechanical engineering, and still others in the chemical industry. Nevertheless, they have the same goal - to measure readings, record them and control quality. For this purpose it is advisable to use precise measuring instruments. But this parameter also makes the device more complex, and the measurement process depends on more factors.