Control and measuring instrument. Measuring hand tools How to properly maintain a measuring tool

A measuring instrument is a broad concept that denotes a class of devices that allow one to establish quantitative relationships of any parameters in comparison with a standard. In scientific activities, measurements are associated with determining the numerical characteristics of a wide variety of quantities: mass, induction, spectral.

In production, measuring tools and instruments are used to compare the predominantly geometric characteristics of a manufactured product with a given sample.

Accuracy and error

The main characteristic of measuring instruments and devices is accuracy. This concept refers to the amount of deviation from the true values ​​that arises as a result of measurement error. Different industries have different accuracy requirements. In woodworking and the production of building metal structures, an error of 1 mm is allowed, in metalworking operations - 0.1-0.05 mm, in precision engineering, the deviation can be 0 microns.

The accuracy of measurements is affected by the physical condition of the instrument. To determine wear, the measuring tool is checked - an operation to identify the degree of non-compliance of the measuring instruments with the specified characteristics. The main verification methods that are used to assess the performance of a mechanical tool are methods of direct comparison and direct measurements. In these cases, control and measuring instruments for marking are used for verification. These are devices of similar design, the parameters of which have been verified.

The main requirement for accuracy is to use measurements to give the mating parts the shape that is needed for their constructive interaction. The accuracy of measuring the smoothness of races and balls in bearings must be at a level to ensure high rotation speeds. When assembling a frame, the wooden parts of which should not move relative to each other, it is enough to ensure that they fit tightly.

The physical properties of the processed materials and their ability to change parameters depending on climatic conditions are of great importance for accuracy. Hence the conclusion: carpenter's tools, the measuring devices of a turner, a mechanic and a carpenter have different accuracy.

Classes, types, types of measuring instruments

First of all, all meters are classified according to the nature of their use. The most extensive class is the universal tool. This includes all devices for general use - those that are used in all industries and fields of activity.

General purpose meters are interchangeable and are issued without restrictions. The devices are often in the personal use of the craftsmen. A special tool belongs to individual industries and technological complexes. This class includes instruments used to measure specific parameters: surface smoothness, its hardness. Can be used to determine the parameters of individual products, such as gears. The nature of the use and storage of such funds, as a rule, is of a sensitive nature. For example, in rocket science, measuring instruments are checked daily by metrologists before they are issued.

In addition, there are:

• measuring and marking tools;
• hand and mechanical tools;
• metal, plastic and wood.

There are types of measuring instruments based on technological characteristics, for example, metalworking tools. This type includes the following types: calipers, micrometer, probes, calibration and marking rulers. Another type is carpentry tools.

The most popular types here are represented by a square, a planer, a thickness planer, and a caliper. Construction tools are tape measures, spirit levels, folding meters. Many devices are universal: they are used by masters of all engineering professions.

Meters used in metalworking

The most common universal measuring instrument is a ruler. The marking ruler is used by all specialists, regardless of their profile. A more specific set of measuring devices include straight edges. They are used to identify deviations of products along the plane. The magnitude of deviations is determined using calibrated probes - metal plates, the thickness of which ranges from 0.01 mm to several mm. Using special rulers, modelers determine the shrinkage size of hot ingots.

In the metalworking industry, two main types of instruments are used to measure linear characteristics:

• line instrument with vernier;
• screw type micrometer instrument.

Line instruments with vernier scales

The most popular representative of this class is the caliper. Structurally, the device is a rod made of hard alloy, which ends at one end with a sponge. On the surface of the rod there is a metric scale with a division value of 1 mm. A carriage moves along the groove of the rod: one end ends with a sponge. There is a bar scale on the carriage. Several types of verniers are used in industry:

• by 9 or 19 divisions - with an accuracy of 0.1 mm;
• by 39 divisions - with an accuracy of 0.05 mm.

A variety of vernier tools are meters with a dial indicator and devices with digital electronic sensors. In the first case, translational motion is converted into rotational motion by a system of gears with a slider. The accuracy of such a caliper increases to 0.02 mm. Electronic devices provide measurements with an accuracy of 0.01 mm. Shtangelreismass is a subtype of caliper made on a stationary stand. This hand-held device is designed for measuring and marking.

A micrometer instrument is a pair of screws with a fine thread, to which a clamp with a precision heel is attached. The forward movement of the screw is communicated using two rotating mechanisms: a drum and a ratchet. Measurement procedure:

• the part to be measured is installed between the screw and the heel;
• the drum is turned until the part comes into contact on both sides with the screw and the heel;
• Use a ratchet to turn the mechanism until the part is completely secured.

Readings are taken from three scales. The first is located on the bottom of the stem: it shows the approximate size of the part in millimeters. On the scale above you can see whether the error of the first measurement is more or less than half a millimeter. The exact value of hundredths of a millimeter is marked on the drum scale. The final size of the part is equal to the sum of the data from all scales.

Products produced by the engineering industry - machines, machines, instruments, tools and fixtures - consist of parts of various shapes and sizes. In the manufacture of these parts, control and measuring tools are used. The process of measurement consists of comparing the measured quantity with another homogeneous quantity, which is a generally accepted unit of measurement.

Inspection and measuring instruments can be divided into three main groups: length measures, universal instruments, gauges and indicators.

Measures are instruments that reproduce units of measurement or its multiples. Line length measures - scale rulers, folding meters, tape measures - reproduce linear dimensions within certain limits.

1.1. Plane-parallel gauge blocks

Plane-parallel gauge blocks are a set of precise steel gauges in the shape of a rectangular parallelepiped with two mutually parallel measuring surfaces, the distance between which determines their size (Figure 1, a).

The end blocks are made from high-quality chromium steel, undergo a complex heat treatment cycle with hardening to a hardness of HRC 62...64 and are carefully processed by grinding and finishing. The nominal size between the measuring surfaces of plane-parallel gauge blocks is maintained with an accuracy of 0.0001 mm, and the roughness of the working surfaces is maintained according to class 13. Thanks to this, the end blocks have the ability to rub against each other, which makes it possible to make non-scattering blocks from several end blocks (Figure 1, b).

Depending on the manufacturing accuracy, gauge blocks are divided into accuracy classes: 0, 1, 2 and 3. The most accurate is class 0. End measures are completed in sets No. 1 (of 87 measures), No. 2 (of 42 measures), No. 3 (of 116 measures) and other numbers consisting of end measures selected in such a way that any required size can be made with an interval of 0.001 mm. When compiling a block of the required size, first take a gauge measure, which has a size that includes thousandths of a millimeter. The size of this gauge block is subtracted from the required block size. Then take a gauge measure of size including the required hundredths of a millimeter, and its size is subtracted from the remainder obtained after the first subtraction; then the size of the next end blocks is determined in the same way. It is necessary to strive to ensure that the block consists of as few end measures as possible. Figure 1, c, d, e shows examples of various uses of a set of plane-parallel gauge blocks.

With the help of various devices, gauge blocks can be used to control the size of a precise part, template or gauge, to install various measuring tools and devices using the relative method of measuring size, for precise marking.

1.2 Probes

Probes (Figure 2) are a set of precisely machined steel plates with a thickness of 0.02 to 1 mm and a length of 100 or 200 mm. Feeler gauges are used to check the size of the gaps between mating parts.

They produce four sets of probes, differing from each other in the number of plates and their thickness. The thickness of the plates in the set is indicated on each of them and alternates in set No. 1 every 0.01 mm;

set No. 2 has 17 plates, first every 0.01 mm, and then every 0.05 mm;

set No. 3 has 10 plates ranging in thickness from 0.55 to 1 mm, and set No. 4 has 10 plates ranging in size from 0.1 to 1 mm.

To determine the size of the gap, the plates are introduced into the gap alternately (one at a time or two or three at a time) without force until their total thickness corresponds to the gap.

1.3 Rulers

A ruler (Figure 3, a) is a measuring tool made of sheet tool steel. Divisions in the form of strokes are applied to the ruler. Metal rulers are made with scale lengths of 100, 150, 200, 300, 500, 750 and 1000 mm.

A folding meter is a ruler consisting of ten plates connected with rivets. The protrusions on the plates ensure a stable position of the meter when unfolded.

Roulette (Figure 3,b) is a long steel tape with divisions printed on it. Tape measures with a division value of 1 mm along the entire length of the measuring tape are made with a length of 1; 2 5; 10; 20; 30 and 50 m.

1.4 Vernier tools

For more accurate measurement of linear dimensions, calipers, height gauges, height gauges, etc. are used.

Vernier tools include measuring instruments with a linear vernier: calipers, height gauges and depth gauges.

These instruments are equipped with linear scales, the reading of which is carried out using an additional scale - a vernier.

The ShTs-1 caliper (Figure 4, a) is widely used for measuring external and internal dimensions. The reading value on the vernier is 0.1 mm.

The height gauge (Figure 5) is a measuring and marking tool. The height gauge has a vertical ruler 2, fixed in a massive base 1. A slider with a vernier 4 moves along the ruler, secured to the ruler 2 with a screw 5. A replaceable leg is attached to the slider foot - a scriber 10 with a tip 11 made of a carbide plate.

The slider 6 is connected to the slide with a micrometric screw 8 and is installed on a vertical ruler with a locking screw 7.

Vernier is used to count the fractional part of the division interval of the main scale.

Vernier (Figure 6) is characterized by the reading value A and module y, determining the length of the vernier relative to the main scale.

Quantities A And at can be determined by the formulas:

where – interval of division of the main scale – price of division of the scale (usually = 1mm); – number of divisions on the vernier; – vernier length.

Vernier tools are manufactured with a reading value A, equal to 0.05 and 0.1 mm, and with module y. equal to 1, 2 and less often 5.

1.5 Micrometers

Micrometers (Figure 7) are designed to measure the external dimensions of a part. The micrometer has a bracket, on one side of which a fixed heel 2 is installed. The second side of the bracket has a complex design. The main measuring mechanism of the micrometer consists of a nut 5 and a spindle 3 screwed into it. The spindle is pressed into drum 6. When drum 6 rotates, the spindle rotates. To determine the exact size, the ratchet 7, when rotating, transfers pressure to the micrometer screw and to the spindle 3. The spindle 3, resting against the surface of the part being measured, will stop the rotation of the drum 6. The micrometer allows you to measure dimensions with an accuracy of 10 microns. Micrometers are produced with measurement limits of 0...25, 25...50, 50...75, etc. up to 275...300 mm.

1.6 Straightness and flatness controls

The most common means of checking straightness are straight edges, which are available in several types.

Pattern rulers. Three types of pattern rulers are made: straight with a double-sided bevel (Figure 8, A), triangular (Figure 8, b) and tetrahedral (Figure 8, V). Straightness is checked using pattern rulers using the light slit method (through the light), while the pattern ruler is placed with its sharp edge on the surface being checked, and the light source is placed behind the ruler and the part being tested.

Rulers with a wide working surface are divided into four types: rectangular cross-section (Figure 8, G), I-section (Figure 8, d), bridge rulers (Figure 8, e) and triangular (Figure 8, and) with angles of 45, 55 and 60°

Checking straightness and flatness with rulers with a wide working surface is carried out by linear deviations (using a probe) and paint. When checking for paint, the surface of the ruler is covered with a thin layer of soot mixed with machine oil (Figure 8, h, And), placed on the surface to be tested and the accuracy of the plane being tested is judged by the number of spots on a 25x25 mm square.

Quite accurate results are obtained by using strips of thin paper or metal foil, which are placed at certain intervals under the straight edge. By pulling the strips out from under the ruler, the amount of deviation from straightness is judged by the tension force of each of them. By measuring the thickness of the strips with a micrometer, you can determine the clearance value with an accuracy of 0.01 mm.

Verification plates (Figure 8, k, l) are the main means of checking surface flatness using the paint method. The plates are made from high-quality cast iron grade SCh 18-36, fine-grained structure, hardness HB 170-241.

The sizes of the slabs are 250x250, 400x400, 400x630, 630x1000 and 1000x1600 mm. The maximum deviations from the flatness of these plates depend on their size and accuracy class (classes 01; 0; 1 and 2) and are taken from 4 to 25 microns for a plate size of 400x400 mm.

The flatness of the slabs is checked with a straight edge against the light and using a set of plane-parallel end blocks, as shown in Figure 8. n . To do this, two gauge blocks 2 of the same size are placed on the surface of the plate 3 being checked, and a ruler 1 is placed on top of them, and a set of gauge gauges is inserted into the gap between the surface of the plate and the blade of the straight edge. 4. Difference between gauge blocks 2 and the set will show the amount of bending of the surface of the slab being tested.

Verification plates serve not only to control flatness, but they are widely used as a basis for various control operations using universal measuring instruments.

Corner plates (scraper squares), shown in Figure 8, m , They are used to check the mutual perpendicularity of planes using the paint method and are often used as auxiliary devices for various inspection, assembly and marking work.

1.7 Means of control and marking of corners

To check or mark angles, the following types of tools are used: squares, universal and optical protractors, flat corner tiles, sine rulers, optical dividing heads.

Test squares are designed to check and mark right angles, to control the mutually perpendicular arrangement of surfaces of parts during their manufacture and assembly. The industry produces testing squares with angles of 90°. There are pattern squares - for precision work and metalwork squares - for ordinary use.

Pattern squares are made hardened, precisely ground and finished. They are used for transmission testing of precisely manufactured parts. Pattern marking squares have a wide base (shelf) with which the square is pressed against the edge of the part to be marked.

According to the standard, the industry produces pattern squares of two accuracy classes: 0 and 1. For all squares, the height is made longer than the base. The standard provides for the following dimensions of the sides of pattern squares: 60x40, 100x60, 160x100 and 250x160 mm. In Figure 9, a, b curved squares of the ULP and ULSh types are shown. In Figure 9, V

a solid pattern square of the UL type is shown. it is used when checking precision parts of complex shapes on a surface plate and monitoring the assembly of small-sized precision dies, fixtures and molds. In Figure 9, G

a hollow cylinder-square of the ULC type is shown, which is used to check on the surface plate the correctness of the 90° angle for all other squares. Angles of the ULC type are produced in the following sizes (height x diameter in mm): 160x80, 250x100, 400x125 and 160x630.

The measuring surfaces of corner gauges have the ability to rub against each other similarly to plane-parallel end gauges, which makes it possible to assemble blocks of several tiles. Checking corners using corner tiles is carried out against light.

Angle measures are produced in sets in the form of sets of three accuracy classes: 0, 1 and 2 with tolerances of ±3, ± 10 and ±30 s, respectively.

Each set of angle measures comes with a straight edge and a set of holders with holes and clamps for holding multiple tiles assembled into blocks. For this purpose, the corner tiles also have several holes (Figure 9, h, i, j).

Sine bars. Used for precise checking, marking or installation of corner parts of templates and gauges. Conventional sine bar (Figure 9, l) It is a precisely ground steel rectangular plate 7 with two prismatic cutouts in the side faces. Two steel rollers, precisely ground and finished, are attached to the cutouts. 8 certain diameter d(Figure 9, m). The rollers are located at a given distance L. Planks can be attached to the side edges using screws 5 And 6. On the upper plane of the ruler there are smooth threaded holes for fastening with screws additional mounting strips or the workpiece directly (for example, when marking).

To set the ruler at the required angle to the plane of the surface plate 9 under the roller 8 place a block of plane-parallel gauge blocks 10, the size of which H is determined by the formula

,

Where L- the distance between the centers of the rollers.

If the height of a block of tiles is known and it is necessary to find out the resulting angle a, then the calculation is carried out according to the formula

L .

Standard sine bars are produced in the 1st and 2nd accuracy classes and have the following gradation of main sizes:

The distance between the centers of the rollers is 100; 200; 300;

500.

Roller diameter 20; 20; thirty; thirty.

angles up to 45° are measured on sine rulers. Goniometers. To measure the angles of parts, universal protractors with a vernier are widely used. The most widely used goniometers are the UM type (Fig. 30, A)

and UN type (Fig. 30, b).

The UM type goniometer allows you to measure angles in the range from 0 to 180° with an accuracy of 5 minutes. 4 The UN instrumental protractor is more convenient. It is built on the principle of a circular scale and allows you to measure angles ranging from 0 to 320°. On the arc 5, The scale divisions are shown in degrees. A sector moves along an arc, on which a beveled arc bar 3 is mounted, having vernier divisions from 0 to 60. Squares are attached to the protractor 2 and a ruler 6 with a beveled measuring edge, as well as two clamps 1 for attaching the square and ruler to the protractor.

When assembled (with a square and ruler), the protractor makes it possible to measure angles from 0 to 50°. If you remove the ruler 6 and the clamp securing it, the angle measurement limit will change from 140 to 230°. If you install a measuring ruler in place of the square, then angles can be measured in the range from 50 to 140°. Finally, a protractor without a square or ruler allows you to measure angles from 230 to 320°. The vernier reading accuracy on this protractor is 2 minutes.

In Figure 10, V an optical inclinometer of the UO type is shown. Ruler 12, having a slot along the axis, rigidly connected to the body 16, inside which the limb is fixedly fixed 15, having a full angular scale with G divisions. The scale is divided into four quadrants, digitized from 0 to 90° every 2°. Ruler 8 can be moved off-axis and rotated around the center of the body 16 at a certain angle relative to the ruler 12.

In a longitudinal position the ruler 8 secure by turning the stopper 10. In the longitudinal groove of the ruler 8 includes a key connected to the upper disk, on which a magnifying glass 7 is installed with a magnification of x16 and glass 14 with scales having division values 5".

In the field of view of magnifying glass 7 two scales with division values ​​are visible 5" and an image of part of the dial 15, illuminated through glass 14. The angle between the rulers is set by turning the knurled ring clockwise 9 and secure with a stopper 10. Stand 13 with a flat surface and with a prismatic recess, it is used to install the protractor on a flat or cylindrical surface.

1.8 Indicators

Indicators are removable reading devices with a measuring mechanism that convert small measured deviations into large movements of the needle. For the purpose of measurement, indicators are installed on stands, tripods or mounted in special devices that ensure accuracy and convenience when performing work.

In the manufacture of technological equipment, dial indicators with scale divisions are most widely used.

0.01 mm.

These devices (Figure 11) are used for relative or comparative measurements, checking deviations from a given shape, as well as the relative position of the surfaces of parts. They check the horizontal and vertical position of planes and individual elements of parts, ovality, taper of the outer surface of parts and holes, alignment of the hole with the surface of the part, runout of shafts, spindles, flywheels, gears and other rotating parts.

The operation of dial indicators is based on the use of a special gear transmission device, which converts minor linear movements of the measuring rod into enlarged and easy-to-read movements of the arrow on a circular scale.
Dial indicators come in two designs: type I - with the measuring rod moving parallel to the scale and type II - with the measuring rod moving perpendicular to the scale (end-mounted). Type I indicators have measurement limits from 0 to 5 mm and from 0 to 10 mm, type II indicators are manufactured with measurement limits from 0 to 2 mm and from 0 to 3 mm. For particularly precise measurements, use multi-turn indicators with a division value of 0.001 mm and a measurement limit of

0 to 2 mm. The indicators shown in Figure 11 are a, b, 1, consist of a body 2, stopper 3, dial 4, rim 6, reference pointer 5, speed indicator 8, lug 7, sleeves 9 measuring rod 10. and tip 4. Setting the indicator scale to zero is done by rotating the scale by the rim Mounting indicators in racks (Figure 11, V) 8.

produced by eye 7 or by sleeve

1.9 Calibers

Calibers are scaleless measuring instruments.

The gauges can measure one size. Calibers are divided into normal and limit. Normal gauges have a nominal size indicated on the drawing. The accuracy of the measurement depends on the qualifications of the controller. Limit gauges are used to check the size limits. One of the caliber sizes corresponds to the smallest permissible part size, the second to the largest. The first size is called pass-through and is designated by letters ETC, the second is impassable and is designated

NOT

(Figure 12).

Digital measuring instruments, built on the basis of the instruments discussed above, but equipped with microprocessor devices for converting measurement results and displaying the result on a digital display, do not have this drawback.

An example of such a device - a caliper with a digital display - is shown in Figure 13.

The use of caliper measuring surfaces is shown in Figure 14.

The relative method of measurement is a method based on comparison of the measured quantity with a previously known value of the measure.

To do this, using a block of tiles, we dial a denomination equal to the given size (Figure 16). The block size must be selected so that the number of tiles is minimal.

Then we reset the caliper readings to “0” (Figure 17).

Then we take measurements and find the deviation of the actual size from the required one (Figure 18).

2. Work order

1. Complete training on safety precautions and rules for working with measuring instruments.
2. Study the design and purpose of measuring instruments for measuring the geometric parameters of machine parts.
3. Obtain details from the teacher for testing. Draw a sketch of the part.
4. Obtain the necessary measuring instruments.
5. Perform measurements of each size using various instruments using absolute and relative methods.
6. Prepare a report on the work done.
7. Answer security questions.

3. Test questions

1. Purpose of control and measuring instruments. Types of test instruments.
2. What is a measure and how is it used in measurement?
3. Plane-parallel measures of length. Their purpose. Types. Use when measuring.
4. Probes. Purpose. Use in measurements.
5. Measuring rulers. Purpose.
6. Application.
7. Vernier tools. Kinds. Purpose. Measurement accuracy. Method of application for measurements.
8. What is vernier? Purpose.
9. Device. Use to improve the accuracy of measurement results.
10. Micrometers. Purpose. Use in measurements. Measurement accuracy.
11. Means for controlling the straightness of surfaces. Use for control.
12. Means and instruments for measuring angles.
13. Indicator heads. Device and purpose. Measurement technique using indicators.
14. Absolute measurement method.
15. Measuring instruments built on this method.
16. Relative method of measurement.
17. Measuring instruments built on this method.

Passameter. Device. Method of measuring with a passmeter. Setting the passmeter to a given size. Setting up a digital caliper to measure using the relative method. 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

technical measurements

measuring tool

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

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. Metal ruler Calipers

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

This is widespread and actively used in technology (especially in mechanical engineering)

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.

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.

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. Metal ruler 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

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

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

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 D55.

Radius meter

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

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.

To control the manufacture of parts, assembly and repair of mechanisms and machines, various measuring instruments are used - tools and instruments. Measuring instruments include caliper tools, micrometers, gauges, rulers, calibration plates, etc.

The main characteristics of measuring instruments are: scale division and division value, initial and final scale values, scale reading range, measurement limits.

The division of the scale is the distance between its two adjacent strokes.

The scale division value is the value of the measured quantity corresponding to two adjacent scale marks.

The initial and final values ​​of the scale are the smallest and largest values ​​of the measured quantities indicated on the scale of the device or instrument.

The range of scale readings is the range of scale values ​​limited by its initial and final values.

Measurement limits are the largest and smallest values ​​that can be measured by a given instrument or device.

In mechanical engineering, linear dimensions are usually indicated in millimeters without recording the name. If the size is indicated in other derived units, then it is written down with a name, for example: 1 cm, 1 m, etc.

The most common tools for measuring linear quantities in mechanical engineering include measuring metal rulers, caliper tools, micrometric tools, etc.

Measuring metal rulers used for non-critical measurements with low accuracy. They are manufactured with upper measurement limits up to 150; 300; 500; 1000 mm. The division value is usually 1 mm. Measurement error 0.5 mm.

Vernier tools used for more accurate measurements. These include calipers used to measure the outer and inner diameters, lengths, thicknesses of parts, etc. (Figure 1); Vernier depth gauges designed for measuring the depths of blind holes, measuring grooves, grooves, protrusions (Figure 2); gage gauges, used for precise marking and measuring heights from flat surfaces (Figure 3).

All of these vernier tools use verniers, which are used to measure fractional divisions of the main scales.

Figure 1 Caliper ШЦ-I 1 - rod; 2 – sponges for measuring internal dimensions; 3 - movable frame; 4 - clamp; 5 - vernier scale; 6 - depth gauge ruler, 7 – sponges for measuring external dimensions

Among the lifting tools, the most widely used are calipers . They come in three types:

ШЦ-I (measurement limits 0-125 mm and measurement accuracy 0.1 mm);

ШЦ-II (measurement limits 0-200 and 0-320 mm, measurement accuracy 0.05-0.1 mm);

ШЦ-III (measurement limits 0-500; 250-710; 320-1000; 500-1400; 800-2000 mm, measurement accuracy 0.1 mm).

With the jaws closed, the zero line of the vernier coincides with the zero line of the main scale. If you move the jaws of the caliper apart by 0.1 mm, then the first stroke of the vernier coincides with the second stroke of the rod. If you move the jaws apart by 0.2 mm, the second and fourth strokes will coincide, by 0.3 mm, the third and sixth, etc.

Thus, when measuring with a caliper, whole millimeters are counted directly on the rod scale to the zero line of the vernier, and fractional (in this case, tenths) fractions of a millimeter are counted on the vernier scale. In this case, the fractional value (the number of tenths of a millimeter) is determined by multiplying the measurement accuracy (0.1 mm) by the serial number of the vernier stroke (not counting zero), which coincides with the rod stroke. When reading the readings, the caliper is held directly in front of the eyes (Figure 4).

Test instruments and measurement technology

The simplest measuring instruments include a scale ruler, calipers, and bore gauge.

The scale ruler is intended for measuring flat surfaces, as well as for determining dimensions measured with a bore gauge or calipers. Scale rulers are manufactured in different lengths from 100 to 1000 mm. The scale division value is 0.5 or 1 mm; to facilitate counting, every 5 and 10 mm are marked with elongated strokes. The zero division of most rulers is applied at the left end. When measuring, the ruler is applied to the part being measured so that the zero line exactly coincides with the beginning of the line being measured. In Fig. Figure 13 shows how to measure using a scale bar.

Rice. 13. Techniques for measuring with a scale ruler

Calipers are used to measure the external dimensions of parts. The value measured by the calipers is then determined by placing the calipers on the scale ruler. Calipers, like the simplest bore gauge, are rarely used.

A bore gauge is used to measure the internal dimensions of parts. The measured value is also determined using a scale bar.

Vernier calipers belong to multidimensional sliding measuring instruments (Fig. 14, a). It is intended for measuring external and internal dimensions and markings.

Rice. 14. Vernier calipers (a), examples of measuring the size and reading measurements with an accuracy of 0.1 mm (b, c, d)

A caliper consists of a rod with jaws rigidly attached to it, a frame with jaws moving along the rod, a device for micrometric feed, consisting of a slider, a locking screw, a nut and a screw.

The frame is moved as follows. The engine 6 is secured with a locking screw, and the frame locking screw is released. After this, by rotating the nut, the screw and the frame associated with it are slowly moved. The caliper has a vernier.

Calipers are produced with a measurement accuracy of 0.1; 0.05 and 0.02 mm. The last two have a micrometric feed, allowing you to install the caliper with high precision. The leftmost strokes of the vernier and the rod are called zero and when the jaws are closed they coincide. To determine the size to be measured, with the jaws of the caliper apart, count the whole number of millimeters that the left zero vernier stroke has passed along the rod, and then find the vernier stroke that exactly coincides with any division of the rod scale. The ordinal number of this division determines the fractions of a millimeter that should be added to the whole number of millimeters. When measuring internal dimensions, the thickness of the jaws, which is indicated on them, should be added to the reading made on the main scale and vernier. Examples of readings are shown in Fig. 14, b, c, d.

A depth gauge (Fig. 15, a) is used to measure the depth of holes, grooves on shafts, etc. Measurement with a depth gauge is carried out in the same way as with a caliper.

A vernier gauge (Fig. 15, b) is used to measure the thickness of wheel teeth. A vernier gauge is a combined measuring instrument consisting of two fixed rods that form a single unit and two movable verniers. The vertical vernier is designed to set the height at which the tooth thickness should be measured, and the horizontal vernier is designed to measure the tooth thickness at a given height. The measurement accuracy of the caliper is 0.02 mm.

The micrometer is used to measure the external dimensions of parts with an accuracy of 0.01 mm. The most common are micrometers with the following measurement limits: from 0 to 25 mm, from 25 to 50 mm, from 50 to 75 mm and from 75 to 100 mm.

The micrometer (Fig. 16) has a bracket into which a hardened and ground heel is pressed, a micrometer screw, a stopper, a stem, a drum and a ratchet.

Rice. 15. Vernier depth gauge (a), caliper gauge (b):
1 - locking screw, 2 - slider, 3 - micrometer screw, 4 - nut

Rice. 16. Micrometer

The ratchet is connected to the drum by a ratchet, pressed by a spring, and 50 divisions are marked on the left end of the drum, beveled along the circumference. The micrometer screw has a thread with a pitch of 0.5 mm, therefore, for one revolution of the screw, its end moves by 0.5 mm, and when the drum is turned by one division, the screw moves by 0.01 mm. On the surface of the stem there are divisions with an axial stroke.

Rice. 17. Micrometric bore gauge (a), extension to it (b)

To measure a part, it is placed between the micrometer screw and the heel, after which the drum is turned using a ratchet and the screw is pulled out until it comes into contact with the part. When the screw rests on the part being measured, the ratchet will turn freely, and the screw and drum will stop. To determine the measured size, you need to count the number of millimeters on the stem scale, including the half-millimeter division passed by the reference stroke (0.5), and then look at what number on the beveled part of the drum coincides with the axial stroke of the stem. This number will correspond to hundredths of a millimeter, which must be added to the previous data.

Rice. 18. Micrometric depth gauge

Rice. 19. Squares

A micrometric bore gauge (Fig. 17) is used to determine the internal dimensions of parts with an accuracy of 0.01 mm. A micrometric bore gauge consists of a micrometric screw (Fig. 17, a), a drum, a sleeve with a locking screw, and a tip with a spherical measuring surface. There is also a spherical measuring surface on the right side of the micrometer screw. Dimensions are measured in the same way as when measuring with a micrometer.

The micrometer bore gauge has a set of extensions that extend the measurement range. At one end of the extension there is an internal thread (Fig. 17, b), and at the other end there is an external thread. The end of the extension with internal threads is screwed onto the stem of the bore gauge, and the end of the extension with external threads is used to screw an additional extension onto it in order to increase the measurement limits.

Rice. 20. Universal protractor of the Semenov system

Rice. 21. Goniometer UG-2

The micrometric depth gauge (Fig. 18) is used to measure blind holes and recesses with an accuracy of 0.01 mm. It consists of a base, a drum, a ratchet, a vernier, a stopper, and a measuring rod. The principle of measuring with a depth gauge and a micrometer is the same.

To measure angles, as well as determine the accuracy of filing planes along the “clearance”, squares and universal protractors are used. Squares (Fig. 19) are usually made of steel.

The UG-1 goniometer (Fig. 20) of the Semenov system is universal, designed for measuring external angles. It consists of a base on which there is a scale from 0 to 120°, rigidly connected to a ruler, a movable ruler, a clamp, a removable square, a vernier and a micrometric feed device.

The UG-2 protractor (Fig. 21) consists of a base, a base ruler, a sector, a square, a removable ruler, clamps and a vernier. This protractor can measure external and internal angles.

On the main scale of protractors, degrees are counted, and on the vernier scale, minutes.

Limit gauges for measuring holes are made in the form of double-sided cylinders (Fig. 22) and are called plug gauges, and for measuring shafts - in the form of one-sided and double-sided staples, called gauge gauges (Fig. 23, a, b). Limit gauges can determine the largest and smallest permissible dimensions of parts.

In extreme gauges, one side is called passable and the other is called nonpassable. The go-through side of the plug gauge is used to measure the smallest hole, and the no-go side is used to measure the largest. With a clamp gauge, on the contrary, the largest shaft size is determined by the go-through side, and the smallest by the non-go-through side. When measuring, the pass side of the gauge must pass freely into the hole or along the shaft under the influence of the weight of the gauge. The non-go side of the gauge should not go into the hole or along the shaft at all. If the non-passing side of the gauge passes, the part is rejected.

Radius templates are used to measure the radii of curvatures of products.

Such templates are made in the form of thin steel plates with convex or concave curves. The templates are stamped with numbers showing the size of the radius of curvature in millimeters.

Probes. To measure the size of the gaps between parts, feelers are used (Fig. 24), which are steel plates of various thicknesses. Each plate indicates its thickness in millimeters.

Thread control is carried out using thread plug gauges, threaded rings and templates.

Thread plug gauges (Fig. 25, a) are used to check the threads of nuts. They are made from tool steel and look like a bolt with a precise thread profile. Checking the thread of the nut is done by screwing it onto the go-through or non-go-through side of the plug gauge.

Threaded rings (Fig. 25, b) are used to check the threads of bolts and represent a nut with an exact thread profile. The bolt thread is checked by screwing it into the threaded ring. One ring is a pass-through gauge and the other is a non-go-through gauge.

The thread gauge (Fig. 26) is designed to check and determine the thread pitch on bolts, nuts and other parts. It is a set of steel plates - threaded templates with tooth profiles corresponding to the profiles of standard metric or inch threads. Thread gauges usually have a set of templates with metric threads on one end and inch threads on the other. Each template is marked with thread dimensions.

Rice. 22. Size control with a double-sided plug gauge

Rice. 23. Double-sided (a) and single-sided (b) staple gauges

Rice. 25. Threaded plugs (a) threaded ring (b)

To check the threads on a bolt or nut, you need to apply the thread gauge templates successively until you find a template whose teeth exactly match the threads of the part without clearance. The measured thread will correspond to the size of this template.

The indicator is designed to measure deviations of dimensions from the specified ones, as well as to detect the ovality and taper of shafts and holes. In the repair business, the dial indicator is most widely used, the structure of which is shown in Fig. 27.

The indicator body contains a mechanism consisting of gears, a rack, a spiral spring, a sleeve, a measuring rod with a tip, a speed indicator, and a scale with an arrow. The large scale of the indicator has 100 divisions, each of which corresponds to 0.01 mm. When the measuring rod moves by 0.01 mm, the arrow will move around the circle by one division of the large scale, and when the rod moves by 1 mm, the arrow will make one revolution. The indicator scale is set to the zero position by rotating it by the rim.

Before measuring the product, the indicator is fixed in the bracket of the universal stand (Fig. 28) so that the tip of the measuring rod touches the surface of the product being measured. Next, behind the rim 5, set the zero division of the scale against the arrow (Fig. 27). After this, the product or indicator is slowly moved. The amount of deviation is determined by the arrow readings on the indicator scale.

Rice. 24. Probes

Rice. 26. Thread gauge

Rice. 27. Dial indicator:
1 - measuring rod, 2 - sleeve, 3, 10, 11, 13 - gears, 4 - scale, 5 - rim, 6 - body, 7 - arrow, 8 - speed indicator, 9 - spiral spring, 12 - spring, 14 - measuring tip

Rice. 28. Indicator with universal stand:
1 - the indicator itself, 2 - articulated lever, 3 - stand, 4 - base

Rice. 29 Indicator bore gauge

An indicator bore gauge (Fig. 29) is used to measure the diameters of engine cylinders. A full turn of the indicator needle corresponds to a change in dimension A by 1 mm. Since the scale has 100 divisions, the scale division value is 0.01 mm. The indicator arrow is set to zero by turning the rim. The indicator comes with a set of interchangeable tips that allow you to measure cylinders of various diameters.

Optical measuring instruments. Measuring instruments based on optical measurement principles include optimeters, instrumental microscopes, and various measuring machines.

Pneumatic instruments are used to measure the external and internal surfaces of precision parts, as well as to determine the cleanliness of surface treatment. Pneumatic devices operate on compressed air, which is supplied by a compressor. The advantage of such devices is the simplicity of their design and maintenance.

Electrical measuring instruments make it possible to make measurements with high accuracy. Such devices are based on electrical contact, capacitive and inductive measurement methods.

Measurement errors and their causes. When measuring parts, there is always some difference between the actual size of the part and the size obtained as a result of measurement. The difference between the measured value and the actual value is called error or measurement error.

The main causes of measurement errors are the following:
– inaccurate installation of the measured part or measuring tool;
– errors when taking instrument readings, which occur in cases where observation when taking readings is carried out from the wrong angle of view. It is always necessary to observe in a direction perpendicular to the plane of the scale;
– violation of the temperature conditions under which measurements must be made. The state standard for measurement provides a normal temperature of 20 °C. In practice, the part being measured often has a lower temperature than the temperature of the measuring tool; this also leads to errors, since it is known that metals change their dimensions when the temperature changes. When cooled they contract and when heated they expand. When heated by 1 °C over a length of 1 m, metals elongate by the following values ​​(mm): steel - 0.012, cast iron - 0.010, bronze - 0.018, brass - 0.019, aluminum - 0.024;
– the surface of the part being measured is dirty or dirty;
- measuring tool;
– errors of the measuring instrument;
violation of the constancy of the measuring force for which the measuring instrument is designed.

Storage and care of measuring instruments. Measuring instruments are stored in dry, warm rooms. Do not store instruments in damp rooms or in rooms with sudden temperature fluctuations, as this will lead to corrosion of the instruments. Each tool should have its place.

The simplest tools are stored in cabinets, on racks or hung on the walls. Complex instruments, such as micrometers, calipers, gauges, etc., are stored in special cases.

To protect against corrosion, measuring instruments are lubricated with acid-free Vaseline or bone oil. For long-term storage, the instrument is wrapped in oiled paper to protect it from contamination and exposure to humid air. Before work, the measuring surfaces of the instrument are washed with gasoline and wiped with a clean cloth, and after finishing work they are wiped again, then lubricated and put in their place.

Measuring instruments must be checked regularly using precision test instruments.

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