Measuring instruments and tools types. Testing and measuring instruments. Analog and digital

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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. Rotational movement, for example, a screw is connected 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.

Optimeter - measuring device with a division value of 0.001 mm - 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.

Devices designed to determine the geometric parameters of parts are called measuring instruments. Such devices include:

calipers;
depth gauges;
plumbs, levels;
rulers, etc.

Classification of measuring instruments

When carrying out work related to the manufacture of various parts, repair and construction work, etc., control and measuring tools are used. Enterprises engaged in the production of these products produce many types of measuring instruments - manual, universal, digital, etc.

Hand-held measuring instruments include rulers, tape measures, squares, calipers, micrometers, etc. Most of hand tool refers to a universal measuring tool. Such products can be used when taking measurements of most parts and assemblies.

To perform accurate measurements, use a tool with a laser installed on it. Such products are used in construction - these are levels, rangefinders, and other products intended for marking the front of work or conducting geodetic research. The laser measuring tool is easy to use and the readings taken are accurate. Most of these tools can transfer the received data to a computer for further processing.

The construction measuring tool has found its application on the construction site. It is easy to operate, manual, and not highly accurate. At the same time, tools are used on the construction site that use laser ray. This allows you to take measurements with an accuracy of a fraction of a millimeter.

The caliper tool consists of two control surfaces, between which the size is set. One surface is part of the rod, on the second there is a movable or fixed control ruler, on which dimensional marks are applied. They may have different division values depending on the accuracy of the instrument.
A tool of this class is used to measure external and internal dimensions - calipers, to measure the depth of the groove. This type of tool is used to control the tooth dimensions in a gear.

Measuring heads are devices that convert the movement of the measuring tip into the movement of a pointer on a circular marked scale. These devices are used, for example, to measure the runout of a part clamped into a chuck lathe. To make it easier to work with such a head, in factory slang it is called a “watch”; stands or tripods are used. Measuring heads are divided into:

spring;
lever-geared;
lever

The main element of a micrometer instrument is the spindle, on the surface of which a particularly precise thread is applied. This instrument is capable of taking measurements with an accuracy of 0.01 mm. Micrometric instruments are installed in brackets, devices, etc. Representatives of this class of instruments are micrometers, micrometric internal and depth gauges, etc.

Device and technical characteristics

Most of the measuring instruments are standardized by GOST requirements. In the system of standards adopted in our country, there are at least a hundred of them. Based on GOST, manufacturing enterprises have the right to issue their own technical specifications (TU) for the production of certain products. It must be understood that a tool produced on the basis of specifications is in no way inferior to one that meets the requirements of GOST. But historically, if, for example, GOST 20162-90 is indicated on the passport that is supposed to accompany any instrumental product, then such products inspire greater confidence on the part of consumers.

Meanwhile, the design of measuring instruments and instruments is no different from those produced on the basis of specifications. This does not apply to those instrumental products that are made in a handicraft manner, and their testimony cannot be trusted by definition.

Requirements for measuring instruments and tools, as noted above, are defined in GOST. As an example of the requirements for a measuring instrument, we can consider a measuring ruler, GOST 427.

It defines what types and shapes of metal rulers are produced. It is determined what types of scales can be applied to the surface of the tool. The same document regulates tolerances for dimensions, the maximum deviations that relate to the marking of the metal ruler are indicated.
The material from which this class of tool can be made is determined, and the coatings that are applied to the surface of the product are described.

GOST takes the procedure for accepting finished products very seriously. In addition, the procedure for storing, packaging and transporting cargo is no less carefully determined.

Using the measuring tool

Our country has a State System for Ensuring the Uniformity of Measurements (GSI). Among the many problems that it is designed to solve, the following can be highlighted:

State metrological control, which includes verification of measuring instruments; approval of types of measuring instruments; issuance of licenses for the production and repair of measuring instruments.
Metrological control over production, the use of measuring instruments, standards of measurement quantities, measurement techniques and other issues related to measuring instruments and methods.

Structurally, the GSI is part of the Rosstandart FA and, accordingly, all questions regarding the verification and certification of measuring instruments must be addressed to the regional branches of the federal agency.
To ensure the quality of products manufactured, constant control over dimensions, tolerances, and fits is necessary. To carry out this work, the company must use only high-quality tools. Almost all measuring instruments must undergo a verification procedure. Verification (not to be confused with verification) of a measuring instrument is a set of certain activities carried out to confirm the compliance of measuring instruments with metrology requirements. Instrument verification must be carried out in specially certified laboratories.

Caliper verification procedure

GOST 8.113-85 defines the methodology for checking calipers. It includes the following operations:

Inspection of appearance.
Testing.
Determination of metrological parameters.
Determining the size of the sponge outputs.

A total of 14 types of inspection and diagnosis of the caliper condition are provided. To carry out verification, certain instruments and technological devices must be used in the laboratory. For example, to determine the surface roughness of the jaws, a profilograph according to GOST 19299-73 or a profilometer according to GOST 19300-73 is used; in addition to these devices, roughness samples must be used.

A tool that has been verified accordingly is marked and can be used in production. Those devices that do not meet metrology requirements must be immediately written off. In accordance with the requirements of the QMS (quality management system), there should be no untested tools in the workplace.

By the way, when launching new products and its equipment into production, it is necessary to take into account the fact that not every instrument, no matter a tape measure, ruler or others, is accepted by laboratories for verification. There are enterprises whose products and metrological laboratories do not accept verification. This does not apply to serial tool factories, for example, Kirov or Chelyabinsk. Therefore, before purchasing a measuring instrument, it makes sense to clarify the instrument from which company you can purchase without fear.

Specifications for repair of measuring instruments

Careless storage and use sooner or later leads to measuring instruments failing or even breaking down. But, it should be noted that even with full compliance with the operating rules, the tool will still wear out.

To determine the suitability of a tool for use, appropriate tests are carried out, as a result of which it becomes clear whether it can be used or not. If, after repair and repeated testing, the instrument does not meet the accuracy requirements specified in the regulatory documentation and passport, then it is permissible to transfer it to a lower class. But at the same time it is necessary to make changes to the passport or form.

To identify major problems, it is necessary to use high-precision tools. These include gauge blocks, rulers, and high-precision caliper tools. To carry out tool repairs, it is necessary to attract highly qualified specialists, for example, a sixth-class toolmaker who knows all methods of metalworking material processing, including the use of mechanization. At large enterprises, there are separate tool production facilities that are involved in the repair and restoration of measuring devices.

Control, measuring and marking

Among vernier calipers, the most common failures are the wear of the dimensional surfaces of the jaws or their sharp ends. In addition, over time, abrasion occurs on the surfaces of the rod and the frame moving along it. Often, the vernier in the frame is displaced, and the screw pair wears out in the micrometer instrument.

Defect detection

To identify the skew of the jaws, it is performed by measuring the end gauge in different spatial planes. If different measurement results are detected, the parallelism of the working surfaces can be judged. When they become excessively worn, a discrepancy between the main and vernier scales appears.

To obtain data on rod defects, a straight edge or plates with paint are used.

To eliminate non-parallelism of the working surfaces, the following operations must be performed. The tool is healed in a yew and, using a lapping device, the detected defect is eliminated. When performing this operation, do not apply much force. After the jaws are ground in, set the vernier to a new position.

If a curvature of the tool rod is detected, it must be straightened. To do this, it is fixed in metalwork yews. Then, using a lapping plate, it must be brought to an even state. To remove small potholes, use a velvet file.

In more complex cases of caliper failures, they also use heat treatment, and machine equipment. All these are quite labor-intensive processes and can only be performed by high-level professionals.

Therefore, before making a decision to replace or repair a measuring instrument, it is necessary to calculate the economic feasibility.

Features of micrometer instrument repair

A micrometer instrument may be sent for repair in the following cases:
When wear is detected on the measuring surfaces. If wear is detected on micrometers with a small measuring range, it is eliminated using measuring laps. If the separate grinding method is chosen, then repair equipment of different designs is used for this. During operation, it maintains a strict vertical position of the workpiece relative to the lap plane.

This device includes a plate, a collet and a clamping ring. The bottom plate is oriented perpendicular to the axis of the hole. The screw is installed in the collet and fixed so that its tip protrudes above the surface of the plate to a height of 0.03 - 0.04 mm. The device used to restore the heel has a similar design.

If the zero mark on the drum does not coincide with the corresponding scale division on the rod. The head of the device must be unscrewed 1 - 2 turns. After this, you need to remove the drum by pulling it towards the bracket. After this, it must be installed in the required position. The head must be returned to its original position and then fixed with a screw.

Undoubtedly, measuring devices after repair and restoration work most often do not meet the requirements of the standards. For such cases, technical conditions are provided that indicate permissible deviations from the standard.

In particular, the presence of simple damage - scratches, gouges - is acceptable. But, most importantly, they should not interfere with measurements and should not exceed more than 20% of the total surface of the instrument.

If during repair and restoration work on the instrument the surface was straightened, then its traces must be eliminated. To do this, grinding or decorative coating is applied.
For a vernier tool there are also additional conditions, for example, for a caliper with a division value from 0.02 to 0.05 mm, the distance between the supporting rod and the vernier should not exceed 0.05 mm. The length of the measuring surface on the jaws should not be less than 7 mm. The diameter of the circle describing the blunt jaws should not be less than 7 mm.

The plumb line is probably the simplest tool known since ancient times. And just like five thousand years ago, it was used to check the verticality of walls, partitions and other parts of building structures and metal structures.

The design of this tool is extremely simple; it consists of a cord and a weight attached to its end. The plumb line is always directed strictly perpendicular to the surface, and it is this property that allows it to be used to check the verticality of structures. You can buy a plumb line, or you can make it yourself; for this you need to pick up, for example, a nut and tie it to a cord. Commercially produced plumb lines are coated to protect them from corrosion.

Probes

To measure the gap between parts, for example, in a sliding bearing, a tool such as a feeler gauge is used. The probe is a set of plates made of durable steel. One set includes strips of different thicknesses. The surface is usually marked with a marking indicating its thickness. To take measurements, you can use one strip, or several.

Styli are used in various industries - mechanical engineering, construction, repair of propulsion systems, etc. Styli are used for adjusting valves, bearings, when aligning shafts, etc.

Domestic and foreign manufacturers produce probes in four sets, each of which can contain from 9 to 17 plates. The length of one plate is from 75 to 100 mm. The thickness of the plates ranges from 0.02 to 1 mm. In their activities they must be guided by GOST 882-75 or technical specifications made on its basis.

This tool has been around for thousands of years and is used for marking and checking the perpendicularity of sides in mechanical engineering and construction.
In accordance with GOST 3749-77, manufacturing enterprises produce several types of similar products - UL - patterned; ULP - flat patterns; ULC - patterned cylindrical; UP - metalworker's flat; USh - metalwork with a wide base. GOST defines their geometric dimensions, maximum deviations and other information necessary for their production.

In addition to these measuring instruments, angles used in construction are produced. But it should immediately be noted that non-ferrous metals are used for their production, in particular, the support can be made of silumin. The use of measuring instruments of this type in mechanical engineering is undesirable.

Why do precision measuring instruments indicate temperature?

The answer to this question lies on the surface. The metal parts of measuring instruments are temperature dependent. That is, when the temperature fluctuates, errors in the measurement results may occur. The temperature shown on the instrument, usually 20 degrees, indicates that the most accurate readings will be obtained at this temperature.

Control, measuring and marking tools

To obtain high-quality products and perform work in everyday life, various measuring instruments and devices are used. They are used to obtain accurate linear and angular dimensions, voltage readings, current readings, etc.
To make life easier for consumers, all means of measurement and instrumental control can be divided into basic groups:

tool;
measures;
devices.

The first category includes simple instruments for taking measurements - rulers, caliper tools, etc. These devices are used when taking measurements in a wide variety of industries, from space to apartment renovation.

Measures include products that can store and reproduce physical quantities and their properties, for example, gauge blocks, gauges, etc.
Measuring instruments have a more complex configuration and assume that a measuring instrument can be used. This group includes bore gauges, etc.

Measurement and control

Measurement is the procedure for determining size using technical measuring instruments. That is, a comparison of physical characteristics with a certain conventional unit.
Units of measurement include millimeter, foot, and others. In practice, the concept of measurement is understood to identify the dimensions of parts and workpieces, their deviations, the size of roughness and surface cleanliness, and many others. The instrument used to carry out such measurements is called a scale instrument. Since it has measuring scales installed on it.

Control is the identification of the part’s compliance with the required standards, working documentation, etc. Tools of this class are classified as scale-free. With its help, you cannot find out the absolute size, but you can clarify the correspondence of the shape of the part. Such a tool is used both in the production process and during product inspection and acceptance.

Control and measuring equipment can be classified as follows:

one- and multidimensional;
manual, mechanized, automated.

Measuring devices and instruments can be divided into the following groups:

mechanical and micrometric;
lever-mechanical;
toothed;
optical, etc.

In the instrument market, measuring devices using lasers are in great and steady demand: rangefinders, levels, protractors, etc.

A measuring instrument in the form of a parallelogram, which can be made of polymer or metal and with flasks filled with water installed in it, is called a level or spirit level. Its main purpose is to assess the conformity of working surfaces to the vertical or horizontal. There are several versions of this device.

The most modern ones include laser. Most often it is used when performing construction work on objects for various purposes. In addition, they are used when performing finishing work. Using this tool you can do the following:

control of markings intended for installation of industrial and household equipment;
laying utilities;
leveling wall and floor coverings.

Another type of level is hydraulic. It is a transparent tube filled with water.

A universal measuring tool designed to measure dimensions - external and internal - is called a caliper. Some models are equipped with a depth gauge built into the support rod. This measuring device is perhaps the most common. It can be found in the workshop of a machine-building enterprise and in a garage workshop.

A caliper is a ruler with two jaws. One is integral part, bearing ruler, the second sponge moves along it. To measure thickness or outer diameter, jaws are used with the cutters facing inward. To measure internal dimensions, for example, the width of a keyway, jaws are used that face the cutters upward.

To measure large linear dimensions, use a tape measure. It is a tape on which divisions are applied. Depending on the type, it can be used to measure distances from one to fifty meters.

The tape can be made of steel strip or polymer tape. It is wound onto the housing and placed in a housing in which a return spring is installed; it allows the tape to be wound after taking the measurement. It is used for marking workpieces, land plot and many other types of work. For more accurate measurements, use a laser tape measure.

So, they call a measuring instrument assembled into a single structure from metal, wooden or plastic pieces. When unfolded, it reaches a length of one meter. The length of one link is usually 10 cm.

This type of tool is also used in industrial production and construction. Most often, a folding meter can be seen in a carpentry workshop.

In any production that involves making something, it is impossible to do without measurements. Regardless of whether GOST requires this or you are creating a new product, you still have to measure it. We will now talk about how and with what to measure correctly. Discarding specialized geodetic instruments, without returning to ancient times to a rope with knots and a stick with notches, and without looking into the future with laser rangefinders, we will discuss simple, convenient, and most commonly used measuring tools.

Purpose and types

Speaking about their purpose, measuring instruments are classified according to their area of application into:

construction;
carpentry;
locksmiths.

A separate group can be identified as a universal measuring instrument that can be used in all or several industries.

By type, instruments are divided as follows:

This division into classes and types of measuring instruments is necessary for their professional use in work, compliance with storage and operation rules, purchase in stores and delivery from warehouses in factories.

Construction measuring tools

Roulette. Used to measure linear dimensions of length, width, height. It is a housing made of solid material (plastic, metal), inside of which there is a metal or polymer tape. Available in different widths and lengths, but with the same scale, the graduations of which are 1 mm. Roulettes come with a manual or mechanical (spring) winding principle.
Water level. Used for horizontal marking in height. Consists of a flexible polymer tube (length from 5 to 30 m) and two volumetric flasks at the ends. It works on the principle of communicating vessels.
Level (spirit level). It is necessary to determine both horizontal and vertical indicators of structures. Made from various materials(wood, plastic, aluminum). The length ranges from 30 cm to 2.5 m. It mainly has three windows with glass tubes. The tubes are not completely filled with antifreeze liquid. The operating principle is vertical air lifting.
Plumb. Used to set vertical values during installation and construction. It has simple design from a cord on which a cone weight is suspended. Sometimes, in strong winds, to compensate for lateral vibrations, the load is placed in a container of water.
Square. Made from wood or metal. It has a length of each side of up to 1 m. It is indispensable in the construction of buildings for checking right angles.
Malka. Like a square, it can be metal or wood. The difference is that the two wings (clip and ruler) are hinged. Mainly used in the construction of roofs to install rafter pairs. Having set the desired angle, fix it with a wing nut and check the design.

Carpentry measuring tools

Considering the contiguity of some professions and the versatility of the measuring instrument, we will single out only the meter and the triangle separately. A tape measure is generally a universal tool, and we have already talked about a square and a small tool. They with shorter side lengths (up to 50 cm) are widely used by carpenters. A caliper is also used, for example, to select drills or check the diameter of holes, but we will talk about it later.

Meter. The main material is wood and stainless steel. A plastic version was also produced, but due to its fragility it was not widely used. The name speaks for itself - meter, division value is 1 mm. Its main difference from a meter ruler is that it consists of separate sections that fold and unfold if necessary.
Triangle. Everyone from school remembers this instrument and the size of its angles - 90, 60, 45 degrees. This is why it is widely used by all woodworkers. Usually the square also has a bevel of 45 degrees, but, firstly, not everyone does, and secondly, the dimensions do not always allow them to be used. This is where the triangle comes in handy. The main material is plastic, as well as wood or metal.

Locksmith measuring tools

Taking into account the specifics, scope of application, as well as the conditions when dimensions range from 0.1 mm to 0.005 mm, we can say that a locksmith is the most accurate measuring tool. And it's not just about accuracy. The work itself requires attentiveness, and the plumbing measuring tool requires knowledge and experience. Often the same device is used to measure different parameters.

Let's look at the indispensable assistant - calipers. Its upper lips are used to take internal dimensions of parts, and its lower lips are used to measure external parameters. In addition, the caliper has a depth gauge on a movable frame. But that's not all. On the main rod there is a scale for counting whole millimeters (division value - 0.5 mm), and in the cutout of the frame there is a Vernius scale for reading fractions of millimeters (division value 0.02 mm.). There is also a locking screw that secures the frame to the rod.

Yardstick It is a polished steel strip 20-30 cm long with marked divisions of 1 mm. It is used for linear measurements that do not require high accuracy.

For more accurate measurements, as well as angle measurements, measuring tools such as micrometer and protractor. They also have two scales - main and vernier. Often used calipers and bore gauge for measuring the external and internal dimensions of parts, respectively.

The specialist also has a variety of control and measuring instruments in his arsenal:

straight edges of different configurations (double-sided, three-sided and tetrahedral);
corner and reference tiles;
measuring indicator;
various probes.

Storage conditions

If we take into account the materials from which measuring instruments are made, it becomes clear that they cannot be stored under the same conditions. If plastic and plastic instruments are less susceptible to moisture, then wooden and especially metal instruments are afraid of water ingress. In this regard, they need to be stored in a dry, ventilated area. In addition, wooden tools must be protected from direct impacts. sun rays to prevent it from drying out. Precision instruments are best stored in protective leather cases, and some instruments are best stored in hard wooden or plastic boxes.

Using the measuring tool

First of all, the measuring instrument you are working with must be in good working order, clean, and without traces of rust or oxidation. No mechanical impact is allowed (impacts, pressure, bending). Try to avoid dropping the instrument or getting water on it. Before operation, read the instructions, if any. Skillful and correct handling of the measuring tool is the key to quality work.

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

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. 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.

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 activity 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 instruments 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 plumbing 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.

Of great importance for accuracy are physical properties processed materials, their ability to change parameters depending on climatic conditions. 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. Forward movement the screw is communicated with the help of 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 with the screw and the heel on both sides;
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 stem below: 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. Mark on the drum scale exact value hundredths of a millimeter. Final part size equal to the sum data from all scales.