In some cases, when measuring objects, high precision results are required, which cannot be obtained using a conventional ruler. In such situations, special micrometric instruments are used. What a micrometer is and how it is used is described in this article.

What is a micrometer device

This is a tool designed to accurately measure small parts. The micrometer allows you to determine the thickness, depth, outer and inner diameters of products. To perform these measurements, micrometer depth gauges, bore gauges, and other micrometers of various designs are used.

All variations of this work on the same principle: using the mutual movement of a nut and screw. Among all micrometer mechanisms, conventional micrometers are the most common.

A micrometer is a small metal instrument that consists of a screw, a clamp and a tip. It allows you to measure objects with a high degree of accuracy. The instrument error is very small and ranges from 2 to 9 microns. It should be noted that 0.1 mm = 100 microns, that is, 1 micron is a millionth of a millimeter. The maximum screw movement is 25 mm. This length contributes to the maximum. If the length of the micrometer screw were longer, the measurement results would not correspond to reality. Some models of micrometers allow you to measure products up to 100 mm in size through the use of replaceable anvils.

There are strict technical requirements that a micrometer must meet. GOST specifies that all models must have an accuracy of 0.01 mm. Also, according to standards, micrometers can be produced with the following measurement limits: 0-25, 25-50, 50-75, 75-100 and so on up to 300 mm, and then 300-400, 400-500, 500-600 mm.

History of origin

Humanity has known for many centuries what a micrometer is. According to historical facts, the screw measuring mechanism began to be used back in the 16th century in the sighting mechanisms of artillery weapons. A little later, the tool began to be used in geodetic devices. But it did not give the required accuracy of results. It was only in 1867 that American engineers created a micrometer that made it possible to obtain high-quality measurements.

Types of micrometers

The micrometer is the most versatile measuring mechanism. Ease and ease of use have made it almost indispensable in many industrial areas. Due to the variety of measuring objects, the following types of micrometers are produced:

• sheet - designed to measure the thickness of flat sheets made of metal or other material;
• lever - differ from other micrometers by the presence of a lever-toothed head, which makes it possible to produce complex products or repair them with high precision;
• smooth - devices of this type are equipped with a bracket and ratchet, which allow you to measure objects with a smooth surface; smooth micrometers are the most common and are used in almost all industrial sectors;
• universal - designed for taking internal and external dimensions of various parts;
• pipe - used for measuring pipe walls;
• thread and wire gauges - make it possible to measure the thinnest products, for example;
• digital - measurement with a micrometer of this type provides additional advantages: data recording and the possibility of instant processing on a computer.

As for production, two types of micrometers are most widely used here - mechanical and digital. Let's look at them in more detail.

Mechanical micrometers

A mechanical micrometer is a traditional measuring instrument and is widely used in various sectors of the national economy, despite the presence of a more advanced electronic analogue.

The mechanical micrometer device consists of two parts:

• handles (ratchet, stem and drum);
• a semicircular recess with a support stand for fixing the object being measured.

To measure a part, you need to follow this scheme: first you need to place the object on the support stand and tighten the micrometer screw with a handle. After this, you need to turn the ratchet to adjust the measurement. When it starts to scroll, it means the measurement has already been made. The last step is to read the values ​​from the scale located on the drum and stem.

There are models of micrometers that are equipped with a locking mechanism. It allows you to hold the ratchet in place so that the recorded value does not go astray while the result is recorded in a special book or journal.

Digital micrometer

The electronic instrument is an improved form of the simple mechanical micrometer. It is more modern and convenient to use. Thus, a digital micrometer allows you to obtain measurements with an accuracy of up to 1 micron and an error of up to 0.1 microns. Many models have built-in calibration.

Externally, the electronic device differs from the mechanical model in the presence of a digital display. The user can choose any of the possible calculation systems. For example, inches or millimeters. The board also displays other important information. So, you can view the battery charge level at any time.

To reduce energy costs, the device can be programmed to turn off automatically. This mostly happens after 5 minutes of inactivity.

There are technical requirements that a digital micrometer must meet. GOST designates the division scale, permissible errors and other important features of the device.

How to use the device

1. Checking the tool. Immediately after purchase, you should check the device for suitability and absence of defects. If the micrometer is working properly, then you need to adjust the scale. For this purpose, a special key comes with the tool. If everything is done correctly, the display of the digital instrument should show 0 when the measuring planes are closed without the part. In a mechanical micrometer, the drum should cover the stem, and the zero value of the drum scale should coincide with the longitudinal line on the stem. It is advisable to do such manipulations periodically in order to be able to identify faults in time and adjust the micrometer. This will prevent incorrect measurements in the future.
2. Fixing the part. This stage is very important and requires compliance with important recommendations. So, first you should place the object between the measuring planes and simple rotations of the drum bring the screw to the part. After a short rotation, you should feel a stop. Then you should move along the handle and continue to turn the ratchet until three clicks sound. This will be a signal that the part is securely fixed.
3. Measurement with a micrometer. After fixing, the digital device will show the measurement result on the display. As for the mechanical device, this will require a little tinkering. The result must be read from large numbers and ending with small ones. First you need to look at the marks on the stem. There are two scales on it. The upper divisions indicate 0.5 mm, and the lower divisions - 1 mm.

Industrial Applications

Micrometric instruments are indispensable in modern industry. This is especially true for industries that work with small parts. Thus, almost all instrument-making enterprises use a micrometer. This allows parts to be produced with a high degree of precision. The measuring device is also used in the jewelry industry to measure the size of stones.

It is impossible to do without a micrometer at many stages of automotive manufacturing. That is, micrometric tools are used wherever production involves small and medium-sized parts.

Micrometer cost

There are a wide variety of micrometers on the market today. The large selection of tools is explained by the active growing demand for micrometers. The price of different device models may vary significantly. It depends on functionality, material strength, reliability. The manufacturer has a big influence on the cost of the tool. As a rule, a micrometer costs much more than a regular Chinese one. In this case, the buyer himself decides what is more important - saving on the device or having a high-quality measuring mechanism. Thus, the price of a digital smooth micrometer is in the range of 90-200 euros. And a regular mechanical device can be bought for only 19 euros. More complex models with built-in digital displays, levers, and replaceable measuring elements are much more expensive.

1. Before using the micrometer, you should keep it and the measuring object at the same temperature for 3 hours.
2. The markings on the scale may differ in different micrometers. Therefore, before calculating measurements, you should read the instructions and carefully understand the values ​​of the marked divisions.

Now you know what a micrometer is and can use it in practice.

Micrometric instruments. .

Micrometric instruments are used to accurately measure outer and inner diameters, thicknesses and depths. These include: micrometers of various designs and purposes, micrometric bore gauges and micrometric depth gauges. All types of micrometer instruments work on the principle of using the mutual movement of a screw and nut. Micrometers are the most common. They are produced in the following types: ordinary smooth micrometers, micrometers with flat inserts, lever micrometers, threaded micrometers. All micrometer instruments have a reading accuracy of 0.01 mm.

Smooth micrometers are designed for measuring the external dimensions and lengths of smooth parts. According to the standard, micrometers are produced with the following measurement limits: 0-25, 25-50, 50-75, 75-100 and then after 25 mm to 275-300 mm, and then 300-400, 400-500 and 500-600 mm.

All micrometers have a maximum micrometer screw travel of 25 mm, which helps maintain the required accuracy. With longer screws, accuracy would be lower due to the accumulation of errors during screw manufacturing. The last three types of micrometers with a difference in measurement limits of 100 mm also have a screw stroke of 25 mm, and an increase in measurement limits is achieved through the use of replaceable heels.

Rice. 18.

The micrometer (Fig. 18) consists of a bracket 1, into which a fixed heel 2 is pressed on one side, and a stem 5 on the other. The stem has a thread inside into which a micrometer screw 3 is screwed. The screw is fixedly attached to the drum 6, to the end of which it is screwed ratchet body 7. When the ratchet rotates, the drum and micrometer screw rotate. The ratchet serves to ensure a constant clamping value of the parts being measured and, therefore, measurement accuracy. The screw is secured in a certain position using stopper 4.

A line is drawn on the stem along its axis, on both sides of which there is a scale, where whole millimeters are indicated on one side, and half millimeters on the other side. On the conical part of the drum there is a circular scale with 50 divisions. The pitch of the micrometric screw is 0.5 mm, i.e., per one revolution the screw moves by 0.5 mm, and when turning the drum by one division, the longitudinal movement will be 0.5: 50 = 0.01 mm. Dimensions are measured using a scale on the stem (whole millimeters and half millimeters) and a scale on the drum (hundredths of a millimeter). Those divisions on the stem that are to the left of the beveled edge of the drum, and those divisions on the drum that coincide with the longitudinal line on the stem are counted.

Before taking measurements, check the zero positions of the micrometer. To do this, use a ratchet to move the micrometer screw until it comes into contact with the fixed heel within the measurement range of 0-25 mm or with the setting standard at other measurement limits. The size of the setting standard must be equal to the lower measurement limit of the micrometer. In this case, for a working micrometer, the zero line of the drum should coincide with the longitudinal line of the stem, and the edge of the drum should coincide with the zero line of the stem scale.

A micrometric bore gauge (stihmass) is used to measure the internal dimensions of holes, grooves, and staples. It is produced with measurement limits of 50-75, 75-175, 75-600, 150-1250, 860-2500, 1520-4000 mm. The measurement limit is increased by using extension cords. A micrometer bore gauge consists of a micrometer head with measuring tips and a set of extensions. The bore gauge differs from a micrometer in the absence of a bracket and ratchet, as well as some design features. A micrometric depth gauge is used to accurately measure the depth of holes, grooves, grooves, and recesses. It is produced with measurement limits of 0-25, 0-50, 0-100 mm. Reading accuracy 0.01 mm. The maximum stroke of the micrometric screw is 25 mm. Expansion of measurement limits is achieved by using replaceable rods.

A micrometer is a universal measuring device that is designed to obtain the linear dimensions of the part being measured. Regardless of whether the relative or absolute measurement principle is used here, they are all produced by the contact method. The scope of measurements for almost all instruments lies in the area of ​​​​relatively small sizes, since the micrometer itself works with high accuracy, down to thousandths of a millimeter. Depending on the model used, the error can range from 2 to 50 microns. A micrometer is being created in accordance with GOST 6507 90.

micrometers:photo

The scope of application of the device is very wide, as it is very convenient and practical. It is often small in size, therefore, it can be used both at home and in quality control laboratories, tool workshops, mechanical engineering, carpentry and plumbing workshops. They are used to control the thickness of wires, walls of parts, metal sheets, and so on. Few measuring instruments can operate in such a range with a given accuracy.

Despite the variety of models, each of which is intended for specific purposes, their operating principle turns out to be very similar. It is based on the movement of a screw, which is located along the axis of the device in a nut fixed motionless. The movement is made in proportion to the angle it passes around the axis. A full revolution is displayed on a scale located on the stem. It shows 1mm of distance traveled. The beats are shown on the drum, which shows the data with an accuracy of 0.01 mm. Depending on the specific model, there may be some differences in the data.

The kit often includes standards against which the device can be verified before use. Each range uses its own standards, because the measurement limits of a micrometer can differ several times.

Advantages and disadvantages

It is not for nothing that the micrometer has become one of the most common means for obtaining ultra-precise linear dimensions of parts. The micrometer pitch of 0.01 mm allows the micrometer to be used in a wide variety of applications. Thanks to its small size, it is easy to carry and can always be at hand. Like other mechanical devices, if properly cared for, it can last a very long time. It is easy to calibrate, which should preferably be done before each use. Some modern models can immediately connect to a computer to enter measurement data, simplifying further calculations.

The difficulty lies in reading the data, since not every person knows how to use a micrometer correctly. There are three scales here, each of which shows its own data, so they need to be added to get the final result. Any micrometer has a limited range of use, which also creates difficulties in use, therefore, sometimes you have to have several devices when it comes to production. The complex design and many parts, although they will improve accuracy and reduce errors, make them practically unrepairable.

Types of micrometers

There are several types of devices that differ in their scope of application, and accordingly have some distinctive features that are more suitable for a particular type of activity. Among them are:

• Gear measuring (micrometer MZ) - it works with teeth located on gears and serves to determine the normal length of a tooth, the modulus of which starts from 1 mm. The upper limit is 50 mm. The kit includes an installation plane-parallel final length measure;

• Pipe micrometer - it is used to determine the linear dimensions of walls in pipes. This is relevant both for quality control during manufacturing and for studying the wear of products;

• Sheet (ML) - used for measuring the thickness of films and sheets. They generally work with fairly small dimensions and have a very high accuracy class;

• Smooth micrometers GOST 6507 90 are the most common type of products that are used in most areas and are used to determine the linear external dimensions of all available parts;
• Lever type (LR) are measuring instruments that have built-in lever-geared indicator devices. This system has high mechanical complexity and consists of many parts. But this greatly simplifies the process of use, therefore, they are used in places where intensive measurement of various parts takes place. The read data is transmitted to the indicator head and displayed on the scale;

• Wire gauges (WM) - they are used to measure diameters in wires, bearings and balls. Not every type can work normally with round objects, but in this case the design features predispose to this;

• Prismatic (MIT, MPI MSI) - they are used for measuring blade tools with three, five and seven working blades from http://www.classeng.com, respectively. The heel of the staple in these devices is made in the form of a standard prism;

• Groove micrometers (MCN) - micrometers of this type work by determining the distance between parallel grooves and determining the width of each of them. The upper limit of the devices is 50 mm. The kit includes an installation plane-parallel final length measure;
• Thread gauges (MVM, there are both metric and inch micrometers) - they have special pegs inserts in their design;

• Universal (MKU) - devices that have seven pairs of interchangeable heels. Thanks to the presence of a replaceable set, it is possible to measure parts with different configurations;
• For deep measurements (MCG);
• Limit or two-scale (MCP) - used to measure maximum external dimensions;
• For hot rolling (HRP)
• Tabletop - stationary micrometers that are attached to the work table;
• Micrometer for left-handers.

General classification

In general, all measuring instruments of this type can be classified according to the following characteristics and parameters:

• Types of micrometers;
• Lower and upper limit of measurement;
• Dimensions;
• Principle of data display (mechanical or electronic);
• Device accuracy class;
• Scope of application;
• Purpose;
• Design features (tabletop or handheld);
• The presence or absence of additional devices.

Specifications

Designation of micrometers and their interpretation

Micrometers often have designations that combine letters and numbers. This helps to determine certain characteristics from the model name alone. For example, the first letters (let's say MK) indicate the type of micrometer (in this case, a smooth micrometer). The presence of the letter “H” indicates that the counting is carried out on two scales on the stem and on a drum with a vernier. If there is a letter “C”, this means that this is a digital type device and all measurement results will be shown on a special display. When there is a two-digit number, it indicates the final value related to the measured range, and the number after the dash indicates the accuracy class.

Manufacturers

Many devices have been in operation since the times of the USSR, but they are mainly in private use. Nowadays you can find models from various manufacturers in stores. These can be both domestic and foreign companies. Those who deal with electronic devices are very promising. The most common are:

• Microtech (Ukraine, Kharkov);
• Standard Gage;
• AmPro (Taiwan);
• Mitutoyo (Japan);
• Schut Geometrical Metrlogy (Netherlands);
• Topex;
• JTC (Taiwan);
• Standard (Russia);
• IsoMaster;
• Tesamaster.

Micrometer:Video

Pavlodar State University

them. S. Toraigyrova

Faculty of Metallurgy, Mechanical Engineering and Transport

DEVICE

AND OPERATION OF MICROMETRIC INSTRUMENTS

methodological instructions for performing laboratory work in the disciplines “Methods and means of measurement and control”, “Standardization, certification and technical measurements”, “Fundamentals of interchangeability”, Metrology”

for students of mechanical engineering specialties

(for intra-university use)

Pavlodar

UDC 621: 531.714(07)

BBK 34.63-5ya7

U82

Reviewer:

Candidate of Technical Sciences, Professor

master, senior lecturer

Compiled by:

U82 Design and operation of micrometric instruments: guidelines for performing laboratory work in the disciplines “Standardization, certification and technical measurements”, “Methods and means of measurement and control”, “Fundamentals of interchangeability”, “Metrology” for students of mechanical engineering specialties (for intra-university use) /comp. , – Pavlodar, 2007. – 17 p.

In the guidelines, in order to gain an understanding of micrometric instruments based on operation and design, and using a specific example, students are asked to give an opinion on the suitability of the part with a determination of the metrological characteristics of the micrometric instruments used.

Laboratory work is an integral part of the general cycle of laboratory work provided for in the disciplines “Standardization, certification and technical measurements”, “Methods and means of measurement and control”, “Fundamentals of interchangeability”, “Metrology”.

UDC 621: 531.714(07)

BBK 34.63-5ya7

© Pavlodar State University named after. S. Toraigyrova, 2007

Micrometric instruments are widely used in mechanical engineering in the process of manufacturing and monitoring parts with an accuracy of 0.01 mm. The error in monitoring the manufacture of a part largely depends on the degree of wear and metrological parameters of micrometric tools. Therefore, it is necessary to know and be able to configure and adjust micrometer instruments for accurate measurements.

The laboratory work aims to familiarize students with the purpose, structure, application, setup, adjustment and variety of micrometric instruments.

In laboratory work, students need to give a conclusion about the suitability of the part and determine the metrological indicators of the micrometric instruments used when measuring the dimensions of the part.

1 Purpose and objectives of laboratory work

1.1 Purpose of laboratory work– to gain an understanding of micrometric instruments based on their operation and design and using a specific example, students are asked to give an opinion on the suitability of the part with the definition of metrological indicators used by the micrometric instruments.

1.2 Objectives of laboratory work:

Study this guideline;

Using the formulas given in the guidelines, determine the metrological indicators of micrometric instruments;

For a given part, draw a sketch indicating on it the dimensions to be measured, and also decipher the symbolic designations of tolerances;

To make a report.

2 Basic provisions

Micrometric measuring instruments include: micrometers for external measurements; micrometers for internal measurements - weights and micrometric depth gauges. All of these instruments use a micrometer head as a measuring device.

Micrometric heads of the most common designs are shown in Figure 1. For all heads, the right end of stem 2 ends with a split sleeve with internal cylindrical and external conical threads. A microscrew 4 is screwed into the internal thread of the stem, the left smooth part of which fits into the same smooth hole in the stem, which ensures the exact direction of the microscrew. The microscrew has a measuring plane on the left, and on the right - a shaped cylindrical or conical shank 5, onto which a drum 5 is placed, connected to the microscrew by an installation cap 7 or a conical split ring 9, secured by a moving nut 10. Markings are applied on the beveled edge of the drum along its entire circumference . The installation cap is made integral with the ratcheting device 15. When the head 13 rotates, torque is transmitted to the microscrew, but as soon as the measuring force at the end of the microscrew exceeds the force that can be provided by the spring resistance force, tooth 12 will immediately begin to slip relative to the gear track of the head 13 , and it will spin idle. A conical nut 6 is screwed onto the external conical thread of the stem, with which you can tighten the internal thread of the bushing and thereby regulate the axial play of the microscrew relative to the nut that occurs during thread wear.

1 - bracket; 2 - stem; 3 - bushing; 4 - microscrew; 5 - drum; 6 - adjusting nut; 7 - connecting cap; 8 - shank; 9 - conical split ring; 10 - clamping nut; 11 - spring of the ratchet device; 12 - tooth of the ratchet device; 13 - head of the ratchet device; 14 - screw; 15 - ratchet device; 16 - stopper lever; 17 - stopper axis; 18 - stopper ring; 19 - spring split ring.

Figure 1 – Micrometer heads

The locking device of the micrometer head, shown in Figure 1, a, is made in the form of an eccentric axis 17 connected to the lever 16. If you turn the lever to the left until it stops, the microscrew will be pressed against the stem body. In Figure 1, b, the locking device is made in the form of a ring 18, which is screwed onto the left end of the split conical bushing. In the micrometer head shown in Figure 1c, the drum 5 is attached to the microscrew by pressing the drum shoulders to the cylindrical shank of the microscrew 8 through a split conical washer 9 using a nut 10. The outer ring 18 of the locking device is inserted into the bracket body. If you turn this ring clockwise, its oblique cut will press the roller against the spring shank, causing the inner split ring 19 to compress and lock the microscrew.

The reading accuracy of all micrometer heads is 0.01mm.

Micrometers for external measurements. Any micrometer has a bracket 1 (Figure 2), on the left end of which a rigid heel 2 is pressed in or, if the measurement limits are more than 300 mm, replaceable elongated heels (Figure 3). The heels are installed using a gauge. At the right end of the bracket there is mounted a micrometer head 6 (Figure 2), consisting of a stem 5, a drum and a movable heel 4 connected to a microscrew. The drum is connected to the installation cap 7 and the ratchet device 8. To fix the size obtained during measurement, the microscrew is locked with the lever of the brake device 9.

When measuring, an object is inserted between the heels of the micrometer and, by rotating the drum by the head of the ratcheting device 5, the movable heel 4 is brought into contact with it. After the head of the ratchet device begins to rotate, the readings are taken. Micrometers have measurement limits from 0 to 600mm with an interval of 25mm (up to 300mm) and with an interval of 100mm (after 300mm).

Before measurements, the micrometer must be checked to ensure that the zero lines on the stem and the drum match. If the zero lines do not match, then the micrometer must be adjusted. The micrometer is adjusted in the following order.

Turn the locking lever 16 (Figure 1, a) or the locking ring 18 (Figure 1, b and c) and release (unlock) the microscrew.

1 - bracket; 2 - hard heel; 3 - gauge (gauge measure) for setting the micrometer to zero; 4 - movable heel (microscrew); 5 - stem; 6 - micrometer head; 7 - installation cap; 8 - ratchet device; 9 - brake device.

Figure 2 – Micrometer for external measurements

Figure 3 – Attaching the heels

Create a gap of 1 mm between heels 2 and 4 (Figure 2) or, if an end block 3 is inserted between the heels (Figure 2), between the end of the end block and the heel 4.

Rotate the drum by the head of the ratcheting device 5, bringing the heels 2 and 4 into contact. The moment of contact is detected by the characteristic sound of the ratcheting device. In this position, check the coincidence of the zero stroke on the drum with the zero stroke on stem 5. If the zero strokes coincide, the micrometer is ready for use, but if not, then it needs to be adjusted. In this case, the following operations are performed.

Using the brake device lever 9 (Figure 2) or ring 18 (Figure 1), the microscrew is locked.

In this position, the drum 6 (Figure 2) is disconnected from the microscrew of the heel 4. To do this, holding the drum with your left hand, loosen the connecting cap 7 with your right hand. As a result of this, the drum can rotate freely around the stem and it can be set to zero.

Having set the drum to zero, carefully tighten (attach) the connecting cap 7.

Having released the stopper and separated the measuring heels from each other or from the installation gauge, the connecting cap is finally secured. After this, repeat the first three operations again to check the installation.

Micrometric bore gauges (gauges) are used to measure hole diameters or internal dimensions greater than 50 mm. The micrometric bore gauge consists of a head (Figure 4, a) and extensions (Figure 4, b). The head includes the micrometer screw 5 itself, a stem 3 with a threaded left end, onto which extensions or a safety nut 2 are screwed, spherical tips 1 and 10, which are in contact with the walls of the object being measured, a locking screw 4, a drum 7 and an installation cap 9. Name size micrometric bore gauge will be when the zero division of the scale of drum 7 coincides with the initial stroke of the longitudinal scale on stem 3.

In most bore gauges, the smallest size is 75mm or more. The largest size depends on the number of extensions connected to the head and their sizes. To reduce measurement errors, it is necessary to use no more than 3–4 extension cords. To connect the extension to the micrometer head, you need to unscrew the safety nut 2 and screw in the right end of the extension instead. When screwing the measuring tip 1, pressing on the right end of the extension (Figure 4, b), forces its left measuring end to come out. When the head is unscrewed, the steel rod (stichmass), under the influence of spring 12, is again hidden in the metal tube 14. Another extension can be screwed onto the free end of the threaded extension, etc. A safety nut can be screwed onto the free end of the last extension.

1 – spherical tip 9 – installation cap

2 – safety nut 10 – spherical tip

3 – stem 11 – collar

4 – locking screw 12 – spring

5 – microscrew 13 – safety head

6 – adjusting nut 14 – safety tube

7 – drum 15 – extension

8 – split ring

Figure 4 – Micrometric bore gauge

During the measurement process, the inside gauge is inserted into the hole and one end is pressed against the surface of the object being measured, and the other, by rotating the drum, is brought into contact with the opposite surface. By rocking the inside gauge first in the axial and then in the diametrical directions, the smallest and largest dimensions are found. Having fixed the size using a stopper and removing the bore gauge from the hole, a reading is made. When using extensions, it is necessary to screw them onto the head, starting with larger sizes, since a different sequence of installing extensions leads to an increase in measurement error.

The zero setting of the bore gauge head is checked using end gauges or a special bracket attached to the bore gauge.

Checking and adjusting the weight is carried out in the following order.

Insert the micrometer head with the safety nut 2 on it into the bracket .

Having unstopped microscrew 4 and holding the micrometer head in the bracket with your left hand, turn drum 7 with your right hand until tips 1 and 10 come into contact with the side walls of the bracket. The microscrew is locked in this position.

Take out the micrometer head and, holding the drum 7 with your left hand, loosen the cap 9 with your right hand. In this position, the drum easily rotates around the stem 3 and can be installed so that its zero line coincides with the zero line of the stem.

Easily tighten cap 9, unfasten it and tighten it completely. The head is configured and ready to go.

A micrometric depth gauge (Figure 5) is used to measure the depth of holes, ledges, recesses, etc. In depth gauges, the stem is not connected to a bracket, like with micrometers, but to a base (traverse) 1. In addition, unlike micrometers, the zero of the main micrometric scale The depth gauge heads are located not on the left, but on the right. In all other respects, the depth gauge head is similar to the micrometer head. A hole 10 is made at the lower end of the microscrew, into which a cylindrical rod 11 of the required length can be inserted. The length of the rod depends on the size being measured. At the end of each cylindrical rod there is a spring device that ensures sufficient connection between the rod and the microscrew. Replacement rods are available in four sizes: 0-25; 25-50; 50-75; 75-100mm.

Checking and adjusting the micrometric depth gauge is carried out in the following order.

Turn out the drum 5 of the micrometer head so that the end of the measuring rod disappears into the hole in the traverse.

Place the traverse on the surface plate and, pressing it with your left hand, rotate the head of the ratcheting device 8 with your right hand until clicks appear. In this position, microscrew 3 is fixed using locking screw 9.

Holding drum 5 with your left hand, loosen cap 7 with your right hand. In this position, the drum easily rotates around the stem and can be installed so that its zero stroke coincides with the zero stroke of the stem.

Wrap cap 7 and unlock the microscrew. The device is ready for use.

1 – base (crossbeam)

2 – stem

3 – microscrew

4 – adjusting nut

5 – drum

6 – screw shank

7 – installation cap

8 – ratcheting device

9 – locking screw

10 – hole for installing the rod

11 – rods

Figure 5 – Micrometric depth gauge

3 Work order

The initial data when carrying out measurements with micrometer instruments are dimensions, each of which is intended only for the use of a single device.

3.1 Study the design, adjustment and adjustment of micrometer instruments.

3.2 Give a sketch of the part, indicating the specified dimensions on it.

3.3 Decipher the symbolic designations of tolerances for all given dimensions.

3.4 Determine the following metrological indicators for all tools:

a) measurement limits;

b) the division price on the stem of the micrometer head in mm;

c) the division price on the drum in mm. The division price on the drum is found using the formula

e=t/n (1)

where t is the thread pitch of the microscrew

n – number of divisions on the drum;

d) the possible maximum error Δlim of the instrument within the limits of its use (see Appendix A).

3.5 Check and configure all instruments.

3.6 Measure all specified dimensions, taking into account the capabilities of the tool. Write down the measured size taking into account the maximum error

Ddel=Dpr±ΔΣ(measured) (2)

where Dweight is the possible size taking into account the measurement error

Dpr – size established according to instrument readings

ΔΣ(measured) – maximum error of the device for the obtained size.

3.7 Give an opinion on the suitability of the product (whether the resulting size fits within the tolerance).

4.1 Purpose of the work

4.2 Sketch of the part indicating on it the dimensions to be measured and a symbolic explanation of the tolerance symbols

4.3 Metrological indicators of the micrometric instruments used

4.4 Conclusion on the suitability of the part

5 Security measures

5.1 It is prohibited to perform actions that could lead to injury, aimless rotation of screws, verniers, etc.

5.2 Be careful when touching sharp edges of the part; in case of a cut, contact a teacher.

Control questions

1 Types, design and purpose of micrometric instruments

2 Metrological indicators of micrometric instruments

3 Adjustment and adjustment of micrometer instruments

4 Maximum error of micrometric instruments

5 As directed by the teacher, decipher the symbolic designation of tolerances

Literature

1, Poleshchenko on interchangeability, standardization and technical measurements. M.: Kolos, 1977. – 224 p.

2, etc. Interchangeability, standardization and technical measurements: Textbook - 5th ed., M.: Mechanical Engineering, 19 p.

3 Tolerances and fits. Directory in 2 volumes. /Edited, 6th ed. - L.: Mechanical Engineering, 19 p.

Appendix A

(informative)

Limit errors of instruments for measuring linear quantities (±Δlim)

Name of measuring instrument

contact

Size intervals, mm

Division value, mm

Lever micrometers are in your arms

are in the rack

Value, Δlim, µm

Micrometric depth gauges with the absolute method

at relates method

Moving the rod

Installation Tools

Rough class. pov details

Size intervals, mm

Value, Δlim, µm

Micrometric bore gauge with division value 0.01mm

according to the installation measure

Introduction……………………………………………………. Goals and objectives of laboratory work……………………… Purpose of laboratory work………………………………… Objectives of laboratory work……………………………………………………… Basic provisions……………………………………………………….. Procedure of work……………………………….. Security measures…………………………………………. Control questions……………………………………… Literature…………………………………………………… Appendix A…………………………………………………………….. I APPROVED Vice-Rector for SD PSU named after S. Toraigyrova (personal signature) "____"____________2007 Compiled by: Senior Lecturer __________ Senior Lecturer __________ Department of Mechanical Engineering and Standardization Approved at the meeting of the department “____”______2007. Protocol No._____ Head of the department _________________ Approved by the methodological council of the Faculty of Metallurgy, Mechanical Engineering and Transport “____”_________2007. Protocol No._____ Chairman of the MS _____________________ AGREED Dean of the Faculty _____________ “___”_______2007 OMK normative inspector _________ “___”______2007 OPiMO APPROVED Head of OPiMO _____________ “___”______2007 Review for methodological instructions for laboratory work “Design and operation of micrometric instruments” in the disciplines “Metrology”, “Fundamentals of interchangeability”, “Standardization, certification and technical measurements”, “Methods and means of measurement and control”. The methodological instructions present the devices, purpose and use of micrometric instruments - micrometers, micrometric depth gauges and micrometric bore gauges, as well as their regulation and adjustment. For each instrument described, pictures with explanatory text are presented. According to the given theoretical provisions, the student acquires the skills of reading a drawing of a part, the correct choice of measurement methods and the use of measuring tools. The guidelines were developed in accordance with the general requirements for design and publication at the Scientific Publishing Center of PSU named after. S. Toraigyrov according to MI PGU 4.02.1-05. The methodological instructions have been developed to help students to fully and clearly master the lecture material in practice. Considering the practical significance of this laboratory work “Design and operation of micrometric instruments” for students of mechanical engineering specialties, it is recommended for publication at the Research Center of PSU named after. S. Toraigyrova. Master, senior lecturer Review for methodological instructions for laboratory work “Design and operation of micrometric instruments” in the disciplines “Metrology”, “Fundamentals of interchangeability”, “Standardization, certification and technical measurements”, “Methods and means of measurement and control”. The guidelines have been compiled with the aim of obtaining an idea of ​​micrometric instruments. In the process of performing laboratory work on a specific part, students are asked to give an opinion on the suitability of the part, determining the metrological indicators of the micrometric instruments used. When making a conclusion about the suitability of a part, the maximum error of micrometric instruments is taken into account, which gives a complete picture when measuring the dimensions of a part. Laboratory work is provided for further development of theoretical material in the disciplines “Standardization, certification and technical measurements”, “Methods and means of measurement and control”, “Fundamentals of interchangeability”, “Metrology”. Considering the practical significance of this laboratory work “Design and operation of micrometric instruments” for students of mechanical engineering specialties, it is recommended for publication at the Research Center of PSU named after. S. Toraigyrova. Candidate of Technical Sciences, Professor