Means for measuring angles and cones

The main parameter controlled when processing corners and cones is flat angle, the unit of which is taken to be a degree. A degree is 1/360 of a circle; it is divided into 60 minutes of arc, and minutes are divided into 60 seconds of arc.

Methods for measuring angles can be divided into 3 main types:

1. Comparison method with rigid angle measures or templates.

2. Absolute method, based on the use of measuring instruments with an angular scale.

3. Indirect method, which consists of measuring linear dimensions related to the cone angle by trigonometric relationships.

The simplest tools for checking angles are squares with an angle of 90 0, designed for marking and checking the mutual perpendicularity of individual surfaces of parts during equipment installation and for monitoring tools, instruments and machines. In accordance with the standard, there are 6 types of squares (Fig. 2.12.):

More universal tools for control and marking of angles - protractor inclinometers (simple, optical, universal). In mechanical engineering, inclinometers with a vernier type UN are widely used to measure external and internal corners and type UM for measuring only external angles (Fig. 2.13.).

For methods of measuring angles, see Fig. 2.14.

Calibers used to control the dimensions of holes and external surfaces of parts. In manufacturing, it is not always necessary to know the actual size. Sometimes it is enough to make sure that the actual size of the part is within the limits established tolerance, i.e. between the largest and smallest size limits. In accordance with these dimensions, limit gauges are used, which have two (or two pairs) measuring surfaces of the go-through and non-go-through parts. There are smooth, threaded, conical, etc. gauges. Plug gauges, staple gauges, depending on the size of the parts being controlled, the type of production and other factors, have different structural forms(Fig. 2.15, Fig. 2.16).

The pass side (PR) of the plug or staple has a size equal to the smallest limit size of the hole or shaft, and the non-pass side (NOT) has a size equal to the largest limit size of the shaft and, accordingly, the hole. Methods of measuring with plug gauges and clamp gauges are shown in Fig. 2.16.

Cone gauges tools are plug gauges and bushing gauges. Control of instrumental cones is carried out using a complex method, i.e. simultaneously check the cone angle, diameters and lengths (Fig. 2.17).

Templates used to check complex part profiles and linear dimensions. Templates are made from sheet steel. Inspection is carried out by mating the template with the surface being tested. The quality of processing is judged by the size and uniformity of the lumen (Fig. 2.18., Fig. 2.19.).

Thread control Depending on the type (profile) and accuracy, it is carried out using various control and measuring equipment.

Threaded templates to determine the thread pitch and profile, they are sets of steel plates fixed in a holder with precise profiles (teeth) of metric and inch threads. Each plate is labeled with pitch values, thread diameters, or threads per inch.

Radius templates are used to measure the deviation of the dimensions of convex and concave surfaces of parts (Fig. 2.18.). To measure the depth of the grooves, the height and length of the ledges, limit gauges-templates are used that work against the light. They also have two sides and are designated B (for bigger size) and M (for smaller sizes). In Fig. 2.19. templates for checking the length, width and height of tabs and grooves are shown various methods: “through the light”, “by pushing” and “by the scratch method”.

Thread gauges(plugs and rings) are used to control internal and external threads (Fig. 2.20.).

Thread micrometers with inserts are used to measure the average diameter of a triangular external thread.

Inserts are selected in accordance with the pitch of the thread being measured from the set available in the case for the micrometer (Fig. 2.21.). Reading the micrometer is done in the same way as when measuring smooth cylindrical surfaces.

Thread control can also be carried out with a micrometer using three measuring wires (Fig. 2.22.). With this method, the distance M is measured between the protruding points of three wires placed in the recesses of the thread, then the average diameter d 2 of the thread is determined through mathematical transformations.

The wire diameter dpr is selected from the table depending on the thread pitch. Two wires are installed in the depressions on one side, and the third - in the opposite cavity (Fig. 2.22.)

Average diameter metric thread d 2 = M – 3 d pr + 0.866 R

Average diameter of inch thread d 2 = M – 3.165 d pr + 0.9605 R

Plane-parallel gauge blocks are used to transfer the size of a unit of length onto a product (when marking), checking and adjusting measuring instruments (micrometers, caliber of staples and other measuring instruments), directly measuring the dimensions of products, fixtures, when setting up machines, etc.

One of the main properties of gauge blocks is adhesiveness, the ability to firmly connect to each other when one gauge is applied and pushed onto another with some pressure, which is achieved due to the very low roughness of the measuring surfaces. End gauges are supplied in a set with a quantity of 7…12 tiles (Fig. 2.23).

The most widely used sets are those consisting of 87 and 42 gauge blocks. Each tile reproduces only one size, which is marked on one of its sides. For ease of use of gauge blocks, sets of accessories are produced for them (Fig. 2.24.), which include: bases - 5, plane-parallel, radius - 2, scribers - 3, center sides - 4, holders - 1 for attaching blocks of gauge blocks with sides. The compilation of a block of gauge blocks is carried out in accordance with the class or category of tiles and the sizes of tiles available in this set.

Initially, a smaller tile is selected, the size of which includes the last decimal place, etc. Let's say you need to assemble a block of gauge blocks measuring 37.875 mm from a set consisting of 87 tiles:

1 tile 1.005 mm, remainder 36.87

2 tiles 1.37 mm, remainder 35.5

3 tiles 5.5 mm, balance 30.00

4 tiles 30 mm, remainder 0.

The block amount is 1.005+1.37+5.5+30 = 37.875.

In the same way, a block is assembled from a set of 42 tiles.

1,005+1,07+4,00+30 = 37,875.

Methods for measuring with plane-parallel gauge blocks of length and marking using accessories are shown in Fig. 2.25.

Angular prismatic measures (tiles) are intended for checking and adjusting measuring angle measuring instruments and tools, as well as for direct measurement of external and internal angles of parts with high density. Angle measures perform the same role when measuring angles,

same as gauge blocks when measuring length. To working sides angular measures have the same requirements as for end measures, i.e. ensuring adhesion (fitness).

Angle measures are produced in sets with a quantity of 7...93 tiles in each (Fig. 2.26.). Checking the corners with tiles is carried out “through the light”.

To increase the strength of a block assembled from corner tiles, they are supplied with a set of accessories, which include ties, screws, wedges and others (Fig. 2.27.). The block is strengthened through special holes in the tiles.

The rules for calculating angular measures for the formation of blocks, as well as the rules for preparing for assembly and assembling them into a block, are similar to the rules used in the preparation of end length measures.

Methods of measuring with angular measures are shown in Fig. 2.28.

Objects of angular measurements vary in size, measurement angles and required measurement accuracy. This requires a wide variety of methods and means for measuring angles, which are grouped into three groups:

first group of methods and funds combines measurement techniques using “rigid measures” - squares, corner tiles, polyhedral prisms;

second group form goniometric methods and measuring instruments, in which the measured angle is compared with the corresponding value of the subdivision of a circular or sector scale built into the device;

third group– a group of trigonometric tools and methods differs in that the measure with which the measured angle is compared is the angle of a right triangle.

Prismatic Angle Measures They produce several types: tiles with one working angle, four working angles, hexagonal prisms with uneven angular pitch.

Corner tiles are produced in the form of a set of tiles, selected in such a way that they can be used to make blocks with angles ranging from 10° to 90° (accuracy classes 0, 1 and 2). Manufacturing error ±10´´ - first class, ±30´´ - second class.

The principle of the goniometric measurement method is that the product being measured (abc) is rigidly connected to an angular measure - a circular scale (D). In a certain position relative to any plane (1), a reading is taken from a fixed pointer (d), then the scale is turned to a position where the side (bc) of the angle coincides with the plane in which the side (ab) was located before the rotation or with another plane , parallel to it. After this, the countdown is carried out again according to the pointer. In this case, the dial will rotate by an angle (φ) between the normals to the sides of the angle, equal to the difference in readings before and after rotating the dial. If the measured angle is β, then β=180 o – φ.

Measurement

Measurement - finding value physical quantity experimentally using special technical means.

There are four types of scales:

Name scale– is based on attributing numbers (signs) to an object.

Order scale– involves the ordering of objects relative to some specific property of them, i.e. their arrangement in descending or ascending order. The resulting ordered series is called ranked, and the procedure itself – ranking.

Interval scale– first sets the unit of physical quantity. The difference in values ​​of a physical quantity is plotted on the interval scale, while the values ​​themselves are considered unknown. For example, the Celsius temperature scale - the beginning is taken at the melting temperature of ice, and the boiling point of water is 100 o and the scale extends both towards positive and towards negative temperatures. On the Fahrenheit temperature scale, the same interval is divided into 180 degrees and the beginning is shifted 32 degrees to the side low temperatures. Dividing the interval scale into equal parts is a gradation that establishes a unit of physical quantity, which allows it to be measured numerically and to estimate the measurement error.

Relationship scale– is an interval scale with a natural beginning. For example, on the Celsius scale, you can count the absolute value and determine not only how much the temperature T 1 of one body is greater than the temperature T 2 of another body, but also how many times more or less according to the rule.

In the general case, when comparing two physical quantities X with each other according to this rule, the values ​​of n, arranged in ascending or descending order, form a scale of ratios and cover the range of values ​​from 0 to ∞. Unlike the interval scale, the ratio scale does not contain negative values. It is the most perfect, the most informative, because... Measurement results can be added, subtracted, divided and multiplied.

The horizontal angle is measured using a method. When measuring several angles that have a common vertex, the circular method is used.

Work begins by installing a theodolite over the center of the sign (for example, a peg), securing the top of the corner, and sighting targets (milestones, special marks on tripods) at the ends of the sides of the corner.

Installation of theodolite in working position consists of centering the device, leveling it and focusing the telescope.

Centering performed using a plumb line. Place the tripod over the peg so that the plane of its head is horizontal and the height corresponds to the height of the observer. Fix the theodolite on a tripod, hang a plumb line on the hook of the mounting screw and, having loosened it, move the theodolite along the head of the tripod until the tip of the plumb line aligns with the center of the peg. Centering accuracy with a thread plumb line is 3 – 5 mm.

Using an optical plummet of a theodolite (if the theodolite has one), you must first perform leveling and then centering. The centering accuracy of the optical plummet is 1 – 2 mm.

Leveling Theodolite is performed in the following order. By turning the alidade, set its level in the direction of the two lifting screws, and by rotating them in different directions, bring the level bubble to the zero point. Then the alidade is rotated 90º and the third lifting screw again brings the bubble to the zero point.

Focusing The telescope is performed “by the eye” and “by the object”. By focusing “by the eye”, by rotating the diopter ring of the eyepiece, a clear image of the reticle is achieved. By focusing “on the subject” and rotating the ratchet handle, a clear image of the observed object is achieved. Focusing must be done so that when the observer's head shakes, the image does not move relative to the strokes of the grid of threads.

Measuring an angle using a method. The reception consists of two half-receptions. First half move performed with the vertical circle positioned to the left of the telescope. Having secured the limb and unfastened the alidade, point the telescope at the right sighting target. After the observed sign has fallen into the field of view of the telescope, the fixing screws of the alidade and the telescope are clamped and, using the aiming screws of the alidade and telescope, the center of the grid of threads is aimed at the image of the sign and a reading is taken in a horizontal circle. Then, having detached the tube and alidade, point the tube at the left sighting target and take the second reading. The difference between the first and second readings gives the value of the measured angle. If the first reading is less than the second, then 360º is added to it.

The second half-reception is performed with the vertical circle positioned on the right, for which the pipe is moved through the zenith. To ensure that the readings differ from those taken in the first half-reception, the dial is shifted by several degrees. Then the measurements are performed in the same sequence as in the first half-step.

If the results of measuring the angle in half-measures differ by no more than double the precision of the instrument (that is, 1¢ for theodolite T30), calculate the average, which is taken as the final result.

The concept of measurement using circular techniques several angles that have a common vertex. One of the directions is taken as the initial one. Alternately, clockwise, with a circle on the left, point the telescope at all sighting targets and take readings. The last pointing is again done in the initial direction. Then, having moved the pipe through the zenith, all directions are observed again, but in reverse order- counterclock-wise. From the readings of the circle on the left and the circle on the right, the averages are found and the average value of the initial direction is subtracted from them. Get a list of directions - angles measured from the initial direction.

Angle measures (end, sheet, prismatic, squares, templates, gauges);

Goniometer instruments (bevel goniometers, optical goniometers, goniometer heads, levels, goniometers, theodolites, dividing heads and tables, autocollimators);

Devices for indirect measurements - trigonometric devices (sine rulers, cone meters);

Test equipment

These are special production tools for monitoring objects, representing a constructive combination of basing, clamping and control and measuring devices (elements).

The main requirements for them: the necessary accuracy and performance. In addition, they must be easy to use, technologically advanced to manufacture, wear-resistant and economical.

Testing devices are divided into the following signs:

According to the principle of operation and the nature of the control and measuring devices used (with a reading device - scale with dial indicators, pneumatic meters, etc.), with the help of which they determine numeric values controlled quantities; scale-free (limit) using gauges, probes, etc., which serve to separate parts into good and defective (defect – “plus”, “defect – “minus”); combined (electrical contact sensors with a reading scale, etc.), which make it possible not only to separate parts into good and defective, but also to evaluate the numerical values ​​of the controlled parameters;

By size and weight (stationary and portable);

By the number of controlled parameters (one- and multidimensional);

By stage technological process(operating, acceptance);

By built-in technological equipment(built-in and non-built-in);

By direct participation in the technical process (for control directly during the manufacturing process of the product - active and control control; outside the manufacturing process);

By stage of the technical process (to monitor the correctness of setup, to monitor the correctness of the technical process, for statistical control).

The total error of such devices should not exceed 8 - 30% of the tolerance of the controlled parameter: for critical products, for example, aviation equipment - 8%, for less critical ones - 12.5...20%, for others - 25...30%.

FEATURES OF KEY WORKERS

MEASURING MEANS

Measures of length and angles

Working measures are divided according to design features into line And end.

Lined working measures of length include measuring rulers, which are, as a rule, metal strips on the planes of which scales are applied. They produce rulers for measuring lengths from 150 to 1000 mm. Rulers are made with one or two scales (along both longitudinal edges). The measurement error with a ruler is summed up from the error in applying the scale, the parallax error, the error in aligning the zero mark of the scale with the edge of the part being measured, and the counting error.

The measurement error, depending on the length, is in the range of 0.2 - 0.5 mm, provided there is a sharp edge on the part and careful measurement. More often the measurement error reaches 1 mm.

Working gauges are used for direct measurements of precision products, for setting other working measuring instruments to zero or to size for relative measurements, for checking the accuracy and calibration of other measuring instruments, for particularly precise marking work, setting up machines, etc. End measures include end plane-parallel length measures and angular measures.

End plane-parallel length measures (Fig. 4) are made in the form of tiles, bars and cylinders (with end measuring planes). They are made of steel and hard alloy, which have 10 to 40 times greater wear resistance than steel. The measure is marked with its nominal size. For tile measures of more than 5.5 mm, the nominal size without indicating the units of measurement is marked on the non-working side surface, and for measures of 5.5 mm or less, they are marked on one of the working (measuring) planes.

Fig.4 End plane-parallel length measures

The size of the measure is taken to be its median length, which is determined by the length of the perpendicular dropped from the middle of one of the working planes to the opposite one. The length at a given point is determined by the length of the perpendicular drawn from this point by one work plane to the opposite. The largest difference between the median length and the length of the measure at any other point is taken as the deviation from plane-parallelism of the measure. Moreover, the zone on working planes 0.5 mm wide from the edges is not taken into account.

End gauges are assembled into sets that provide the possibility of obtaining blocks (connections) different sizes. Various sets consist of different quantities measures For example, they make sets of 42, 87, 112 measures, etc. in one box. In the main sets, one measure has a nominal size of 1.005 mm, some measures have nominal dimensions of 0.01 mm, some of 0.1 mm, one measure of 0.5 mm, some of the measures of 0.5 mm and some of 10 mm. The so-called micron set, consisting of 9 measures, includes measures with nominal sizes of 1.001; 1.002; etc. up to 1.009 mm or with dimensions 0.991; 0.992, etc. up to 0.999 mm. Using the main and micron kits you can assemble a large number of blocks of different sizes with an interval of 0.001 mm.

A large set allows you to obtain dimensions with fewer measures in a block than a small one, which ensures greater block accuracy (than less quantity measures in a block, the smaller the accumulated error from the number of measures). Each set additionally includes two pairs of protective measures. Protective measures, unlike the main ones, have a cut corner. Protective measures are used to install at the ends of the block in order to protect the main measures from excessive wear and damage.

The accuracy of each measure is determined by the accuracy of its production and the accuracy of verification (calibration). Working gauge blocks are divided into accuracy classes and are the most accurate working SI.

When assembling measures into a block, the effect of their grinding by working planes is used. Grinding is the fact that when one measure is applied and pushed onto another with little effort, they adhere to each other. The adhesive force of the new measures is so great that in order to separate them in the direction perpendicular to the lapped planes, a fairly large force is required (up to 300 - 800 N). The phenomenon of grinding has not yet been fully studied. Some believe that it is explained by the action of intermolecular cohesion forces, others - due to microvacuum. Most likely, both occur. The working planes of the measures are made with very small deviations in shape and very low roughness, and therefore the molecules of one measure are at such a close distance from the molecules of another measure that the action of intermolecular cohesion forces is manifested. Adhesion is significantly enhanced in the presence the thinnest film grease (0.1 - 0.02 microns), which remains on the surfaces of the measure after it is removed with a dry cloth and even after regular washing in gasoline. The force of intermolecular adhesion in the presence of a lubricating film can be explained in two ways. Firstly, by the fact that the depressions of the roughness irregularities are filled with lubricant and the lubricant molecules adhere to the molecules of the measures, increasing the total number of interacting molecules. Complete removal of lubricant leads to a significant reduction in the adhesive strength of the measures. The second explanation for the grindability of measures is that when the working planes of one measure are pressed against another, due to squeezing out lubricant from pores, cracks, cavities, roughness irregularities from the planes to the edges of the measures, microvacuuming of the cavities occurs inside the space between the measures, while simultaneously filling them with liquid lubricant perimeter of the edges, which isolates the space between the measures from environment, increasing the vacuum. This is proven by the fact that carbide measures adhere more strongly, because carbide is more porous than steel.

When selecting end measures for a block, you need to strive to ensure that the block consists of the smallest possible number of measures that are in a given set (in this case, the accumulated error from the number of measures in the block will be smaller and fewer measures will wear out).

The procedure for selecting measures is to sequentially select the fractional part of the required size, starting with last digit. Having selected the first measure, its size is subtracted from the given one and following the same rule, the size is determined next measure. For example, you need to select a block with nominal size 45.425 mm with a set of measures of 87 pieces:

1st measure 1.005 mm

2nd measure 1.42 mm

3rd measure 3 mm

4th measure 40 mm

Amount: 45.425 mm.

Tolerances for the production of measures are grouped by accuracy classes: 00, 0, 1, 2, 3 – for standard measures, 4, 5 – for working measures. Measures up to accuracy class 4 are divided into categories depending on the accuracy of verification. As a rule, it is not recommended to collect reference measures verified for high levels in blocks, because on each intermediate layer between measures, 0.05 - 0.10 microns are added, which can exceed the verification error itself. In order to eliminate errors in the verification of each measure, it is necessary to verify the already assembled block.

To increase the possibilities of using end blocks, special sets of accessories (devices) for them are produced (Fig. 5).

The kit box may contain holders (clamps) or ties (for measures over 100 mm with two holes), a base, for various purposes side panels and other accessories.

By analogy with end plane-parallel length measures, angular prismatic measures are used, which are also included in sets and can be used with accessories (Fig. 6, 7). They are produced in five types:

With one working angle with a cut off top (Fig. 6a);

With one working angle, acute-angled triangular (Fig. 6b);

With four working angles (Fig. 6c);

Hexagonal with uneven angular pitch (Fig. 6d);

Polyhedral with uniform angular pitch (8 and 12 faces) (Fig. 6e and 6f).

Checking angles using angle measures is usually carried out against the light. The error in measuring angles depends on the length and straightness of the sides of the angle being checked, the illumination of the workspace, the accuracy class of the measures and the qualifications of the worker. At the most favorable conditions measurement error, excluding the error of the measure itself, does not exceed 15 arc seconds.

A. Clamp

Rice. 5 End gauges and various holders for them (clamps - a.)

Rice. 6a Fig. 6b

Rice. 6c Fig. 6g

Rice. 6d Fig. 6e

Rice. 6 Prismatic measures for angle control

Vernier devices

Vernier instruments (vernier tools) are the most common measuring instruments. Their undeniable advantages: availability, ease of use and fairly high accuracy. They represent a large group of measuring instruments used for measuring linear dimensions and markings. Distinctive feature They are the presence of a rod on which the main scale is marked with marks every 1 mm, and a vernier with an additional scale for counting division fractions of the main scale. The main instruments are: calipers, caliper depth gauges, caliper gauges, caliper gauges. Vernier calipers are produced in three types: ShTs-1 with double-sided arrangement of jaws for external and internal measurements with a depth gauge; ShchTs-2 with a double-sided arrangement of jaws for external and internal measurements and for marking (without a depth gauge), ShTs-3 with a double-sided arrangement of jaws for external and internal measurements (without a depth gauge and jaws for marking). Most Applications find calipers of types ШЦ – 1, ШЦ – 2 (Fig. 7, 8). The smallest caliper is designed to measure sizes 0 - 125 mm, the largest 0 - 2000 mm (Previously they were produced for sizes 0 - 4000 mm). Vernier calipers have vernier scale divisions of 0.1 and 0.05 mm.

Rice. 7 Vernier caliper type ШЦ – 1

Modern electronic calipers of all types allow you to measure the dimensions of parts in the metric or inch measurement system. The caliper readings can be adjusted to “Zero” at any point on the scale, which allows you to control deviations of dimensions from the specified value. Most often, such calipers are equipped with a connector for outputting data to Personal Computer, printer or other device. They can also be equipped with a drive wheel, making it easier to operate with one hand.

Rice. 8 Vernier calipers type ШЦ – 12

1 – rod, 2 – frame, 3 – clamping element, 4 – vernier, 5 – working surface rods, 6 – rod scale, 7 – jaws with flat measuring surfaces for measuring external dimensions, 8 – jaws with edge measuring surfaces for measuring internal dimensions.

Rice. 8a Basic techniques for working with calipers

a, b – measurement of external dimensions, c – measurement of internal dimensions

Before starting to work with a caliper, it is recommended to check the zero setting by aligning the measuring jaws. Checking the zero (initial setting) of calipers and taking measurements must be carried out with the same force. It is recommended to place the part being measured as close as possible to the rod to reduce measurement error (Fig. 8a). Calipers are verified according to GOST 8.113-85 “GSI. Calipers. Verification methodology."

The vernier depth gauge is used to measure the depths of holes, grooves, grooves, heights of ledges, distances between parallel surfaces, which cannot be measured with a caliper without a depth gauge (Fig. 9a). Vernier depth gauges are produced for measuring sizes up to 400 mm (previously they were produced for sizes up to 500 mm). The vernier scale division value is 0.1 – 0.05 mm.

The height gauge is used for measuring heights and for marking (Fig. 9b). Gauge gauges are produced for measuring sizes up to 2500 mm with vernier scale divisions of 0.1 and 0.05 mm.

The vernier gauge is used to measure the thickness of the teeth of gear wheels along a constant chord (Fig. 10). Vernier gauges are produced in two standard sizes: for measuring gears with a tooth module of 1 - 18 mm and 5 - 36 mm with a vernier division value of 0.02 mm.

Rice. 9a Depth gauge Fig. 9b Shtangenreysmas (marking)

1 – frame

2 – scale

3 – frame

4 – vernier scale

Rice. 10 Vernier gauge

Micrometric instruments

Micrometers are one of the most popular types of measuring instruments and are used for precise measurements product sizes. The main micrometric instruments are micrometers different types(regular smooth, sheet, pipe, gear, threaded, tabletop) micrometric bore gauges, micrometric depth gauges.

These devices are based on the use of a screw pair that converts the rotational movement of a micrometer screw

(performed with micrometric precision) into the translational movement of one of the measuring rods. All micrometer instruments have a vernier scale division of 0.01 mm.

Conventional smooth micrometers are used for external measurements (Fig. 11). They are produced with measurement limits from 0 – 25 mm to 500 – 600 mm. Setting the micrometer to zero to measure the dimensions of St. 25 mm is performed using a special installation measure. Micrometers have a device for providing constant measuring force (“ratchet”). The measurement error with a micrometer arises due to errors: the manufacture of the micrometer itself, the setting standard (when measuring dimensions greater than 25 mm), the bending of the bracket under the influence of the measuring force, the reading of readings, temperature and contact deformations.

Rice. 11 Micrometer

1 – body (bracket); 2 – heel; 3 – micrometric screw; 4 – locking screw;

5 – stem; 6 – guide bushing; 7 – drum; 8 – adjusting nut;

9 – cap; 10 – ratchet.

Rice. 11a-c Examples of readings on a micrometer and depth gauge scale

Sheet micrometers are used to measure the thickness of sheet and broadband materials (Fig. 12). To allow material to be measured away from edges, the sheet micrometer has an extended arm.

Pipe micrometers are used to measure pipe wall thickness. This micrometer has a spherical heel and a bracket cut to make it possible to measure the wall thickness of pipes with internal diameter from 12 mm.

Gear micrometers (normal gauges) are used to measure the length of the common normal of the teeth of gear wheels (Fig. 13). They have a measuring sponge and a disc-shaped heel. A micrometer with disc measuring surfaces is used to measure soft materials, because it exerts the lowest specific pressure on the measured surfaces at the same measuring force. The diameter of the measuring surfaces is 60 mm.

Thread micrometers with inserts are used to measure the average diameter of external threads (Fig. 14).

Fig.12 Sheet micrometer

Figure 13. Gear micrometer

Rice. 14 Measuring circuit gear wheel dental micrometer

To measure internal dimensions from 50 to 6000 mm, micrometric bore gauges are used with a vernier scale division of 0.01 mm (Fig. 15). Operating these devices requires considerable skill. They are inconvenient for measuring deep holes. Both individual bore gauges with a range of movements of the micrometric measuring head of 25 mm are produced, as well as prefabricated bore gauges with precision extensions that increase the measurement range of the bore gauge and do not require additional adjustment after assembly with the micrometer head. Bore gauges can be adjusted to the measured size using mounting brackets, rings, micrometers, blocks of gauge blocks, length gauges, etc., which allows increasing the accuracy of measurements. It is recommended to measure deep holes in at least three sections perpendicular to the hole axis, in two mutually perpendicular directions in each section.

Rice. 15 Elements of a micrometric bore gauge - micrometric head:

1 – bushing; 2 – measuring tip; 3 – stem; 4 – stopper; 5 – bushing;

6 – drum; 7 – adjusting nut; 8 - micrometric screw; 9 – nut.

To measure the depths of grooves, blind holes and heights of ledges, I use micrometric depth gauges (Fig. 16). Replaceable precision rods 14 have flat or spherical measuring surfaces, so the depth gauges do not require additional adjustment after changing the measuring rods.

Fig. 16 Micrometric depth gauge

1 – traverse; 2 – stem; 3 – drum; 4 – micrometric screw; 5 – bushing;

6 – adjusting nut; 7 – cap; 8 – spring; 9 – ratchet tooth; 10 – ratchet;

11 – ratchet fastening screw; 12 – locking screw; 13 – installation measure (sleeve);

14 – measuring rods.

Lever devices

The main lever instruments are the lever micrometer (Fig. 17) and the lever bracket (Fig. 18). A lever micrometer, unlike a conventional smooth micrometer, in addition to the main scale and vernier scale, has a pointer reading device with a division value of 0.001 or 0.002 mm and does not have a device to ensure constant measuring force (the force closure is created by the force of the pointer readout head mechanism). Measurement limits on the dial reading head scale are ±0.02 mm or ±0.03 mm.

Lever clamps, unlike lever micrometers, do not have a micrometer head. They are intended only for relative measurements, i.e. Before measurement, the bracket is set to the size according to the block of gauge blocks. The division value of the reading pointer is 0.002 mm, the measurement limits on the scale are ± 0.08 or ± 0.14 mm.

Fig. 18 Lever micrometer

Indicating devices

Many measuring instruments are equipped measuring devices in the form of dial indicator heads (with gear transmission). The word "indicator" Latin origin. Translated into Russian it means a pointer, a determinant. The indicator head is a pointer device (Fig. 19). The scale division value is 0.01 mm, the measurement limits on the scale are 0 – 5 or 0 – 10 mm.

Such indicators are equipped, for example, with center gauges (biene gauges), bore gauges, brackets (Fig. 20), various racks(Fig. 21).

Fig.19 Indicator head

Rice. 20 Indicator bracket

Rice. 21 Stoikii

1 - base, 2 - object table for installing the product; 3-column; 4 - bracket;

5 - screw for fastening the measuring head; 6 - flywheel for moving the bracket (rack), 7 - bracket clamp screw; 8 - nut; 9 - rod; 10 - clamp;

11 - clamping screw; 12 - holder; 13 - holder fastening screw; 14 - spring ring; 15 - microfeed screw for precise installation of the measuring head to the size

Measuring machines

In measuring laboratories, measuring machines are used for accurate measurements of large lengths using absolute or comparative methods (Fig. 22). I produce domestic measuring machines with a measurement range of 1, 2 and 4 m ( inner dimensions 200 mm less). The division value of the most accurate scale of the optimometer installed on the machine is 0.001 mm.

Rice. 22 Testing and measuring machines

1 – base, 2 – headstock, 3 – racks, 4 – measuring table,

AND CONES

Concepts about normal angles and tapers

and tolerances on angular dimensions

Angle units. A common unit of measurement for angle is degree, which is equal to one three hundred and sixtieth part ( 1/360 ) circle. The degree is denoted by the sign ° and is divided by 60 minutes, and the minute is on 60 seconds. The minute and second are indicated by " and " respectively (for example, 60" indicates 60 seconds). Standards for angular measurements Multifaceted prisms are used, against which standard measures in the form of different polyhedra (with 6, 8 and 12 faces) are checked, the angles of which are made with high accuracy.

The International System of Units (SI) provides the radian as an additional unit of measurement for angles. Under radian refers to the angle between two radii of a circle, the length of the arc between which is equal to the radius. One degree is equal to , and one radian is equal to 57°17"44.8".

Normal angles(ST SEV 513-76). Angular dimensions, expressed in degrees, minutes and seconds, are very common in detail drawings. In order to reduce the number of different nominal values ​​of angles on parts, the standard provides for the use of three rows of nominal angle values, called "normal angles". The first row includes angles: 0°; 5°; 15°; 30°; 45°; 60°; 90°; 120°. It is recommended to take the value of these angles first.

The second row of angles, which is preferable to the 3rd row, contains all the angles of the 1st row and additionally the following: 30"; 1°; 2°; 3°; 4°; 6°; 7°; 8°; 10 °; 20°; 40° and 75°.

The third row includes the corners of the first and second row and additionally the following: ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; And .

Normal taper(GOST 8593-81) 2 rows: 1st row – 1:50; 1:20; 1:10; 1:5; 1:3; ; ; ; ; ; 2nd row – 1:30; 1:15; 1:12; 1:8; 1:7; .

Tolerances on angular dimensions. In ST SEV 178 – 75 angle tolerances provided in angular and linear quantities in 17 degrees of precision, designated AT1, AT2, AT3, etc. to AT17 in order of decreasing accuracy. Accuracy degrees AT1 to AT5 are intended for angles of gauges, measuring instruments and particularly precise products, and degrees AT6 to AT12 are for mating angles. The tolerance values, designated AT, are established both in degrees AT (seconds, minutes, degrees) and in microradians AT (μrad).

For the corners of prismatic elements of parts, tolerances are assigned depending on the nominal length of the shorter side of the angle, and for the corners of cones - depending on the nominal length of the cone. Within one degree of accuracy angular tolerances decrease with increasing length. This is explained by the fact that the greater the length of the base surface, the more accurate the installation of the part on the machine, and consequently, the smaller the processing error will be. To the corners prismatic parts AT angle tolerance, maybe assigned with a plus sign (+AT) or minus (-AT), or symmetrically (AT).