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section Fourth

Tolerances and landings.
Measuring tool

Chapter IX.

Tolerances and landings

1. The concept of interchangeability of parts

At modern plants, machines, cars, tractors and other machines are not made by units and not even dozens and hundreds, but thousands. With such production sizes, it is very important that each detail of the machine when assembling exactly approached its place without any additional fitter fit. It is equally important that any detail entering the assembly allowed the replacement of its other one with it the destination without any damage to the work of the entire finished machine. Details that satisfy such conditions are called interchangeable.

Interchangeability of details - This property of details occupy its places in nodes and products without any preliminary selection or fit on the place and perform their functions in accordance with the prescribed specifications.

2. Conjugation of details

Two details, moving or motionlessly connected to each other, called matchy. The size of which the connection of these parts is called, called mattered size. Dimensions for which the details do not occur are called free sizes. An example of a conjugated sizes can be the diameter of the shaft and the corresponding diameter of the hole in the pulley; An example of free sizes is the outer diameter of the pulley.

To obtain interchangeability, the conjugated dimensions of the parts must be accurately executed. However, such treatment is complex and not always appropriate. Therefore, the technique has found a way to receive interchangeable parts when working with approximate accuracy. This method is that for different working conditions, the parts are set by the permissible deviations of its size, at which there is still impeccable work of the part in the machine. These deviations calculated for various working conditions of the part are built in a specific system called system tolerances.

3. Concept for tolerances

Size characteristics. The calculated part of the part is affixed in the drawing, from which deviations are counted, called nominal size. Typically, nominal dimensions are expressed in high-length.

The size of the part actually received during processing is called valid size.

The dimensions between which the actual part size can fluctuate, are called limit. Of them, the larger size is called the greatest limit size, and smaller - the lowest limit size.

Deviation Called the difference between the limit and nominal size of the part. The deviation drawing is usually indicated by numerical values \u200b\u200bat a nominal amount, and the upper deviation is indicated above, and the lower is lower.

For example, in the amount of the nominal size 30, and the deviations will be +0.15 and -0.1.

The difference between the largest limit and nominal sizes is called upper deviation, and the difference between the lowest limit and nominal sizes - lower deviation. For example, the size of the shaft is equal. In this case, the greatest limit will be:

30 +0.15 \u003d 30.15 mm;

upper deviation will be

30.15 - 30.0 \u003d 0.15 mm;

the smallest margin will be:

30 + 0.1 \u003d 30.1 mm;

lower deviation will be

30.1 - 30.0 \u003d 0.1 mm.

Tolerance for manufacture. The difference between the greatest and the lowest limits is called tolerance. For example, for the size of the shaft, the tolerance will be equal to the difference difference, i.e.
30.15 - 29.9 \u003d 0.25 mm.

4. Gaps and tension

If the part with the hole is to put on the shaft with a diameter, i.e. with a diameter under all conditions less than the diameter of the hole, then the conduction of the shaft with the hole will necessarily be a gap, as shown in Fig. 70. In this case, landing is called mobileSince the shaft can rotate freely in the hole. If the shaft size is e. e. Always more than the size of the hole (Fig. 71), then when the shaft is connected, it will be necessary to pinch into the hole and then in the connection it turns out tension.

Based on the above, you can make the following conclusion:
the gap is called the difference between the valid sizes of the hole and the shaft, when the hole is greater than the shaft;
tension is called the difference between the valid shaft sizes and the holes when the shaft is greater than the hole.

5. Landings and accuracy classes

Landing. Landing is divided into movable and fixed. Below are the most applied landings, and their abbreviations are given in brackets.

Accuracy classes. From practice it is known that, for example, details of agricultural and road vehicles without harm to their work can be made less precisely than the parts of the lathes, cars, measuring instruments. In this regard, in mechanical engineering, details of different machines are manufactured by ten different grades of accuracy. Five of them more accurate: 1st, 2nd, 2a, 3rd, for; Two less accurate: 4th and 5th; Three others - rude: 7th, 8th and 9th.

To know, in what class of accuracy you need to make the item, in the drawings next to the letter, indicating the landing, the figure specifies the accuracy class. For example, with 4 means: sliding landing of the 4th grade accuracy; X 3 - running 3rd grade accuracy; P is a dense landing of the 2nd grade accuracy. For all landings of the 2nd class, the number 2 is not put, since this accuracy class is applied particularly wide.

6. Hole system and shaft system

There are two tolerance location systems - hole system and shaft system.

The opening system (Fig. 72) is characterized by the fact that in it for all landings of the same degree of accuracy (one class), assigned to the same nominal diameter, the hole has constant limit deviations, the diversity of landings is obtained by changing the limit Shaft deviations.

The shaft system (Fig. 73) is characterized by the fact that in it for all landings of the same degree of accuracy (one class), assigned to the same nominal diameter, shaft has constant limit deviations, the diversity of landings in this system is carried out for Account of change of limit deviations of the hole.

In the drawings, the hole system is denoted by the letter A, and the shaft system is the letter V. If the hole is made via the hole system, then the nominal size is given a letter A with a digit corresponding to the accuracy class. For example, 30A 3 means that the hole must be processed by the opening system of the 3rd class accuracy, and 30a by the opening system of the 2nd accuracy class. If the hole is processed through the shaft system, then the nominal size is set to landing and the corresponding accuracy class. For example, a hole 30C 4 means that the hole must be processed with the limit deviations by the shaft system, along the sliding landing of the 4th grade of accuracy. In the case when the shaft is manufactured by the shaft system, put the letter B and the corresponding accuracy class. For example, 30B 3 will mean the treasure of the shaft according to the string class of the 3rd of accuracy, and 30B - according to the 2nd class of the accuracy class.

In mechanical engineering, the hole system is used more often than the shaft system, as it is associated with smaller expenditures on the tool and snap. For example, to process the hole of this nominal diameter with the hole system for all landings of the same class, only one scan is required and for measuring the hole - one / limit plug, and with a shaft system for each planting within the same class, a separate sweep is needed and a separate limit plug.

7. Table deviations

To determine and destin the classes of accuracy, landings and the magnitude of tolerances, use special reference tables. Since permissible deviations are usually very small values, so as not to write extra zeros, in the tables of tolerances they are denoted by thousands of millimeters called microns; One micron is 0.001 mm.

As an example, a table of the 2nd accuracy class for the hole system is given (Table 7).

In the first column of the table, the nominal diameters are given, in the second column - deviations of the hole in the microns. In the remaining graphs, various landings are given with the corresponding deviations. The plus sign indicates that the deviation is added to the nominal size, and minus - that the deviation is deducted from the nominal size.

As an example, we define the landing of the movement in the opening system of the 2nd accuracy class for connecting the shaft with a hole of the nominal diameter of 70 mm.

The nominal diameter 70 lies between the dimensions of 50-80 placed in the first column of the table. 7. In the second column we will find the corresponding deviations of the hole. Consequently, the largest limiting size of the opening will be 70.030 mm, and the smallest of 70 mm, since the lower deviation is zero.

In the column "Landing of motion" against size from 50 to 80, the deviation for the shaft is therefore, the largest limit size of the shaft 70-0,012 \u003d 69.988 mm, and the smallest limit size is 70-0.032 \u003d 69.968 mm.

Table 7.

Limit deviations of the hole and shaft for the opening system for the 2nd accuracy class
(on OST 1012). Dimensions in microns (1 mk \u003d 0.001 mm)

Control questions 1. What is called interchangeability of parts in mechanical engineering?
2. What are the permissible deviations of the size of the parts appoint?
3. What is nominal, limit and valid sizes?
4. Can the limit value equal to the nominal?
5. What is called tolerance and how to determine the tolerance?
6. What is called upper and lower disabilities?
7. What is called a gap and tension? Why are it planned in the connection of two details a gap and tension?
8. What are the landing and how are they denoted in the drawings?
9. List the accuracy classes.
10. How much landing has the 2nd grade of accuracy?
11. What is the difference between the hole system from the shaft system?
12. Will there be limit deviations of the hole for various landings in the hole system?
13. Will there be limit deviations of the shaft for various landings in the opening system?
14. Why in mechanical engineering The hole system is used more often than the shaft system?
15. How are the conditional designations of deviations in the sizes of the hole are affixed in the drawings, if the parts are performed in the hole system?
16. Which units are deviations in tables?
17. Determine using Table. 7, deviations and admission to the manufacture of the shaft with a nominal diameter of 50 mm; 75 mm; 90 mm.

Chapter X.

Measuring tool

To measure and verify the size of the parts of the turner, you have to use various measuring instruments. For not very accurate measurements, measuring rules, crowns and gutomers are used, and for more accurate - calibrations, micrometers, calibers, etc.

1. Measuring line. Calipers. Nutromer

Yardstick (Fig. 74) serves to measure the length of parts and ledges on them. The most common steel rules with a length of 150 to 300 mm with millimeter divisions.

The length is measured, directly applying a ruler to the detail processed. The start of divisions or zero bar is combined with one of the ends of the measured part and then count the touch, which accounts for the second end of the part.

Possible measurement accuracy with a ruler 0.25-0.5 mm.

Kronzirkul (Fig. 75, a) is the simplest tool for coarse measurements of the external dimensions of the processed parts. The kronzirkul consists of two curved legs, which are sitting on one axis and can rotate around it. Removal of the protrusion legs are somewhat longer than the measured size, a slight tapping about the measured part or some solid object shifted them so that they come to the outdoor surfaces of the measured part. The method of sizes with the measured part to the measuring line is shown in Fig. 76.

In fig. 75, 6 shows the spring kronzirkul. It is mounted on the size with a screw and nut with fine threads.

The spring kronchirkul is somewhat more convenient, since it saves the set size.

Nutrometer. For coarse measurements of internal dimensions, the nutrometer is shown in Fig. 77, a, as well as a spring norter (Fig. 77, b). The nutromer device similar to the Kroncirkul device; It is also similar to the measurement by these tools. Instead of the nutrometer, you can use the crown, the crying of its legs is one for another, as shown in Fig. 77, in.

The accuracy of the measurement by the Kronzirkul and the chuteomer can be added to 0.25 mm.

2. Calcirculation with an accuracy of reference 0.1 mm

The accuracy of measuring the measuring ruler, the croncyrcule, the chuteomer, as already indicated, does not exceed 0.25 mm. A more accurate tool is the caliper (Fig. 78), which can be measured both the outer and the internal dimensions of the processed parts. When working on a turning machine, the caliper is also used to measure the depth of the shading or the ledge.

The caller consists of a steel rod (ruler) 5 with divisions and sponges 1, 2, 3 and 8. Sponges 1 and 2 are one whole with a ruler, and sponges 8 and 3 are one as a frame 7, sliding according to the ruler. Using the screw 4, you can fix the frame on the line in any position.

To measure the outer surfaces, sponges 1 and 8 are served to measure the inner sponge surfaces 2 and 3, and for measuring the depth of the plot - exchanger 6 associated with the frame 7.

On the frame 7 there is a scale with strokes for reference fractional fraction of a millimeter, called nonius. Nonius allows measurements with an accuracy of 0.1 mm (decimal nonius), and in more accurate calipers - with an accuracy of 0.05 and 0.02 mm.

Nonius device. Consider how the ignius is counting on the nonius in the caliper with an accuracy of 0.1 mm. The nonius scale (Fig. 79) is divided into ten equal parts and takes length equal to nine divisions of the scale scale, or 9 mm. Therefore, one nonius division is 0.9 mm, i.e. it is shorter than each division of the line of 0.1 mm.

If you closely sponges of the caliper, the zero barcode of the Nonius will accurately coincide with the zero stroke of the line. The rest of the strokes of the Nonius, besides the latter, there will be no such coincidence: the first barcode of the Nonius will not reach the first stroke of the line of 0.1 mm; The second barcode of the nonius will not reach the second stroke of the line 0.2 mm; The third barcode of the Nonius does not reach the third stroke of the line of 0.3 mm, etc. The tenth of the barcode of Nonius will accurately coincide with the ninth string of the line.

If you move the frame in such a way that the first bar of the nonius (not counting zero) coincided with the first stroke of the line, then there is a gap between the sponges of the calipers, equal to 0.1 mm. With the coincidence of the second stroke of the Nonius with the second stroke of the line, the gap between sponges is already 0.2 mm, with the coincidence of the third stroke of the Nonius with the third stroke of the line, the gap will be 0.3 mm, etc. Consequently, that barcode of Nonius, which exactly coincides with what -Lo stroke line, shows the number of tenths of a millimeter.

When measuring the caliper, the whole number of millimeters, which is judged by the position occupied by the zero stroke of the nonius, and then look at what the stroke of Nonius coincided with the barcode of the measuring line, and determine the tenths of the millimeter.

In fig. 79, it is shown the position of the nonius when measuring the part with a diameter of 6.5 mm. Indeed, the zero barcode of the nonius is between the sixth and seventh strokes of the measuring line, and, consequently, the detail diameter is 6 mm plus the testimony of the nonius. Next, we see that the fifth barcode of the nonius coincided with one of the rods of the line, which corresponds to 0.5 mm, so the diameter of the part will be 6 + 0.5 \u003d 6.5 mm.

3. Chatchenglouder

To measure the depth of the shackles and grooves, as well as to determine the correct position of the ledges along the roller length, serves a special tool called schanganGluubigener (Fig. 80). The device of the calibration is similar to the caliper device. The line 1 is freely moving in the frame 2 and is fixed in it in the desired position using the screw 4. The line 1 has a millimeter scale at which with the help of nonioce 3 available on the frame 2, the depth of the shading or groove is determined, as shown in Fig. 80. The countdown on Nonius is conducted in the same way as when measuring the caliper.

4. Precision caller

For work performed with greater accuracy than still considered, apply precision (i.e. accurate) calipers.

In fig. 81 depicts the precision scholarser of the plant. Vekova having a measuring line of 300 mm long and nonius.

The length of the nonius scale (Fig. 82, a) is 49 divisions of the measuring line, which is 49 mm. These 49 mm are definitely separated by 50 parts, each of which is 0.98 mm. Since one division of the measuring line is 1 mm, and one division of the nonius is equal to 0.98 mm, it can be said that each division of the nonius is shorter than each division of the measuring line by 1.00-0.98 \u003d 0.02 mm. This value of 0.02 mm denotes that accuracywhich the nonius of the considered precision caller When measuring parts.

When measuring the precision calipers to the amount of entire millimeters, which is passed with a zero stroke of the nonius, must be added as many hundredths of the millimeter, as long as the barcode of the Nonius, which coincided with the gear of the measuring line. For example (see Fig. 82, b), in the line of the caliper of the zero bar of Nonius passed 12 mm, and its 12th bar coincided with one of the strokes of the measuring line. Since the coincidence of the 12th stroke of the nonius means 0.02 x 12 \u003d 0.24 mm, then the measured size is 12.0 + 0.24 \u003d 12.24 mm.

In fig. 83 shows the precision caliber plant scholarser with an accuracy of 0.05 mm.

The length of the nonus scale of this caliper, equal to 39 mm, is divided into 20 equal parts, each of which is accepted for five. Therefore, against the fifth stroke of the nonius, there is a figure 25, against the tenth - 50, etc. The length of each of the division of Nonius is equal to

From fig. 83 It can be seen that with close sponges of the caliper closed, only zero and the last stroke of the nonius coincide with the line strokes; The remaining strokes of the nonius of such a coincidence will not have.

If you move the frame 3 to the coincidence of the first stroke of the nonius with the second stroke of the line, then the gap is 0-1.95 \u003d 0.05 mm between the measuring surfaces of the sinks of the calipers. With the coincidence of the second stroke of the nonius with the fourth stroke of the line, the gap between the measuring surfaces of the sponges will be 4-2 x 1.95 \u003d 4 - 3.9 \u003d 0.1 mm. With the coincidence of the third stroke of the Nonius with the next stroke, the gap will be 0.15 mm.

The countdown on this caliper is carried out similarly outlined above.

The precision calibration (Fig. 81 and 83) consists of a ruler 1 with sponges 6 and 7. On the line of divisions are applied. According to the ruler 1, a frame 3 can move with sponges 5 and 8. Nonius was screwed to the frame. 4. For coarse measurements, the frame 3 is moved according to the line 1 and after fixing with screw 9 produce countdown. For accurate measurements, the micrometric feed frame 3, consisting of screw and nut 2 and clamping 10, enjoy the screw 10, the rotation of the nut 2 is supplied with a micrometer screw frame 3 to a dense contact of the sponge 8 or 5 with the measured part, after which they produce a countdown.

5. Micrometer

The micrometer (Fig. 84) is used to accurately measure the diameter, length and thickness of the part being processed and gives the counting accuracy of 0.01 mm. The measured part is located between the fixed heel 2 and the micrometric screw (spindle) 3. The rotation of the drum 6 spindle is removed or approaches the heel.

In order for the drum to rotate, too strongly pressing the spindle on the measured part, there is a safety head 7 with a ratchet. Rotating head 7, we will push the spindle 3 and press the item to the heel 2. When this press is sufficient, with further rotation of the head, its ratchet will slip and the ratchet sound will be heard. After that, the head rotation is stopped, secured with the rotation of the clamping ring (stopper) 4 the resulting disclosure of the micrometer and produce a countdown.

For the production of stems on the stem 5, which constitutes one integer with the bracket 1 of the micrometer, the scale with millimeter divisions, separated by half, is applied. The drum 6 has a beveled face, separated around the circle to 50 equal parts. Strokes from 0 to 50 every five divisions are marked with numbers. With a zero position, i.e., when contacting the heel with a spindle, the zero touch on the bracket of the drum 6 coincides with the zero stroke on the stem 5.

The mechanism of the micrometer is designed in such a way that with the full turnover of the drum, the spindle 3 will move by 0.5 mm. Therefore, if you turn the drum is not full of turnover, i.e. not by 50 divisions, but on one division, or part of the turnover, then the spindle will move to This is the accuracy of the micrometer count. When counting, first look at how many millimeters or as many as a half millimeters opened the drum on the stem, then the number of hundredths of the millimeter is added to this, which coincided with the line on the stalk.

In fig. 84 on the right is shown the size shot by the micrometer when measuring the part; It is necessary to make a count. The drum opened 16 entire divisions (half not open) on the stem scale. With the line of the stem coincided with the seventh barge; Consequently, we will have another 0.07 mm. The full count is 16 + 0.07 \u003d 16.07 mm.

In fig. 85 shows several measurements by micrometer.

It should be remembered that the micrometer is an accurate instrument requiring a gentle relationship; Therefore, when the spindle touched the surface of the measured part, one should not rotate the drum, and for further movement of the spindle to rotate the head 7 (Fig. 84) until the scraping sound follows.

6. GUTROMERS

Nutromers (Schtihmas) are used for accurate measurements of the internal dimensions of parts. There are nutromers permanent and sliding.

Permanent, Nutrometer (Fig. 86) is a metal rod with measuring ends having a ball surface. The distance between them is equal to the diameter of the measured hole. To exclude the influence of the heat of the hand holding a nutrometer, on its actual size, the norter is supplied with a holding (handle).

To measure the internal dimensions with an accuracy of 0.01 mm, micrometric nutromers are used. The device is similar to the micrometer device for external measurements.

The head of the micrometric nutromer (Fig. 87) consists of a sleeve 3 and a drum 4 connected to a micrometric screw; Screw step 0.5 mm, move 13 mm. The sleeve places the stopper 2 and heel / with a measuring surface. Holding the sleeve and rotating the drum, you can change the distance between the measuring surfaces of the noutomer. The references produce as a micrometer.

The measurement limits of the headmas head - from 50 to 63 mm. For measuring large diameters (up to 1500 mm), the extension cords 5 are screwed on the head.

7. Limit measuring instruments

With a serial manufacture of parts for admission to the use of universal measuring instruments (caliper, micrometer, micrometric nutrometer) is impractical, since the measurement by these tools is a relatively complex and long-term operation. Their accuracy is often insufficient, and, moreover, the measurement result depends on the skill of the employee.

To check whether the dimensions of parts are located in exactly the limits, use a special tool - limit caliber. Caliburs for checking shafts are called brackets, and to check holes - plugs.

Measuring limit brackets. Bilateral limit brace (Fig. 88) has two pairs of measuring cheeks. The distance between the cheeks of one side is equal to the smallest limit, and the other is the largest limiting size of the part. If the measured shaft passes into the large side of the bracket, therefore, its size does not exceed the permissible, and if not, it means it is too large. If the shaft also passes in the smaller side of the bracket, it means that its diameter is too small, that is, less permissible. Such a shaft is a marriage.

The side of the bracket with a smaller size is called disproverable (brands "not"), the opposite side with a large size - passing (brand "pr"). The shaft is recognized as suitable if the bracket, lowered by the passage side, slides down under the influence of its weight (Fig. 88), and the non-voluntary side does not find on the shaft.

To measure the shafts of a large diameter instead of bilateral brackets, one-sided (Fig. 89) is used, in which both pairs of measuring surfaces lie one after another. The front measuring surfaces of such a bracket check the largest permissible detail diameter, and the rear is the smallest. These brackets have a smaller weight and significantly accelerate the control process, as it is enough to impose a bracket once.

In fig. 90 shows adjustable limit braceWhich, when wear, it is possible to restore the correct dimensions by rearranging the measuring pins. In addition, such a bracket can be adjusted for the specified sizes and thus a small set of brackets to check a large number of sizes.

To rearrange, it is necessary to weaken the lock screws 1 on the left leg, respectively, move the measuring pins 2 and 3 and fix the screws 1 again.

Have widespread flat limit brackets (Fig. 91), made from sheet steel.

Measuring limit plugs. Cylindrical limit caliber cork (Fig. 92) consists of a passing tube 1, non-passing tube 3 and handles 2. Passing plug ("Pr") has a diameter equal to the smallest permissible hole of the hole, and the non-passing plug ("not") is the greatest. If the plug "PR" passes, and the "not" tube does not pass, the diameter of the hole is greater than the smallest limit and less than the greatest, that is, lies in permissible limits. The passing tube has a big length than non-proven.

In fig. 93 shows the measurement of the opening of the limit plug on the lathe. The passage side should easily pass through the hole. If the disadvantage is included in the hole, then the item is branded.

Cylindrical cylinder corks for large diameters are inconvenient due to their high weight. In these cases, they use two flat cork calibers (Fig. 94), of which one has the size equal to the greatest, and the second is the smallest allowable. The passage side has a large width than peporate.

In fig. 95 shows adjustable limit plug. It can be adjusted for several sizes as well as the adjustable limit bracket, or restore the correct size of the worn measuring surfaces.

8. Reismasses and indicators

Rayish. To accurately verify the correct installation of the part in the four-digit chuck, on the square, etc. apply rayysmas.

With the help of a flight, the marking of the center holes in the ends of the part can also be made.

The simplest reismaas is shown in Fig. 96, a. It consists of a massive tile with precisely treated by the lower plane and the rod, which is moving the slider with a needle-fucking.

Rysmasas more advanced design is shown in Fig. 96, b. The needle of 3 flights with a hinge 1 and a clamp 4 can be connected with the top to the surface being checked. Accurate installation is carried out with screw 2.

Indicator. To control the accuracy of processing on metal cutting machines, checking the processed part on ovality, taper, the indicator is used to check the accuracy of the machine itself.

The indicator (Fig. 97) has a metal housing 6 in the form of a clock in which the mechanism of the device is concluded. Through the case of the indicator passes the rod 3 with the protruding the outward tip, which is always under the influence of the spring. If you press the rod from the bottom upward, it moves in the axial direction and at the same time it will rotate the arrow 5, which will move along the dial with a scale of 100 divisions, each of which corresponds to the movement of the rod by 1/100 mm. When moving the rod per 1 mm arrow 5 will make a full turn on the dial. For the countdown of entire revolutions, the arrow 4 is served.

When measuring, the indicator should always be rigidly fixed relative to the original measuring surface. In fig. 97, and depicted a universal rack for fastening the indicator. Indicator 6 using rods 2 and 1 couplings 7 and 8 are fixed on a vertical rod 9. The rod 9 is strengthened in the groove of the prism 12 with a nut 10 nut.

To measure the deviation of the part from the specified size, the indicator tip to contact with the measured surface and notice the initial reading of the arrows 5 and 4 (see Fig. 97, b) on the dial. Then move the indicator relative to the measured surface or the measured surface relative to the indicator.

The deviation of the arrow 5 from its initial position will show the magnitude of the bulge (depressions) in the hundredths of the millimeter, and the deviation of the arrow 4-in the time of millimeters.

In fig. 98 shows an example of using the indicator to check the coincidence of the centers of the front and backstarts of the lathe. For a more accurate check, the accurate polished roller should be installed between the centers, and the indicator is indicator. By summing up the indicator button to the roller surface to the right and noticing the indicator of the indicator arrow, move manually the caliper with the indicator along the roller. The difference in deviations of the arrow of the indicator in the extreme positions of the roller will show which magnitude the housing of the backstock should be moved in the transverse direction.

Using the indicator, you can also check the mechanical surface of the part processed on the machine. The indicator is fixed in the slit holder instead of the cutter and move along with the cut holder in the transverse direction so that the button of the indicator concerns the surface being checked. Deviation of the indicator arrows will show the magnitude of the beyon of the end plane.

Control questions 1. From what details is the caliper with an accuracy of 0.1 mm?
2. How does Nonius caliper designed with an accuracy of 0.1 mm?
3. Install the sizes on the calipers: 25.6 mm; 30.8 mm; 45.9 mm.
4. How many divisions is the nonius of the precision caliper with an accuracy of 0.05 mm? The same, with an accuracy of 0.02 mm? What is the length of one nonius division? How to read the testimony of Nonius?
5. Install the sizes in the precision caliper: 35.75 mm; 50.05 mm; 60.55 mm; 75 mm.
6. What parts is the micrometer?
7. What is the move of the micrometer's screw?
8. How to measure the measurement on the micrometer?
9. Set the micrometer dimensions: 15.45 mm; 30.5 mm; 50.55 mm.
10. In what cases is the chuters apply?
11. What are the limit calibers?
12. What is the purpose of the passage and non-passage of the limit calibers?
13. What are the designs of the limit brackets you know?
14. How to check the accuracy of the limit plug? Limit bracket?
15. What is the indicator? How to use it?
16. How is the raismas and what is used for?

Application in drawings tolerances and landings. The principle of interchangeability.

The tolerance field is called a field limited to the upper and lower disabilities. The tolerance field is determined by the value of admission and its position relative to the nominal size. With the graphic image, it concludes between the lines corresponding to the upper and lower deviations of the zero line.

When applied to drawings with upper and lower deflection, specific rules should be followed:

The upper or lower deviation equal to zero is not specified.

The number of signs in the upper and lower deviations are aligned, if necessary, to maintain a single number of characters to the right finish zeros, for example æ .

The upper and lower deviations are written in two lines, and the upper deviation is placed above the lower; The height of the deviation numbers is approximately twice as fewer nominal size numbers;

In the case of a symmetrical location of the admission field relative to the zero line, i.e. When the upper deviation is equal in the absolute value of the lower deflection, but the opposite by the sign, their value is indicated after the sign ± numbers equal to the height of the nominal size;

The tolerance field characterizes not only the value of the tolerance, but also the location of it relative to the nominal size or zero line. It can be located above, below, symmetrically, one-sided and asymmetrically relative to the zero line. For clarity in the drawings of parts over the dimensional line after the nominal size, it is customary to indicate the upper and lower deviation in millimeters with their signs, as well as for clarity, build the layout of the shaft tolerance field or holes relative to the zero line; At the same time, the upper and lower deviations are delayed in micrometers, and not in millimeters.

Landing- the nature of the connection of the part, determined by the magnitudes of the gaps of the gaps or testers. Distinguish landings of three teaks:

With gap

with tension

transitional.

Note that the shaft and the hole forming the landing have the same nominal size and differ in the upper and lower deviations. For this reason, in the drawings over the dimensional line, the landing is denoted after the nominal size of the fraction, in which the numerators of which record the limit deviations for the hole, and in the denominator - similar data for the shaft.

The difference between the sizes of the shaft and the holes to the assembly, if the size of the shaft is greater than the size of the opening, is called tension N.. Landing with tension – this landing at which the tension is provided in the connection is ensured, and the opening tolerance field is located under the shaft tolerance field.

Least N. mIN. And the greatest N. max Strengths have important landings with tension:

N. mIN. takes place in the connection if in the hole with the highest limit size D. max The shaft of the smallest limit will be pressed d. mIN. ;

N. max takes place with the smallest limit size of the hole D. mIN. and the greatest limit size of the shaft d. max .

The difference in the size of the opening and shaft to the assembly, if the size of the hole is greater than the shaft hole, is called gap S.. The landing at which the clearance is provided in the connection and the opening tolerance field is located above the shaft tolerance field, is called a gap planting. It is characterized by the smallest S. mIN. And the greatest S. max Gas:

S. mIN. takes place in the connection of the hole with the shaft is formed if in the hole with the lowest limit size D. mIN. will be installed shaft with the highest size d. max;

S. max takes place with the highest limit of the hole D. max and the smallest limit size of the shaft d. mIN. .

The difference between the greatest lowest gaps or the sum of the tolerances of the hole and the shaft component of the compound is called admission landing.

A landing at which it is possible to obtain, both gap and tension, are called transitional landing. In this case, the tolerance and shaft tolerance fields overlap partially or completely.

Due to the inevitable fluctuation of the sizes of the shaft and the holes from the largest to the smallest values, when assembling parts, the oscillation of gaps and testers occurs. The greatest and smallest gaps, as well as the tights are calculated by formulas. And the smaller the oscillation of gaps or testers, the higher the accuracy of the landing.

The principle of interchangeability I.

The design property of the component part of the product, providing the possibility of its use instead of another without additional processing, with the preservation of the specified quality of the product, which includes, is called interchangeability. With complete interchangeability of the same type, products, such as bolts, studs, can be made and installed on "their own" without additional processing or preliminary fit.

Along with complete interchangeability, it is allowed to assemble products by methods of incomplete and group interchangeability, regulation and fit.

Incomplete interchangeability include assembly of products based on theoretical and probability calculations.

With group interchangeability, parts made on widespread machinery with technologically made tolerances are sorted in size to several dimensional groups; Then check the detail assembly of the same group number.

The regulatory method involves an assembly with regulation of position or sizes of one or more individual, pre-selected product details called compensators.

The fit method is the assembly of products with a fit of one and collected parts. Interchangeability provides high quality products and reduces their cost, while promoting the development of progressive technology and measuring technology. Without interchangeability, modern production is impossible. Interchangeability is based on standardization- finding a solution for repeating problems in the sphere of science, technology and economics aimed at achieving an optimal order of streamlining in a certain area. Standardization is aimed at improving and managing the national economy, improving the technical level and product quality, etc. The main task of standardization is to create a system of regulatory and technical documentation, which establishes requirements for standardization objects, is required for use in certain areas of activity. The most important standardization regulatory document is the standard developed on the basis of achieving domestic and foreign science, technology, technologies of best practices and providing solutions that are optimal for the country's economic and social development.

Tolerances and landings are normalized by state standards included in two systems: ESDP - "Unified tolerance and landing system" and ONV - "main norms of interchangeability." ESDP applies to tolerances and landing the size of smooth items of details and landing formed when connecting these parts. ONV regulates tolerances and landing of keyproof, slotted, threaded and conical compounds, as well as gears and wheels.

Tolerances and landings indicate the drawings, sketches of technological maps and in other technological documentation. Based on tolerances and landings, technological processes of manufacturing parts and control of their size are developed, as well as assembling products.

On the working drawing, the parts affix the dimensions called nominal, the limit deviations of the size and the conditional designations of the tolerance fields. The nominal size of the opening is denoted by D., and the nominal size of the shaft - d.. In that cases when the shaft and the hole form a single connection for the nominal compound size, the total size of the shaft and the holes indicated by d (D).The nominal size is chosen from a number of normal linear dimensions according to GOST 6636-69. limiting the number of sizes used. For sizes in the interval 0.001-0.009 mma number set: 0.001; 0.002; 0.003; .. 0.009 mm. There are four main rows of normal sizes. (RA5; RA10; RA20; RA40)and one series of additional sizes. Preferred rows with a larger gradation of dimensions, i.e. row RA5they will prefer to be preferred RA10etc.

Process the part exactly for nominal size is almost impossible due to the numerous errors affecting the quality of processing. The dimensions of the processed part differ from the specified nominal size. Therefore, they are limited to two fiction dimensions, one of which (greater) is called the highest limit, and the other (smaller) is the lowest limit. The greatest limit of the holes are denoted D. max , Vala d. max ; Accordingly, the smallest limit of the hole D. mIN. , and Vala d. mIN. .

Measuring the hole or shaft with a permissible error determine their valid size. The item is suitable if its valid size is longer than the smallest size, but does not exceed the greatest limit.

In the drawings, instead of limit sizes near the nominal size, two limit deviations indicate, for example .

Deviationthe algebraic difference between sizes and the corresponding nominal size is called. Thus, the nominal size also serves as the beginning of the deflection reference and determines the position of the zero line.

Actual deviation- Algebraic difference between valid and nominal size.

Limit deviation- Algebraic difference between valid and nominal sizes. One of the two limit deviations is called the top, and the other - the bottom.

The upper and lower deviation can be positive, i.e. with a "plus" sign, negative, i.e. with a "minus" sign, and equal zero.

Zero line- The line corresponding to the nominal size from which the sizes deviations are deposited during the graphic image of tolerances and landings (GOST 25346-82). If the zero line is located horizontally, the positive deviation is deposited up from it, and negative is down.

System of tolerances and landings

ESDP standards are applied to smooth conjugated and non-distilled elements of parts with rated dimensions up to 10,000 mm (Table 1)

Table. 1 Standards ESDP

Qualitets

Classes (levels, degrees) of accuracy in ESDP are called qualitates, which distinguishes them from the accuracy classes in the OST system. Quality(degree of accuracy) - the gradation stage of the values \u200b\u200bof the tolerances of the system.

Tolerances in each qualite increase with an increase in the nominal sizes, but they correspond to the same level of accuracy determined by the qualificate (its sequence number).

For this nominal size, admission for different patterns of unequal, as each qualitude determines the need to apply certain methods and means of processing products.

In ESDP, 19 qualifications indicated by the sequence number: 01; 0; one; 2; 3; four; five; 6; 7; eight; nine; 10; eleven; 12; 13; fourteen; fifteen; 16 and 17. The highest accuracy corresponds to the qualification 01, and the lowest is the 17th qualitude. Accuracy decreases from qualitate 01 to qualithe 17.

The admission of qualitate conventionally designate the capital latin letters of the IT with the qualitate number, for example, IT6 is the tolerance of the 6th qualitate. In the future, under the word, the tolerance means the tolerance of the system. The qualifications 01, 0 and 1 are provided for estimating the accuracy of plane-parallel terminal lengths, and the qualifications 2, 3 and 4 are to evaluate smooth calibers and calibers-brackets. The dimensions of the details of high-precision responsible compounds, such as rolling bearings, necks of the crankshafts, parts connected to the rolling bearings of high precision classes, spindles of precision and accurate metal-cutting machines and others are performed on the 5th and 6th qualifications. Caltats 7 and 8 are the most common. They are provided for the sizes of accurate responsible compounds in instrument making and mechanical engineering, such as parts of internal combustion engines, cars, airplanes, metal-cutting machines, measuring instruments. The dimensions of the details of diesel locomotives, steam machines, lifting and transport mechanisms, printing, textile and agricultural machines are preferably performed on the 9th qualifies. Calital 10 is intended for the sizes of invisputable compounds, for example, for the size of the details of agricultural machinery, tractors and cars. The dimensions of the details forming the invisputable compounds in which large gaps and their oscillations are allowed, for example, the dimensions of the covers, flanges, parts obtained by casting or stamping are prescribed by 11th and 12th qualifications.

The qualifications of 13-17 are designed for the irrelevant sizes of parts that are not included in compounds with other details, i.e. for free sizes, as well as for inter-operational sizes.

Tolerances in qualitates 5-17 are determined by the general formula:

1Tq \u003d AI, (1)

where q.- qualitate number; but- a dimensionless coefficient set for each qualitate and non-nominal sized (it is called "the number of admission units"); і - a unit of admission (μm) - a multiplier depending on the nominal size;

for sizes 1-500 microns

for sizes of sv. 500 to 10,000 mm

where D. from - secondary geometric boundary values

where D. mIN. and D. max - the smallest and largest boundary value of the nominal size interval, mM..

With the specified qualit and the nominal size interval, the value of admission is constantly for shafts and holes (their tolerance fields are the same). Starting from the 5th qualitate, the tolerances in the transition to the adjacent less accurate qualitude increase by 60% (the denominator of the geometric progression is 1.6). Every five qualifications, the tolerances increase 10 times. For example, for the details of the nominal sizes of St. 1 to 3. mM.admission of the 5th qualitate IT5 \u003d 4 μm; After five qualities, it increases 10 times, i.e. IT1O \u003d .40 μmetc.

Nominal size intervals in SV bands. 3 to 180 and St. 500 to 10,000 mM.in the SST and ESDP systems coincide.

In the OST system up to 3 mM.the following dimensions intervals are installed: up to 0.01; sv. 0.01 to 0.03; sv. 0.03 to 0.06; sv. 0.06 to 0.1 (exception); from 0.1 to 0.3; sv. 0.3 to 0.6; sv. 0.6 to 1 (exception) and from 1 to 3 mM.. Interval of St. 180 to 260. mM.broken into two intermediate intervals: sv. 180 to 220 and St. 220 to 260. mM.. Interval SV.-260 to 360 mM.broken at intervals: sv. 260 to 310 and St. 310 to 360. mM.. Interval of St. 360 to 500. mM.broken at intervals: sv. 360 to 440 and sv. 440 to 500 mM..

When transferring accuracy classes to the OST in the qualifications on ESDP, you need to know the following. Since the system of tolerances was calculated in the formulas different from formulas (2) and (3), then there is no exact coincidence of admission to accuracy classes and qualitates. Initially, the accuracy classes were established in the SST system: 1; 2; 2a; 3; 3a; four; five; 7; eight; and 9. Later, the OST system was supplemented with more accurate classes 10 and 11. In the SST tolerances of the shafts 1, 2 and 2a of the accuracy classes are set smaller than for the holes of the same accuracy classes.

This is due to the difficulty of processing comparison holes with shafts.

Basic deviations

Basic deviation- One of two deviations (top or bottom) used to determine the position of the admission field relative to the zero line. Such deviation is the nearest deviation from the zero line. For fields of shaft tolerances (holes) located above the zero line, the main deviation is the lower deflection, the EI shaft (for, the holes Ei) with the "plus" sign, and for the tolerance fields located below the zero line, the main deviation is the upper deviation of the shaft Eѕ (for the hole of the Eѕ) with the "minus" sign. From the boundary of the main deflection begins the tolerance field. The position of the second border of the admission field (i.e., the second limit deviation) is defined as the algebraic amount of the value of the main deviation and admission to the qualitate of accuracy.

For the shafts installed 28 main deviations and as much basic deviations for the holes (GOST 25346 - 82). The main deviations are denoted by one or two letters of the Latin alphabet: for the shaft - with lowercase letters from A to ZC, and for the opening - with capital letters from A to ZC (Fig. 1, d). The values \u200b\u200bof the main deviations are shown in the tables.

The main deviations of the shafts from A to G (the upper deviation of the Eѕ with the "minus" sign) and the main deviation of the H shaft H (Eѕ is zero) are intended for the formation of fields of shafts in landings with a gap; From ј (ј) to N - in transitional landings from p to ZC (lower deviations of the EI with a "plus" sign) - in landings with tension. Similarly, the main deviations of the holes from A to G (the lower deviations of the EI with the "plus" sign) and the main deviation of the hole H (for it is EI \u003d 0) are designed to form field tolerance fields in landings with a gap; From ј (ј) to n - in transitional landings and from p to ZC (the upper deviations of Eѕ with the "minus" sign) - in landings with tension. Letters ј ѕ and ј ѕ designated a symmetric arrangement of admission relative to the zero line. In this case, the numeric values \u200b\u200bof the upper E * (ES) and the Nizhny EІ (EI) deviation of the shaft (holes) are numerically equal, but are opposed to the sign (the upper deviation with the "plus" sign, and, the bottom - with the "minus" sign).

The main deviations of the shaft and the holes indicated by the same name (for this size interval) are equal in size, but are opposed to the sign; They increase with an increase in the size of the size interval.

Hole system and shaft system

A combination of field tolerances and holes can be obtained a large number of landings. There are landings in the hole system and in the shaft system.

Landing in the opening system- landings in which various gaps and tension are obtained by a compound of various shafts with one basic hole (Fig. 1, a), whose admission field (for this qualitate and size interval) is constantly for the entire set of landings. The tolerance field of the main opening is consistently relatively zero

the lines so that its lower deviation is ig \u003d 0 (it is the main deviation of H), and the upper deviation of Eѕ with the sign + "plus" is numerically equal to the tolerance of the main opening. Fields of tolerances in landings with a gap are located below the zero line (under the field of tolerance of the main opening), and in landings with a tension - above the main hole tolerance fields (Fig. 1, b). In transitional landings, the shaft tolerance fields are partially or completely overlapped the main hole tolerance field.

Landing in the shaft system- landings in which various gaps and tension are obtained by a compound of various holes with one main shaft, the field of tolerance of which (for this qualitate and size interval) is constantly for the entire set of landings. The main shaft tolerance field is unchanged relative to the zero line so that its upper deviation is Eѕ \u003d 0, and the lower deviation of the EI with the sign is "minus" numerically equal to the tolerance of the main shaft. Fields of tolerances in landings with a gap are located above the main shaft tolerance fields, and in landings with a tension - below the main shaft tolerance field.

The opening system is characterized by a simpler product manufacturing technology compared to the shaft system, and therefore it has received preferential use. According to the shaft system, rolling bearings with holes of the sleeves or body housings, as well as a piston finger with piston and connecting rod, etc.

In some cases, to obtain compounds with very large gaps use combined landings- landings formed by field tolerances from the shaft system and field tolerances of the shafts from the hole system.

For nominal size less than 1 and sv. 3150 mm, as well as for the 9-12-th qualifications, at nominal sizes of 1-3150 mm, the landings are formed by combining the tolerance fields of the holes and the shafts of the same qualitate of accuracy, for example, H6 / P6; H7 / E7; E8 / H8; H9 / E9 and B11 / H1. In the 6th and 7th qualifications at nominal sizes of 1-3150 mm for technological considerations, the opening tolerance field is recommended to choose to one kill with coarser than the shaft tolerance field, for example, H7 / k6; E8 / H7.

In addition to the landings specified in the tables, in technical cases are allowed to use other landings formed from the TDP tolerance fields. Landing should refer to the hole system or the shaft system, and with unequal tolerances of the hole and the shaft, the larger tolerance should have a hole. Tolerances and shaft can differ from no more than two qualitates.

The choice and purpose of tolerances and landings is carried out on the basis of calculations of the necessary gaps or testers, taking into account the experience of the operation of such compounds.

The property of independently made details (or nodes) occupy your place in the node (or machine) without additional processing of them when assembling and perform your functions in accordance with the specifications of this node (or machine)
Incomplete or limited interchangeability is determined by the selection or additional processing of parts when assembling

Hole system

A combination of landings in which various gaps and tension are obtained by a compound of various shafts with the main hole (hole, the lower deviation of which is zero)

Vala system

The set of landings in which various gaps and tension are obtained by compounding various holes with the main shaft (shaft, the upper deviation of which is zero)

In order to increase the level of interchangeability of products, the reduction of the nomenclature of the normal tool is installed fields of shaft tolerances and holes of the preferred application.
The character of the compound (landing) is determined by the difference in the size of the hole and the shaft

Terms and definitions according to GOST 25346

The size - numerical value of the linear value (diameter, length, etc.) in the selected units of measurement

Valid size - the size of the element set by measurement

Limit dimensions - Two extremely permissible size of the element, between which should be (or which can be equal to) a valid size

The largest (smallest) limit - the largest (smallest) permissible size of the element

Nominal size - the size relative to which deviations are determined

Deviation - Algebraic difference between the size (valid or limit size) and the corresponding nominal size

Actual deviation - Algebraic difference between valid and appropriate nominal sizes

Limit deviation - Algebraic difference between the limit and corresponding nominal sizes. Distinguish the upper and lower limit deviations

Upper deviation ES, ES - Algebraic difference between the greatest limit and corresponding nominal sizes
Es - upper deviation of the hole; es - Top Deviation of Shaft

Lower deviation EI, EI - Algebraic difference between the smallest limit and corresponding nominal sizes
EI- lower hole deviation; eI - the bottom deviation of the shaft

Basic deviation - One of the two limit deviations (top or bottom), which determines the position of the tolerance field relative to the zero line. In this system of tolerances and landing, the main is the deviation nearest to the zero line

Zero line - The line corresponding to the nominal size from which the deviations of the sizes are deposited during the graphic image of the tolerance and landing fields. If the zero line is located horizontally, then positive deviations are deposited up from it, and negative - down

Tolerance T. - the difference between the greatest and lowest limits or the algebraic difference between the upper and lower deviations
Tolerance is an absolute value without a sign

Standard tolerance IT. - any of the tolerances installed by this system of tolerances and landings. (In the future, the term "tolerance" means "standard tolerance")

Field tolerance - The field limited to the greatest and lowest limits and the determined value of admission and its position relative to the nominal size. With a graphic image, the admission field is concluded between two lines corresponding to the upper and lower deviations relative to the zero line

Quality (degree of accuracy) - a set of tolerances considered as corresponding to one level of accuracy for all nominal sizes

Admission unit I, I - a multiplier in the tolerance formulas, which is a function of a nominal size and an employee to determine the numerical value of admission
i. - unit tolerance for nominal sizes up to 500 mm, I. - A unit of admission for the nominal sizes of St. 500 mm

Shaft - term conventionally used to designate outdoor elements of parts, including non-cylindrical elements

Hole - term, conditionally used to designate internal elements of parts, including non-cylindrical elements

Main Val. - shaft, the upper deviation of which is zero

Basic hole - hole, the lower deviation of which is zero

Maximum limit (minimum) material - The term belonging to that of limit sizes, which corresponds to the largest (smallest) volume of the material, i.e. The greatest (smallest) limit size of the shaft or the smallest (greatest) limiting hole

Landing - the nature of the connection of two parts, determined by the difference between their size to the assembly

Nominal planting size - Nominal size, common for the hole and shaft constituting

Tear landing - the sum of the tolerances of the opening and shaft constituting the connection

Gap - the difference between the sizes of the hole and the shaft to the assembly, if the hole size is greater than the size of the shaft

Tension - the difference between the sizes of the shaft and the holes to the assembly, if the size of the shaft is greater than the hole size
The tension can be determined as a negative difference between the dimensions of the hole and the shaft

Landing with gap - landing at which the clearance is always formed in the compound, i.e. The smallest limiting hole size is greater than the largest graft size or equal to it. With a graphic image, the opening tolerance field is located above the shaft tolerance field.

Landing with tension -the landing at which the tension is always formed in the compound, i.e. The greatest limit size of the opening is less than the smallest limit size of the shaft or equal to it. With a graphic image, the opening tolerance field is located under the shaft tolerance field.

Transient landing - landing at which it is possible to obtain both the gap and the tension in the compound, depending on the actual sizes of the opening and shaft. With a graphic image of the tolerance fields, the holes and shaft overlap completely or partially

Landing in the opening system

- landings in which the required gaps and tension are obtained by a combination of various shaft tolerance fields with the main hole tolerance field

Landing in the shaft system

- landings in which the required gaps and tension are obtained by a combination of various fields of hole tolerances with the main shaft tolerance field

Normal temperature - Tolerances and limit deviations established in this standard belong to the dimensions of parts at a temperature of 20 degrees with