The main deviation is one of the two limit, closer to the zero line (Fig. 3.1).

For the shafts there are 27 main deviations, they are denoted by the line letters of the Latin alphabet. The values \u200b\u200bof the main deviations are determined by the empirical formulas, which are shown in Table. 4 GOST 25346-89. The main deviations depend only on the size, but not from qualitate, even if the tolerance is present in the formula. As an example, we give

several formulas: D → ES \u003d - 16 D 0.44; g → es \u003d - 2.5 d 0.34; M → Ei \u003d + (IT7 - - IT6); T → Ei \u003d + IT7 + 0.63D.

The lettering J s does not have a basic deviation, its limit deviations are equal to ± it / 2, i.e. Es \u003d + IT / 2, and Ei \u003d - IT / 2.

Second deviations are calculated based on tolerance.

If the main deviation is top, then

eI \u003d ES - TD, (3.11)

and if the main is the bottom, then

eS \u003d EI + TD. (3.12)

The location of the main deviations of the holes and the shafts is shown in Fig. 3.2.

3.3. Basic deviations of holes

The main deviations of the holes are constructed in such a way as to ensure the formation of landings in the shaft system, similar to landings in the opening system. The main deviations of the holes are equal in size and are opposite to the sign of the main deviations of the shafts indicated by the same letter (Fig. 3.3). The main deviations of the holes are determined in two rules.

General rule. The main deviation of the opening must be symmetrically relative to the zero line to the main deviation of the shaft, denoted by the same letter: Ei \u003d - ES for A - H; ES \u003d - EI - for j - zc.

The rule is valid for all deviations, except for the deviations of the hole n qualifies 9 - 16 for the size of over 3 mm, they are ES \u003d 0 and for deviations to which the special rule applies.

Special Rule. Two suitable landings in the hole system and in the shaft system, in which the hole of this qualitate is connected to the shaft of the nearest more accurate qualitate, should have the same gaps or tension (for example, H7 / P6 and P7 / H6).

Special rule is valid for size intervals Over 3 mm for holes:

J, k, m, n - until the 8th qualitate inclusive;

P - ZC to the 7th qualitate inclusive.

The record of the special rule in the formula is:

Es \u003d - Ei + δ, (3.13)

where δ \u003d it n is it n-1, that is, the difference between the admission of the qualified qualifications under consideration, with which this main deflection will be conjugated and the advent of the nearest more accurate qualitate (Fig. 3.4).

JS has no basic deviation, that is, Es \u003d + IT / 2, and Ei \u003d - IT / 2.

The second deviations are determined taking into account the tolerance:

ES \u003d EI + TD; (3.14)

EI \u003d ES - TD. (3.15)

3.4. Landing in ESDP

The surfaces on which the connection is connected, are called landing or matchy, all other surfaces are called free or unparabered. The sizes corresponding to these surfaces are similar: landing and free.

Landing It is called the character of the connection of parts, determined by the size of the obtained gaps or testes. Landing determines the freedom of relative movement of the mating parts relative to each other. The type of landing is determined by the magnitude and mutual arrangement of the tolerance of the hole and shaft. All landings are divided into three groups: movable, fixed and transition.

The hole and shaft, regardless of the landing and tolerances on the size, have the same comparison size, that is, the nominal size of the same (D \u003d D).

To the main

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
(by 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?

Basic concepts and terms are regulated by GOS 25346-89.

The size - numerical value of the linear value (diameter, length, etc.). Valid Call the size set by measuring with a permissible error.

Two extremely permissible size, between which should be or which can be equal to the valid size, are called limit sizes. More of them called the greatest limit sizesmaller the lowest limit size.

Nominal size - The size that serves as the beginning of the reference of deviations and relative to which the limit dimensions determine. For parts that make up the compound, the nominal size is common.

Not any size obtained as a result of the calculation can be accepted for nominal. To increase the level of interchangeability, reduce the nomenclature of products and sizes of blanks, standard or normalized cutting and measuring instruments, equipment, and calibers, create conditions for specialization and cooperation of enterprises, cheapening products, the size of the size obtained by the calculation should be rounded in accordance with the values \u200b\u200bspecified in Guest 6636-69. At the same time, the initial value of the size obtained by calculating or otherwise, if it differs from the standard one, it should be rounded to the nearest larger standard size. The standard for normal linear dimensions is based on the base of the preferred numbers of GOST 8032-84.

The most widely used series of preferred numbers, built according to geometric progression. Geometric progression provides rational gradation of the numerical values \u200b\u200bof parameters and sizes when you need to install more than one value, but a uniform number of values \u200b\u200bin a specific range. In this case, the number of members of the series is obtained by less compared to arithmetic progress.

Recovery:

D.(d.) – nominal hole size (shaft);

D. MAX, ( d. M ah), D. min, ( d. min) , D. E ( d. E) D M.(d M.) - The sizes of the hole (shaft), the largest (maximum), the smallest (minimum), valid, medium.

Es(es) - upper limit deviation of the hole (shaft);

El.(eI) - lower limit deviation of the hole (shaft);

S, S. Max , S. MIN. , S. M - gaps, the largest (maximum), the smallest (minimum), average, respectively;

N., N. MAX, N. min N. M. – tension, the largest (maximum), the smallest (minimum), medium, respectively;

TD, TD, TS, TN, TSN- tolerances of the hole, shaft, gap, tension, gap - tension (in the transitional landing), respectively;

IT.1, IT.2, IT.3…ITN.……IT.18 - qualitate tolerances are designated by a combination of letters. IT.with a sequence number of qualitate.

Deviation - Algebraic difference between the size (valid, limit, etc.) and the corresponding nominal size:

For hole Es = D. Max - D.; EI = D. min - D.;

For Vala. es = d. Max - d.; eI = d. min - d..

Actual deviation - Algebraic difference between valid and nominal sizes. The deviation is positive, if the valid size is greater than the nominal and negative, if it is less than the nominal. If the actual size is equal to the nominal, then its deviation is zero.

Limit deviation The algebraic difference between the limit and nominal sizes is called. Distinguish the upper and lower deviations. Top deviation - Algebraic difference between the largest limit and nominal sizes. Lower deviation - Algebraic difference between the lowest limit and nominal sizes.

For simplification and convenience of work in the drawings and in standards tables for tolerances and landing instead of limit sizes, it is customary to affix the values \u200b\u200bof limit deviations: upper and lower. Deviations always indicate with the "+" or "-" sign. The upper limit deviation is set slightly above the nominal size, and the lower is slightly lower. Deviations equal to zero are not affixed in the drawing. If the upper and lower limit deviations are equal in an absolute value, but are opposed to the sign, the numeric value of the deviation indicate the "±" sign; The deviation indicates after the nominal size. For example:

thirty ; 55; 3 +0.06; 45 ± 0.031.

Basic deviation - One of the two deviations (top or bottom) used to determine the tolerance field relative to the zero line. Usually, such deviation 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 tolerances and landings. If the zero line is horizontally, the positive deviations are deposited up from it, and negative - down.

Size tolerance - The difference between the greatest and lowest limits or the absolute value of the algebraic difference between the upper and lower disabilities:

For hole TD.= D. Max - D. mi. n. = Es – EI;

For Vala. TD \u003d D. Max - d. MIN. \u003d ES - EI.

The tolerance is a measure of size accuracy. The less the tolerance, the higher the required accuracy of the part, the smaller the vibration of the actual size of the part is allowed.

When processing, each detail acquires its valid size and can be evaluated as suitable if it is in the limiting range, or rejected if the actual size came out for these boundaries.

The conditionality condition of the details can be expressed by the following inequality:

D. Max ( d. MAX) ≥ D. E ( d. e) ≥ D. min ( d. min).

The tolerance is a measure of size accuracy. The smaller the tolerance, the smaller the permissible oscillation of the real size, the higher the accuracy of the part and, as a result, increases the complexity of processing and its cost

Field tolerance - A field limited to the upper and lower disabilities. The tolerance field is determined by the numerical value of the tolerance 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 (Figure 1.1).

Figure 1.1 - Tolerance field location schemes:

but - holes ( Es and EI - positive); b. - Shaft ( es and eI - Negative)

In the conjunction of parts included in the other, there are covering and covered surfaces. Shaft - The term applied to designate outdoor (covered) parts elements. Hole - The term conventionally used to designate internal (covering) elements of parts. The terms hole and shaft refer not only to cylindrical parts of the circular cross section, but also to the elements of the details of another shape, for example, a limited two parallel plane.

Main Val. - shaft, the upper deviation of which is zero ( es= 0).

Basic hole - hole, the lower deviation of which is zero ( EI= 0).

Gap - difference in the size of the hole and shaft, if the size of the opening is greater than the shaft size. The gap provides the possibility of relative movement of the assembled parts.

Tension - The difference in the size of the shaft and holes to the assembly, if the size of the shaft is greater than the hole size. The tension provides mutual immobility of parts after their assembly.

The greatest and smallest gaps (tension) - Two limit values, between which the gap should be (tension).

Medium gap (tension) There are arithmetic averages between the greatest and lowest gap (tension).

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

Landing with gap - landing at which the gap is always ensured.

In landings with a gap, the opening tolerance field is located above the shaft tolerance field. The landings with the gap also include landings, in which the lower border of the hole tolerance field coincides with the upper boundary of the shaft tolerance field.

Landing with tension - landing at which the tension is always ensured in the connection. In landings with a tension, the opening tolerance field is located under the shaft tolerance field.

Transitional landing It is called landing at which it is possible to obtain both the gap and the tension in the compound. In such a landing, the tolerances of the hole and shaft are completely or partially overlap each other.

Tear landing - The sum of the tolerances of the hole and the shaft constituting the connection.

Factory Characteristics:

For landing with a gap:

S. min \u003d D. min - d. Max \u003d. EI – es;

S. Max \u003d. D. Max - d. min \u003d Es – eI;

S. m \u003d 0.5 ( S. Max +. S. min);

TS = S. Max - S. min \u003d TD. + TD.;

For landing with tension:

N. min \u003d d. min - D. Max \u003d. eI – Es;

N. Max \u003d. d. Max - D. min \u003d es – EI;

N. m \u003d 0.5 ( N. Max +. N. min);

TN = N. Max - N. min \u003d TD. + TD.;

For transitional landings:

S. Max \u003d. D. Max - d. min \u003d Es – eI;

N. Max \u003d. d. Max - D. min \u003d es – EI;

N. M ( S. m) \u003d 0.5 ( N. Max - S. MAX);

the result with a minus sign would mean that the average value for landing corresponds to S. m.

TS(N.) = TN(S.) = S. Max +. N. Max \u003d. TD. + TD..

In engineering and instrument making, landings of all three groups are widely used: with a gap, tension and transition. Landing any group can be obtained, or changing the size of both mating parts, or one conjugate part.

The set of landings in which the limit deviations of the holes of one nominal size and one accuracy are the same, and various landings are achieved by changing the limit deviations of the shafts, called system hole. For all landings in the opening system lower hole deviation EI\u003d 0, i.e., the lower limit of the main hole tolerance field coincides with the zero line.

The set of landings in which the limit deviations of the shaft of one nominal size and one accuracy are the same, and various landings are achieved by changing the limit deviations of the holes, called system Vala.. For all landings in the shaft system, the upper deviation of the main shaft es\u003d 0, i.e. the upper limit of the shaft tolerance field always coincides with the zero line.

Both systems are equal and have about the same nature of the same landings, i.e., limit clearances and tension. In each case, the choice of one or another system is influenced by design, technological and economic considerations. At the same time, it should be paid to the fact that the exact shafts of different diameters can be processed on the machines with one tool when changing only the machine setup. The exact holes are processed by a measuring cutting tool (cenks, sweeps, broach, etc.), and for each hole size, a tool kit is required. In the hole system of various over the limit sizes of the holes many times less than in the shaft system, and, therefore, the nomenclature of an expensive tool is reduced. Therefore, the prevalence of the opening was obtained. However, in some cases you have to use the shaft system. We present some examples of the preferred application of the shaft system:

In order to avoid the concentration of stresses at the place of transition from one diameter to another, the step shaft is undesirable to the other on the strength considerations, and then constant diameter is performed;

When repairing, when there is a finished shaft and a hole is made under it;

According to technological reasons when the cost of manufacturing the shaft, for example, on power-grinding machines is small, it is advantageous to apply the shaft system;

When using standard nodes and parts. For example, the outer diameter of rolling bearings is manufactured according to the shaft system. If you do the outer diameter of the bearing in the hole system, it would be necessary to significantly expand their nomenclature, and the bearing on the outer diameter is impractical;

When one diameter shaft is needed to install multiple holes with different types of landings.

Similar information.

Designations:

· IT \u003d INTERNATIONAL TOLERANCE;

· Upper and lower deviations, ES \u003d ECART SUPERIEUR, EI \u003d ECART INTERIEUR,

· For holes Large letters (ES, D), for small shafts (ES, D).

Diagram of the tolerance of the hole. According to the drawing - 4 mm, limit dimensions - 4.1-4.5. In this case, the tolerance field does not intersect the zero line, since both limit size is higher than the nominal.

The main terms and definitions of GOST 25346-89.

· Shaft - The term conventionally used for the designations of external elements of parts, including non-cylindrical elements.

· Hole - The 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.

• Valid size - The size of the element set by the measurement.
• Limit dimensions - Two maximum permissible element size, between which should be (or which can be equal to) a valid size.
• 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. There are upper and lower limit deviations.
• Upper deviation ES, ES - Algebraic difference between the highest limit and corresponding nominal sizes.

Note. Es - upper deviation of the hole; es - Top deviation of the shaft.

• Lower deviation EI, EI - Algebraic difference between the smallest limit and corresponding nominal sizes.

Note. EI - lower hole deviation; eI - Bald shaft deviation.

• 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 landings, 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 horizontally, the positive deviations are deposited up from it, and negative - down.

· Tolerance T. - The difference between the greatest and lowest limits or an algebraic difference between the upper and lower disabilities.

Note. Admission is an absolute value without a sign.

· Standard tolerance IT. - any of the tolerances installed by this system of tolerances and landings.

· 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 the 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.

Note. i. - unit tolerance for nominal sizes up to 500 mm, I. - A unit of admission for the nominal sizes of St. 500 mm.

Linear dimensions, angles, surface quality, material properties, specifications are indicated.

Tolerance

• 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 the measurement.
• Limit dimensions - Two maximum permissible element size, between which should be (or which can be equal to) a valid size.
• 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. There are upper and lower limit deviations.
• Upper deviation ES, ES - Algebraic difference between the highest limit and corresponding nominal sizes.

Note. Es - upper deviation of the hole; es - Top deviation of the shaft.

• Lower deviation EI, EI - Algebraic difference between the smallest limit and corresponding nominal sizes.

Note. EI - lower hole deviation; eI - Bald shaft deviation.

• 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 landings, 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 horizontally, the positive deviations are deposited up from it, and negative - down.
• Tolerance T. - The difference between the greatest and lowest limits or an algebraic difference between the upper and lower disabilities.

Note. Admission is an absolute value without a sign.

• Standard tolerance IT. - any of the tolerances installed by this system of tolerances and landings.
• 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 the 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.

Note. i. - unit tolerance for nominal sizes up to 500 mm, I. - A unit of admission for the nominal sizes of St. 500 mm.

• Shaft - The term conventionally used for the designations of external elements of parts, including non-cylindrical elements.
• Hole - The 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.
• Landing-Character connecting two parts, determined by the difference between their size to the assembly.
• Nominal planting size-noal size, common for the hole and shaft constituting the connection.
• Tear landing-Summage tolerances of the hole and shaft constituting the connection.
• Gap- The quality between the sizes of the hole and the shaft to the assembly, if the size of the opening is greater than the size of the shaft

Linear dimensions, corners, surface quality, material properties, specifications

Linear dimensions, corners, surface quality, material properties, specifications are indicated:

To eliminate an excessive manifold, numerical values \u200b\u200bare recommended to be applied (for example, rounding the calculated values) with preferred numbers. Based on rows of preferred numbers developed rows of normal linear sizes (GOST 6636-69). Normal linear dimensions, mm:

3,2	3,4	3,6	3,8	4,0	4,2	4,5	4,8	5,0	5,3
5,6	6,0	6,3	6,7	7,1	7,5	8,0	8,5	9,0	9,5
10	10,5	11	11,5	12	13	14	15	16	17
18	19	20	21	22	24	25	26	28	30
32	34/35	36	38	40	42	45/47	48	50/52	53/55
56	60/62	63/65	67/70	71/72	75	80	85	90	95
100	105	110	120	125	130	140	150	160	170
180	190	200	210	220	240	250	260	280	300
320	340	360	380	400	420	450	480	500	530
560	600	630	670	710	750	800	850	900	950

Note: Under the oblique feature shows the size of the seats for rolling bearings.

Termination of the corner of the cone

The limit deviation of the corner of the cone: 1) if the cone is set by tappingity is denoted by symbols and numerical value of the degree of accuracy; 2) If the cone is set to the angle is denoted by symbols and the numerical value of the degree of accuracy.

Shape tolerance and location of surfaces

The tolerance of the shape and the location of the surfaces is indicated as a conventional designation (graphically with the numeric value of the tolerance) or text.

Signs of types of tolerances forms and location of surfaces

Group admission	Type of tolerance	Sign
Shape tolerance	Admission straightness
	Facility tolerance
	Tolerance roundness
	Tolerance of cylindrical
	Adjusting a longitudinal section
Admission location	Parallel tolerance
	Admission perpendicularity
	Tolerance
	Accessibility
	Symmetrical tolerance
	Position tolerance
	Accessing axes
Summary tolerance of form and location	Radial beating tolerance endless Batings in a given direction
	Tolerance of complete radiality Full end beyon
	Tolerance of the form of a given profile
	Tolerance of the form of a given surface

Quality

Quality is a measure of accuracy. With an increase in the qualitate accuracy decreases (the tolerance increases).

The value of tolerances for the size of the main opening to 500 mm:

Size, mm.	Tolerance, μm when qualify
	01	0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17
Until 3	0,3	0,5	0,8	1,2	2	3	4	6	10	14	25	40	60	100	140	250	400	600	1000
3-6	0,4	0,6	1	1,5	2,5	4	5	8	12	18	30	48	75	120	180	300	480	750	1200
6-10	0,4	0,6	1	1,5	2,5	4	6	9	15	22	36	58	90	150	220	360	580	900	1500
10-18	0,5	0,8	1,2	2	3	5	8	11	18	27	43	70	110	180	270	430	700	1100	1800
18-30	0,6	1	1,5	2,5	4	6	9	12	21	33	52	84	130	210	330	520	840	1300	2100
30-50	0,6	1	1,5	2,5	4	7	11	16	25	39	62	100	160	250	390	620	1000	1600	2500
50-80	0,8	1,5	2	3	5	8	13	19	30	46	74	120	190	300	460	740	1200	1900	3000
80-120	1	1,5	2,5	4	6	10	15	22	35	54	87	140	220	350	540	870	1400	2200	3500
120-180	1,2	2	3,5	5	8	12	18	25	40	63	100	160	250	400	630	1000	1600	2500	4000
180-250	2	3	4,5	7	10	14	20	29	46	72	115	185	290	460	720	1150	1850	2900	4600
250-315	2,5	4	6	8	12	16	23	32	52	81	130	210	320	520	810	1300	2100	3200	5200
315-400	3	5	7	9	13	18	25	36	57	89	140	230	360	570	890	1400	2300	3600	5700
400-500	4	6	8	10	15	20	27	40	63	97	155	250	400	630	970	1550	2500	4000	6300

see also

Notes

Literature

• A. I. Yakushev, L. N. Vorontsov, N. M. Fedotov. Interchangeability, standardization and technical measurements. 6th ed., Pererab. and add .. - M.: Mechanical Engineering, 1986. - 352 p.

Links

• Quality and roughness of the surfaces of holes and shafts in the hole system depending on the accuracy class

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Synonyms:

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