Basic terms and definitions
State standards(GOST 25346-89, GOST 25347-82, GOST 25348-89) replaced the OST system of tolerances and landings, which was in effect until January 1980.
Terms are given according to GOST 25346-89"Basic norms of interchangeability. Unified system of tolerances and landings".
Shaft- a term conventionally used to refer to the external elements of parts, including non-cylindrical elements;
Hole- a term conventionally used to refer to internal elements of parts, including non-cylindrical elements;
main shaft- shaft, the upper deviation of which is equal to zero;
Main hole- hole, lower deviation which is equal to zero;
The size - numerical value linear value (diameter, length, etc.) in the selected units of measurement;
actual size- the size of the element, established by the measurement with the allowable accuracy;
Nominal size- the size relative to which deviations are determined;
Deviation- algebraic difference between the size (actual or limit size) and the corresponding nominal size;
quality- a set of tolerances considered as corresponding to the same level of accuracy for all nominal sizes;
Landing- the nature of the connection of two parts, determined by the difference in their sizes before assembly.
Gap- this is the difference between the dimensions of the hole and the shaft before assembly, if the hole is larger than the size of the shaft;
Preload- the difference between the dimensions of the shaft and the hole before assembly, if the size of the shaft is larger than the size of the hole;
fit tolerance- the sum of the tolerances of the hole and the shaft that make up the connection;
Tolerance T- the difference between the largest and smallest limit sizes or the algebraic difference between the upper and lower deviations;
Standard IT approval- any of the tolerances established by this system of tolerances and landings;
Tolerance field- a field limited by the largest and smallest limit sizes and determined by the tolerance value and its position relative to the nominal size;
Landing with clearance- landing, in which a gap is always formed in the connection, i.e. the smallest limit size of the hole is greater than or equal to the largest limit size of the shaft;
Interference landing- landing, in which an interference is always formed in the connection, i.e. the largest hole size limit is less than or equal to the smallest shaft size limit;
transition fit- landing, in which it is possible to obtain both a gap and an interference fit in the connection, depending on the actual dimensions of the hole and shaft;
Landings in the hole system- landings in which the required clearances and interferences are obtained by combining different shaft tolerance fields with the tolerance field of the main hole;
Fits in the shaft system- landings in which the required clearances and interferences are obtained by combining different hole tolerance fields with the tolerance field of the main shaft.
Tolerance fields and their corresponding limit deviations are set by different ranges of nominal sizes:
up to 1 mm- GOST 25347-82;
from 1 to 500 mm- GOST 25347-82;
over 500 to 3150 mm- GOST 25347-82;
over 3150 up to 10.000 mm- GOST 25348-82.
GOST 25346-89 establishes 20 qualifications (01, 0, 1, 2, ... 18). Qualities from 01 to 5 are intended primarily for calibers.
The tolerances and limit deviations set in the standard refer to the dimensions of the parts at a temperature of +20 o C.
Installed 27
basic shaft deviations and 27
main hole deviations. The main deviation is one of two limit deviations(upper or lower), which determines the position of the tolerance field relative to the zero line. The main deviation is the closest to the zero line. The main deviations of the holes are indicated by capital letters of the Latin alphabet, shafts - lowercase. The layout of the main deviations, indicating the qualifications in which it is recommended to use them, for sizes up to 500
mm is shown below. The shaded area refers to holes. The scheme is shown in abbreviation.
Appointment of landings. Landings are chosen depending on the purpose and operating conditions of the equipment and mechanisms, their accuracy, assembly conditions. At the same time, it is necessary to take into account the possibility of achieving accuracy when various methods product processing. First of all, preferred landings should be applied. Basically, landings are used in the hole system. Shaft system fits are useful when using some standard parts (for example, rolling bearings) and in cases where a shaft of constant diameter is used along its entire length to install several parts on it with various landings.
The tolerances of the hole and the shaft in the fit should not differ by more than 1-2 quality. A larger tolerance is usually assigned to the hole. Clearances and interferences should be calculated for most types of connections, especially for interference fits, fluid friction bearings and other fits. In many cases, fits can be assigned by analogy with previously designed products that are similar in terms of working conditions.
Application examples of fits, mainly related to the preferred fits in the hole system in sizes 1-500 mm.
Landings with clearance. hole combination H with shaft h(sliding fits) are used mainly in fixed joints when frequent disassembly is necessary (replacement parts), if you need to easily move or rotate parts relative to one another when setting up or adjusting, to center fixed parts.
Landing H7/h6 apply:
For interchangeable gears in machine tools;
- in connections with short working strokes, e.g. for shanks spring valves in guide bushings (fit H7/g6 also applies);
- for connecting parts that should move easily when tightened;
- for precise guidance in reciprocating movements (piston rod in pump guide bushings high pressure);
- for centering housings for rolling bearings in equipment and various machines.
Landing H8/h7 used for centering surfaces with reduced alignment requirements.
Landings H8 / h8, H9 / h8, H9 / h9 are used for fixed parts with low requirements for the accuracy of mechanisms, light loads and the need to ensure easy assembly(gear wheels, couplings, pulleys and other parts connected to the shaft with a key; rolling bearing housings, centering of flange joints), as well as in moving joints with slow or rare translational and rotational movements.
Landing H11/h11 used for relatively roughly centered fixed joints (centering of flange covers, fixing overhead conductors), for non-critical hinges.
Landing H7/g6 it is characterized by a minimum guaranteed gap compared to the rest. They are used in movable joints to ensure tightness (for example, a spool in the sleeve of a pneumatic drilling machine), accurate direction or for short strokes (valves in a valve box), etc. Landings are used in especially precise mechanisms h6/g5 and even H5/g4.
Landing H7/f7 used in plain bearings at moderate and constant speeds and loads, including in gearboxes; centrifugal pumps; for gear wheels rotating freely on shafts, as well as wheels switched on by couplings; for guiding pushers in internal combustion engines. A more precise fit of this type - H6/f6- used for precise bearings, distributors of hydraulic transmissions of passenger cars.
Landings H7/e7, H7/e8, H8/e8 and H8/e9 used in bearings at high speeds (in electric motors, in the gear mechanism of an internal combustion engine), with spaced supports or a long mating length, for example, for a gear block in machine tools.
Landings H8/d9, H9/d9 they are used, for example, for pistons in the cylinders of steam engines and compressors, in the joints of valve boxes with the compressor housing (a large gap is required to dismantle them due to the formation of soot and significant temperature). More accurate fits of this type -H7 / d8, H8 / d8 - are used for large bearings at high speeds.
Landing H11/d11 it is used for mobile joints operating in dusty and muddy conditions (assemblies of agricultural machines, railway cars), in swivel joints of rods, levers, etc., for centering steam cylinder covers with sealing of the joint with ring gaskets.
Transition landings. Designed for fixed connections of parts subjected to assembly and disassembly during repairs or operating conditions. The mutual immobility of the parts is ensured by keys, pins, pressure screws, etc. Less tight fits are prescribed if necessary in frequent disassembly of the connection, in case of inconvenience, high centering accuracy is required, with shock loads and vibrations.
Landing H7/n6(deaf type) gives the most durable connections. Application examples:
For gears, couplings, cranks and other parts under heavy loads, shocks or vibrations in joints that are usually disassembled only when overhaul;
- landing adjusting rings on the shafts of small and medium-sized electric machines; c) landing of conductor bushings, locating pins, pins.
Landing H7/k6(tension type) on average gives a slight gap (1-5 microns) and provides good centering, without requiring significant effort for assembly and disassembly. It is used more often than other transitional landings: for landing pulleys, gears, couplings, flywheels (on keys), bearing bushings.
Landing h7/js6(dense type) has larger average gaps than the previous one, and is used instead of it, if necessary, to facilitate assembly.
Landings with interference. The choice of landing is made from the condition that, at the least interference, the strength of the connection and transmission, loads are ensured, and at the greatest interference, the strength of the parts.
Landing H7/r6 are used for relatively small loads (for example, fitting a sealing ring on the shaft, which fixes the position of the inner ring of the bearing in crane and traction motors).
Landings H7/r6, H7/s6, H8/s7 used in connections without fasteners under small loads (for example, a sleeve in the head of a connecting rod of a pneumatic engine) and with fasteners under heavy loads (fitting gears and couplings on a key in rolling mills, oil drilling equipment, etc.).
Landings H7/u7 and H8/u8 used in joints without fasteners under significant loads, including alternating ones (for example, connecting a pin with an eccentric in the cutting apparatus of agricultural harvesting machines); with fasteners at very high loads (fitting of large couplings in rolling mill drives), at light loads, but a short mating length (valve seat in the cylinder head truck, bushing in the combine harvester cleaning lever).
High Precision Interference Fits H6/r5, H6/r5, H6/s5 they are used relatively rarely and in joints that are especially sensitive to interference fluctuations, for example, the landing of a two-stage bushing on the armature shaft of a traction motor.
Tolerances for incompatible dimensions. For non-matching dimensions, tolerances are assigned depending on functional requirements. Tolerance fields usually have:
- in the "plus" for holes (denoted by the letter H and the quality number, for example, HZ, H9, H14);
- in "minus" for shafts (denoted by the letter h and the quality number, for example h3, h9, h14);
- symmetrical about the zero line ("plus - minus half of the tolerance" denote, for example, ±IT3/2, ±IT9/2, ±IT14/2). Symmetrical tolerances for holes can be marked with the letters JS (eg JS3, JS9, JS14) and for shafts with the letters js (eg js3, js9, js14).
Tolerances for 12-18 The th qualification is characterized by non-conjugated or conjugated dimensions of relatively low accuracy. Repeatedly repeating limit deviations in these qualifications are allowed not to be indicated in the dimensions, but to be stipulated by a general entry in the technical requirements.
For sizes from 1 to 500 mm
Preferred Fits placed in a frame.
Electronic table of hole and shaft tolerances with indication of fields according to old system OST and ESDP.
Full table tolerances and fits of smooth joints in the hole and shaft systems, indicating the tolerance fields according to the old OST system and according to the ESDP:
Related Documents:
Angle Tolerance Tables
GOST 25346-89 "Basic standards of interchangeability. Unified system of tolerances and fits. General provisions, series of tolerances and basic deviations "
GOST 8908-81 "Basic norms of interchangeability. Normal angles and corner tolerances
GOST 24642-81 "Basic norms of interchangeability. Tolerances of the shape and location of surfaces. Basic terms and definitions"
GOST 24643-81 "Basic norms of interchangeability. Tolerances of the shape and location of surfaces. Numerical values"
GOST 2.308-79 "Unified system design documentation. Indication on the drawings of the tolerances of the shape and location of surfaces "
GOST 14140-81 "Basic standards of interchangeability. Tolerances for the location of the axes of holes for fasteners"
A unified system of tolerances and fits (ESDP) for smooth elements of parts (cylindrical or limited by parallel planes) with nominal sizes up to 3150 mm is established by GOST 25346-82 (ST SEV 145-75) and GOST 25347-82 (ST SEV 144-75). Further development ESDP received in GOST 25348-82 (ST SEV 177-75) for sizes over 3150 mm and GOST 25349-82 (ST SEV 179-75).
GOST 25346-82 (ST SEV 145-75) establishes terms and definitions in the field of tolerances and landings.
The size- numerical value of a linear quantity (diameter, length, etc.) in the selected units.
actual size- the size established by measurement with an allowable error.
Limit dimensions- two limit allowable size, between which there must be (or which may be equal to) the actual size. Maximum size limit- the larger of the two dimensions. Smallest size limit is the smaller of the two sizes.
Rated the size is called, with respect to which the limiting dimensions are determined and which also serves as the starting point for deviations.
Upper limit deviation- algebraic difference between the largest limit and nominal sizes. Lower limit deviation- algebraic difference between the smallest limit and nominal sizes.
Zero line- the line corresponding to the nominal size, from which the dimensional deviations are plotted at graphic image permits and landings. If the zero line is located horizontally, then positive deviations are laid up from it, and negative deviations are laid down.
Tolerance- the difference between the largest and smallest limit sizes. Tolerance field- field limited by the upper and lower limit deviations.
Basic deviation- one of two limit deviations (upper or lower) used to determine the position of the tolerance field relative to the zero line. In the ESDP CMEA, the main deviation is the closest to the zero line.
The deviation is indicated by one or two letters of the Latin alphabet: lowercase for shafts and uppercase for holes, for example, ES - upper deviation of the hole; es - upper deviation of the shaft; EI - lower hole deviation; ei - lower shaft deviation.
The designation of the size tolerance field is formed by a combination of the designation of the main deviation (one or two letters) and the quality (one or two numbers), which are written after the nominal size, for example: 40g6; 0.2EF7.
Tolerance fields for non-critical dimensions can be one-sided (for holes - H; for shafts - h) or symmetrical (for holes - Js; for shafts - js, for sizes not related to holes and shafts - ± IT / 2).
Quality (instead of the previously used term accuracy class) - the degree of gradation of system tolerance values. Each qualification contains a number of tolerances, which in the system of tolerances and landings are considered as corresponding to approximately the same accuracy for all nominal sizes. 19 qualifications are established: 01; 0; one; 2; ...; 17, Qualities 01; 0; one; ...; 5 are intended primarily for calibers.
The table below shows a comparison of the ESDP qualifications with the OST accuracy classes. (Never seen OST used)
| quality | Accuracy class ost | |
|---|---|---|
| main hole | main shaft | |
| 5 | - | 1 |
| 6 | 1 | 2 |
| 7 | 2 | |
| - | 2a | |
| 8 | 2a | |
| 3 | ||
| 9 | 3 | |
| 3a | ||
| 10 | 3a | |
| 11 | 4 | |
| 12 | 5 | |
| 13 | 5 | |
| 7 | ||
| 14 | 7 | |
| 15 | 8 | |
| 9 | ||
| 16 | 9 | |
| 10 | ||
| 17 | 11 | |
Tolerances and fits of smooth cylindrical elements of parts
Shaft- a term used to refer to the external (covered) elements of a part.
Hole- a term used to refer to the internal (covering) elements of a part.
A comparison of the tolerance fields of the ESDP and the replaceable tolerance fields of the OST for holes and shafts in the hole system is given in Tables 2 and 3, and for holes and shafts in the shaft system - in Tables 4 and 5. A comparison of the tolerance fields of irresponsible sizes (with large tolerances) is given in table 6.
| Tolerance field ESDP | Replaceable OST tolerance field | Tolerance field ESDP | Replaceable OST tolerance field |
|---|---|---|---|
| h3 | From 07 | k4 | H 08 |
| g3 | D 07 | j s 4 | P 08 |
| h4 | From 08 | n5 | G 1 |
| g4 | D 08 | m5 | T 1 |
| h5 | From 1 | k5 | H 1 |
| g5 | D 1 | j s 5 | P 1 |
| f6 | X 1 | n6 | G |
| h6 | FROM | m6 | T |
| g6 | D | k6 | H |
| f7 | X | j s 6 | P |
| e8 | L | n7 | G 2a |
| d8 | W | m7 | T 2a |
| c8 | TX | k7 | H 2a |
| h7 | C 2a | j s 7 | P 2a |
| f8 | X 2a | n3 | PR2 07 |
| h8; h9 | From 3 | m3 | Pr1 07 |
| f9; (e9) | X 3 | p4 | Pr2 08 |
| d9; (d10) | Sh 3 | n4 | Pr1 08 |
| h10 | C 3a | s5 | Pr2 1 |
| h11 | From 4 | r5 | Pr1 1 |
| d11 | X 4 | u7 | Gr |
| c11; b11 | L 4 | r6; s6 | Etc |
| b11; a11 | Sh 4 | p6; r6 | Pl |
| h12 | From 5 | u8 | Pr2 2a |
| b12 | X 5 | s7 | Pr1 2a |
| k3 | H 07 | r8; x8; u8 | Pr3 3 |
| j s 3 | P 07 | x8; u8 | Pr2 3 |
| m4 | G 08 | u8; s7 | Pr1 3 |
| Tolerance field ESDP | Replaceable OST tolerance field | Tolerance field ESDP | Replaceable OST tolerance field |
|---|---|---|---|
| H4 | From 08 | M4 | G 08 |
| G4 | D 08 | K4 | H 08 |
| H5 | From 09 | J s 4 | P 08 |
| G5 | D 09 | M5 | G 09 |
| H6 | From 1 | K5 | H 09 |
| G6 | D 1 | J s 5 | P 09 |
| F7 | X 1 | N6 | G 1 |
| H7 | FROM | M6 | T 1 |
| G7 | D | K6 | H 1 |
| F8 | X | Js6 | P 1 |
| E8 | L | N7 | G |
| D8 | W | M7 | T |
| H8 | C 2a | K7 | H |
| H8; H9 | From 3 | J s 7 | P |
| (F9); E9 | X 3 | N8 | G 2a |
| D9; (D10) | Sh 3 | M8 | T 2a |
| H10 | C 3a | K8 | H 2a |
| H11 | From 4 | Js8 | P 2a |
| D11 | X 4 | N4 | Pr1 08 |
| C11; B11 | L 4 | N5 | Pr1 09 |
| B11; A11 | Sh 4 | U8 | Gr |
| H12 | From 5 | R7; S7 | Etc |
| B12 | X 5 | U8 | Pr2 2a |
When manufacturing parts that will have interfaces with each other, the designer takes into account the fact that these parts will have errors and will not fit perfectly to each other. The designer determines in advance in what range the errors are allowed. Installed 2 sizes for each mating part, minimum and maximum value. Within this range, the size of the part must be located. The difference between the largest and smallest limit sizes is called admission.
Particularly critical tolerances manifest themselves in the design of the dimensions of the seats for the shafts and the dimensions of the shafts themselves.
Maximum part size or upper deviation ES, es- the difference between the largest and nominal size.
Minimum size or lower deviation EI, ei- the difference between the smallest and nominal size.
Landings are divided into 3 groups depending on the selected tolerance fields for the shaft and hole:
- With a gap. Example:
- with interference. Example:
- transitional. Example:
Tolerance fields for landings
For each group described above, there are a number of tolerance fields in accordance with which a shaft-hole interface group is made. Each individual tolerance field solves its specific task in a specific area of industry, which is why there are so many of them. Below is a picture of the types of tolerance fields: 
The main deviations of the holes are indicated in capital letters, and the shafts - lowercase.
There is a rule for the formation of a shaft-hole fit. The meaning of this rule is as follows - the main deviations of the holes are equal in magnitude and opposite in sign to the main deviations of the shafts, indicated by the same letter.
The exception is connections intended for pressing or riveting. In this case, for the shaft tolerance field, the closest value of the hole tolerance field is selected.
The totality of tolerances or qualifications
quality- a set of tolerances considered as corresponding to the same level of accuracy for all nominal sizes.
The qualification implies that the workpieces fall into the same accuracy class, regardless of their size, provided that the manufacture of different parts is carried out on the same machine, and under the same technological conditions, with the same cutting tools.
There are 20 qualifications (01, 0 - 18).
The most accurate qualifications are used for the manufacture of samples of measures and calibers - 01, 0, 1, 2, 3, 4.
The qualifications used for the manufacture of mating surfaces must be accurate enough, but in normal conditions special accuracy is not required, therefore, for these purposes, qualifications 5 to 11 are used.
From 11 to 18, qualifications are not very accurate and their use is limited in the manufacture of non-matching parts.
Below is a table of accuracy by qualifications.
The difference between tolerances and qualifications
There are still differences. Tolerances are the theoretical deviations margin of error within which it is necessary to make a shaft - a hole, depending on the purpose, the size of the shaft and the hole. quality or is the degree manufacturing accuracy mating surfaces shaft - hole, these are actual deviations, depending on the machine or the method of bringing the surface of the mating parts to the final stage.
For example. It is necessary to make a shaft and a seat for it - a hole with a tolerance field of H8 and h8, respectively, taking into account all factors, such as the diameter of the shaft and hole, working conditions, product material. Let's take the diameter of the shaft and the hole 21mm. With a tolerance of H8, the tolerance field is 0 + 33 µm and h8 + -33 µm. in order to get into this tolerance field, you need to select a quality or manufacturing accuracy class. We take into account that during the manufacture on the machine, the unevenness of the manufacture of the part can deviate both in the positive and in the negative direction, therefore, taking into account the tolerance field H8 and h8, it was 33/2 = 16.5 μm. This value corresponds to all qualifications up to 6 inclusive. Therefore, we choose a machine and a processing method that allows us to achieve an accuracy class corresponding to the 6th grade.
qualifications form the basis of the current system of tolerances and landings. quality is a set of tolerances that, for all nominal sizes, correspond to the same degree of accuracy.
Thus, we can say that it is the qualifications that determine how accurately the product as a whole or its individual parts are made. The name of this technical term comes from the word " qualitas", which in Latin means " quality».
The set of those tolerances that correspond to the same level of accuracy for all nominal sizes is called the qualification system.
The standard established 20 qualifications - 01, 0, 1, 2...18 . As the quality number increases, the tolerance increases, i.e., the accuracy decreases. Qualities from 01 to 5 are intended primarily for calibers. For landings, qualifications are provided from the 5th to the 12th.
| Numerical tolerance values | |||||||||||||||||||||
| Interval nominal sizes mm |
quality | ||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 01 | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | ||
| St. | Before | micron | mm | ||||||||||||||||||
| 3 | 0.3 | 0.5 | 0.8 | 1.2 | 2 | 3 | 4 | 6 | 10 | 14 | 25 | 40 | 60 | 0.10 | 0.14 | 0.25 | 0.40 | 0.60 | 1.00 | 1.40 | |
| 3 | 6 | 0.4 | 0.6 | 1 | 1.5 | 2.5 | 4 | 5 | 8 | 12 | 18 | 30 | 48 | 75 | 0.12 | 0.18 | 0.30 | 0.48 | 0.75 | 1.20 | 1.80 |
| 6 | 10 | 0.4 | 0.6 | 1 | 1.5 | 2.5 | 4 | 6 | 9 | 15 | 22 | 36 | 58 | 90 | 0.15 | 0.22 | 0.36 | 0.58 | 0.90 | 1.50 | 2.20 |
| 10 | 18 | 0.5 | 0.8 | 1.2 | 2 | 3 | 5 | 8 | 11 | 18 | 27 | 43 | 70 | 110 | 0.18 | 0.27 | 0.43 | 0.70 | 1.10 | 1.80 | 2.70 |
| 18 | 30 | 0.6 | 1 | 1.5 | 2.5 | 4 | 6 | 9 | 13 | 21 | 33 | 52 | 84 | 130 | 0.21 | 0.33 | 0.52 | 0.84 | 1.30 | 2.10 | 3.30 |
| 30 | 50 | 0.6 | 1 | 1.5 | 2.5 | 4 | 7 | 11 | 16 | 25 | 39 | 62 | 100 | 160 | 0.25 | 0.39 | 0.62 | 1.00 | 1.60 | 2.50 | 3.90 |
| 50 | 80 | 0.8 | 1.2 | 2 | 3 | 5 | 8 | 13 | 19 | 30 | 46 | 74 | 120 | 190 | 0.30 | 0.46 | 0.74 | 1.20 | 1.90 | 3.00 | 4.60 |
| 80 | 120 | 1 | 1.5 | 2.5 | 4 | 6 | 10 | 15 | 22 | 35 | 54 | 87 | 140 | 220 | 0.35 | 0.54 | 0.87 | 1.40 | 2.20 | 3.50 | 5.40 |
| 120 | 180 | 1.2 | 2 | 3.5 | 5 | 8 | 12 | 18 | 25 | 40 | 63 | 100 | 160 | 250 | 0.40 | 0.63 | 1.00 | 1.60 | 2.50 | 4.00 | 6.30 |
| 180 | 250 | 2 | 3 | 4.5 | 7 | 10 | 14 | 20 | 29 | 46 | 72 | 115 | 185 | 290 | 0.46 | 0.72 | 1.15 | 1.85 | 2.90 | 4.60 | 7.20 |
| 250 | 315 | 2.5 | 4 | 6 | 8 | 12 | 16 | 23 | 32 | 52 | 81 | 130 | 210 | 320 | 0.52 | 0.81 | 1.30 | 2.10 | 3.20 | 5.20 | 8.10 |
| 315 | 400 | 3 | 5 | 7 | 9 | 13 | 18 | 25 | 36 | 57 | 89 | 140 | 230 | 360 | 0.57 | 0.89 | 1.40 | 2.30 | 3.60 | 5.70 | 8.90 |
| 400 | 500 | 4 | 6 | 8 | 10 | 15 | 20 | 27 | 40 | 63 | 97 | 155 | 250 | 400 | 0.63 | 0.97 | 1.55 | 2.50 | 4.00 | 6.30 | 9.70 |
| 500 | 630 | 4.5 | 6 | 9 | 11 | 16 | 22 | 30 | 44 | 70 | 110 | 175 | 280 | 440 | 0.70 | 1.10 | 1.75 | 2.80 | 4.40 | 7.00 | 11.00 |
| 630 | 800 | 5 | 7 | 10 | 13 | 18 | 25 | 35 | 50 | 80 | 125 | 200 | 320 | 500 | 0.80 | 1.25 | 2.00 | 3.20 | 5.00 | 8.00 | 12.50 |
| 800 | 1000 | 5.5 | 8 | 11 | 15 | 21 | 29 | 40 | 56 | 90 | 140 | 230 | 360 | 560 | 0.90 | 1.40 | 2.30 | 3.60 | 5.60 | 9.00 | 14.00 |
| 1000 | 1250 | 6.5 | 9 | 13 | 18 | 24 | 34 | 46 | 66 | 105 | 165 | 260 | 420 | 660 | 1.05 | 1.65 | 2.60 | 4.20 | 6.60 | 10.50 | 16.50 |
| 1250 | 1600 | 8 | 11 | 15 | 21 | 29 | 40 | 54 | 78 | 125 | 195 | 310 | 500 | 780 | 1.25 | 1.95 | 3.10 | 5.00 | 7.80 | 12.50 | 19.50 |
| 1600 | 2000 | 9 | 13 | 18 | 25 | 35 | 48 | 65 | 92 | 150 | 230 | 370 | 600 | 920 | 1.50 | 2.30 | 3.70 | 6.00 | 9.20 | 15.00 | 23.00 |
| 2000 | 2500 | 11 | 15 | 22 | 30 | 41 | 57 | 77 | 110 | 175 | 280 | 440 | 700 | 1100 | 1.75 | 2.80 | 4.40 | 7.00 | 11.00 | 17.50 | 28.00 |
| 2500 | 3150 | 13 | 18 | 26 | 36 | 50 | 69 | 93 | 135 | 210 | 330 | 540 | 860 | 1350 | 2.10 | 3.30 | 5.40 | 8.60 | 13.50 | 21.00 | 33.00 |
The set of tolerances and landings, which is created on the basis of theoretical research and experimental surveys, as well as built on the basis practical experience, is called the system of tolerances and landings. Its main purpose is to select such options for tolerances and fits for typical joints of various parts of machines and equipment that are minimally necessary, but completely sufficient.
The basis for the standardization of measuring instruments and cutting tools make up exactly the most optimal gradations of tolerances and landings. In addition, thanks to them, the interchangeability of various parts of machines and equipment is achieved, as well as improving the quality of finished products.
For clearance unified system tolerances and landings tables are used. They indicate the reasonable values \u200b\u200bof the limit deviations for various nominal sizes.
InterchangeabilityWhen designing various machines and mechanisms, developers proceed from the fact that all parts must meet the requirements of repeatability, applicability and interchangeability, as well as be unified and comply with accepted standards. One of the most rational ways to fulfill all these conditions is to use at the design stage as much as possible a large number such constituent parts, the production of which has already been mastered by the industry. This allows, among other things, to significantly reduce development time and costs. At the same time, it is necessary to provide high precision interchangeable components, assemblies and parts in terms of their compliance with geometric parameters.
With the help of such technical method, as a modular layout, which is one of the ways of standardization, it is possible to effectively ensure the interchangeability of components, parts and assemblies. In addition, it greatly facilitates repairs, which greatly simplifies the work of the relevant personnel (especially in difficult conditions), and allows you to organize the supply of spare parts.
Contemporary industrial production focused mainly on the mass production of products. One of its prerequisites is the timely receipt of such components on the assembly line. finished products, which do not require additional fitting for their installation. In addition, interchangeability must be ensured that does not affect the functional and other characteristics of the finished product.
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