Description of staple caliber with specification. Why do you need a smooth plug gauge?
Caliber called a scaleless measuring instrument designed to control (check) the dimensions or shape and relative position of the surfaces of a part. Since the size of the part is limited by two maximum dimensions, to control them it is necessary to have two gauges, one of which controls the part according to its largest, and the other according to its smallest maximum dimensions. These calibers are called extreme. Unlike instruments and universal measuring instruments equipped with reading devices (scale), gauges do not determine the actual value of the controlled size, but only determine whether the controlled size is within the tolerance. When checking by limiting gauges, parts are sorted into three groups: suitable - with dimensions within the manufacturing tolerance range, final defects and correctable defects. Depending on the shape of the parts being controlled, gauges are divided into smooth, threaded, splined, etc. The most numerous are smooth gauges. They are divided into gauges for checking shafts (clips and rings) and gauges for checking holes (plugs).
Staples - gauges for checking shafts. Rings are rarely used, since they are less versatile and do not allow you to control parts on the machine, for example, the dimensions of the crankshaft journals. The staples have two sides: pass-through and non-pass-through. They differ not only in nominal dimensions, but also in appearance (the non-passing side of the bracket has chamfers on the measuring jaws).
The designs of staples are numerous and varied. The most common staples are single-sided, double-sided sheet, stamped and cast, and adjustable. Adjustable clamps can be adjusted to a different part size or restored to size as the gauge wears out. This increases the life of staples and reduces the cost of purchasing gauges. Adjustment of the size of the staple is achieved by moving one of the gauge inserts. Traffic jams are called gauges for checking holes.
The designs of plugs are quite diverse. They come in full and profiles, double-sided and single-sided, with inserts.
The gauges are marked with: the nominal size of the part, the conventional letter designation of the tolerance field of the part (the main deviation with the quality number), signs and digital values of the maximum deviations of the part (mm), the designation of the side of the gauge - PR (pass) and NOT (non-pass) and a trademark manufacturer's plant.
To control the wear of brackets (rings) and their sizes during the manufacturing process in grades from 1T6 to P77 with sizes up to 500 mm, three types of control gauges are provided:
K-PR- counter-caliber plug to control the size of the passage ETC new working bracket; K-NOT- counter-caliber plug to control the size of the impassable NOT new working bracket; K-I- counter-caliber plug for monitoring the wear of the pass-through bracket PR according to the greatest wear limit. If the caliber K-I passes through the controlled bracket, then it is worn beyond the established tolerance and must be removed.
Caliber tolerances(GOST 24853 - 81). For the manufacture of all types of gauges, tolerances are established, designated in Latin letters: H - for plugs (Hs - for gauges with spherical measuring surfaces); Н1 for staples and Нр - for counter-calibers.
In grades from 1T6 to 1T10 inclusive, the tolerances for staples are approximately 50% greater than the tolerances for plugs, which is explained by the greater complexity of manufacturing staples. In grades 1T11 and coarser, the tolerances for brackets are equal to the tolerances for plugs.
Pass-through gauges PR wear out during operation. The amount of wear of PR gauges is limited by the tolerance field of the part, and for parts with tolerances up to the 8th grade, the size of the gauge - plug (staple) is allowed to exceed this limit by the value V (VI). With nominal sizes over 180 mm, the tolerance field of the HE caliber and the wear limit of the PR pass-through gauge shifts inside the tolerance field of the part by an additional value b or b1 - the so-called “safety zone”. Shifting the tolerance fields of gauges and the wear limits of their pass sides inside the tolerance field of the part by the value z or z1 eliminates the possibility of distortion of the nature of the fits and guarantees obtaining the dimensions of suitable parts within the established tolerance fields.
GOST 24851-81
Group G28
INTERSTATE STANDARD
SMOOTH GAUGES FOR CYLINDRICAL HOLES AND SHAFTS
Plain gauges for cylindrical holes and shafts. Types
ISS 17.040.30
OKP 39 3100
Recording date 1982-01-01
INFORMATION DATA
1. DEVELOPED AND INTRODUCED by the Ministry of Machine Tool and Tool Industry of the USSR
2. APPROVED AND ENTERED INTO EFFECT by Resolution of the USSR State Committee for Standards dated June 23, 1981 N 3063
3. The standard fully complies with ST SEV 1919-79
4. INTRODUCED FOR THE FIRST TIME
5. REFERENCE REGULATIVE AND TECHNICAL DOCUMENTS
Application number |
|
Application |
|
Application |
6. EDITION with amendment No. 1, approved in September 1989 (IUS 12-89)
1. This standard applies to limiting smooth non-adjustable gauges for testing holes and shafts with nominal diameters from 1 to 500 mm, as well as control gauges for clamp gauges.
This standard fully complies with ST SEV 1919-79.
2. The numbers of caliber types, their designation and name must correspond to those indicated in the table.
Caliber type designation | Name of caliber type | Caliber type numbers according to ST SEV 1919-79 |
Shaft gauges and related control plug gauges |
||
Ring gauge smooth through | ||
Smooth pass-through clamp gauge | ||
Smooth no-go gauge | ||
Ring gauge smooth non-through | ||
Smooth control plug gauge for the new smooth passage clamp gauge | ||
Smooth control plug gauge for the new smooth non-go gauge. | ||
Smooth control plug gauge for monitoring the wear of the smooth pass-through clamp gauge | ||
Smooth control pass-through gauge for the new smooth pass-through clamp gauge | ||
Smooth control pass-through gauge for the new smooth non-through pass-through gauge | ||
Smooth control gauge for monitoring the wear of a smooth pass-through gauge-clip | ||
Hole gauges |
||
3. A schematic representation of the calibers is given in Appendix 1.
4. Rules for using calibers are given in Appendix 2.
SCHEMATIC REPRESENTATION OF CALIBERS
Designation and number of the caliber type | Caliber name and diagram |
PR (1), NOT (4) | Ring gauge smooth |
PR (2), NOT (3) | Smooth single-limit clamp gauge |
PR (2), NOT (3) | Smooth clamp gauge |
K-PR (5), K-NOT (6), PR (11) | Smooth bore plug gauge |
Smooth bore plug gauge |
|
K-I (7), NOT (12) | Smooth no-go plug gauge |
Smooth no-go plug gauge |
|
PR (11), NOT (12) | Smooth double-sided plug gauge |
K-PR (8), K-NOT (9), K-I (10) | Smooth control gauge, pass-through, non-pass-through |
APPENDIX 2 (mandatory). RULES FOR APPLICATION OF CALIBERS
APPENDIX 2
Mandatory
1. Shaft gauges and related control plug gauges
1.1. The smooth passage ring gauge (1) or the smooth passage clamp gauge (2) must pass along the shaft under the influence of its own weight or a certain force.
1.2. The smooth non-go-through clamp gauge (3) or the smooth non-go-through ring gauge (4) should not pass along the shaft, or, in extreme cases, bite.
1.3. Smooth control plug gauge (5) or smooth control passage gauge (8) for a smooth passage gauge (2).
The smooth passage gauge-bracket (2) must slide along the smooth passage gauge-plug (5) or the smooth control passage gauge (8) under the influence of its own weight or a certain force.
1.4. Smooth control pass-through plug gauge (6) or smooth pass-through control gauge (9) for a non-go through smooth clamp gauge (3).
The smooth non-go-through gauge-clip (3) must slide over the smooth control go-through gauge-plug (6) or over the smooth control through-gauge (9) under the influence of its own weight or a certain force.
1.5. Smooth control plug gauge (7) or smooth control gauge (10) to monitor the wear of the smooth passage clamp gauge (2).
The smooth passage gauge-bracket (2) should not pass over the smooth control plug gauge (7) or the smooth control gauge (10), or, in extreme cases, bite.
1.6. Instead of control gauges, for monitoring staple gauges with dimensions up to 180 mm, it is allowed to use universal measuring instruments, plane-parallel gauge blocks, and for all sizes of staple gauges - certified product samples.
It is recommended to designate the size of the block of plane-parallel gauge blocks and the certified sample of the product close to the smallest limit size of control gauges (5, 8 and 6, 9) and to the largest limit size of control gauges 7, 10.
2. Hole gauges
2.1. The smooth bore plug gauge (11) must pass freely through the hole under the influence of its own weight or a certain force.
2.2. The smooth non-go through plug gauge (12), as a rule, should not enter the hole under the influence of its own weight or a certain force, or in extreme cases, bite.
3. Caliber control rules
3.1. The caliber must be removed from use when its wear reaches the limit established in GOST 24853.
3.2. If disagreements arise in assessing the quality of a product between the manufacturer and the consumer, it is recommended:
3.2.1. When checking a hole or shaft during their manufacture, use new or slightly worn go-through gauges and non-go-through gauges with dimensions close to the smallest for a plug gauge and the largest for a bracket (ring) gauge.
3.2.2. When inspecting a hole or shaft by the manufacturer's inspectors and the customer's representative, use go-through gauges with dimensions close to the permissible wear limit, and no-go gauges with sizes close to the largest for the plug gauge and the smallest for the bracket (ring) gauge.
3.1, 3.2. (Changed edition, Amendment No. 1).
3.3. Checking the correctness of determining the dimensions of products should be carried out with gauges with dimensions close to the wear limit of a pass gauge and to the tolerance limit of a new non-go gauge (the smallest for a clamp (ring) gauge and the largest for a plug gauge).
The text of the document is verified according to:
official publication
Calibers. Part 1: Sat. GOST. -
M.: IPK Standards Publishing House, 2003
Calibers are scaleless measuring instruments designed to check the size, shape and relative position of the surfaces of parts.
Calipers are classified as one-dimensional instruments, since the measuring parts of gauges do not change during the measurement process. Calibers are divided into two groups:.
normal and extreme Normal calibers
are manufactured according to the nominal size of the part being tested and have a measuring part equal to the average permissible size of the part being measured. A normal gauge should fit into a part with a greater or lesser density. Limit calibers
have dimensions nominally equal to the maximum dimensions of the part being measured. One of the sides of the caliber corresponds to the largest, and the other to the smallest specified limit size. When measuring with limit gauges, the pass side must fit into the hole or fit onto the shaft, and the second side - the non-go side - should not fit into the hole or fit onto the shaft. The non-pass side of the gauge differs from the pass side by an annular groove on the handle or by a shorter length of the measuring part. The non-go side of the gauge is shortened because it usually does not fit into the hole being checked. Using limit gauges, it is determined whether the actual dimensions of parts are outside the established limits or not. Depending on the parts elements being checked
calibers are divided as follows:
1) to check holes;
2) for checking shafts;
3) to check threads;
4) for checking conical holes, etc. By purpose, calibers are divided into workers And.
reception rooms Working calibers
used in the manufacture of products. They are used to check parts on the job site. are intended for inspectors who use them to check parts at control points or in technical control departments (QC).
In accordance with OST 1201, 1219 and 1220, calibers have the following designations:
R-PR (or PR) - the through side of the working caliber;
R-NOT (or NOT) - non-pass side of the working caliber;
P-PR - pass side of the receiving caliber;
P-NOT - non-pass side of the receiving gauge.
For calibers the following markings are applied:
a) the nominal size of the product for which the gauge is intended;
b) maximum deviations of the product (fit, accuracy class);
c) purpose of the caliber (PR - passing side and NOT - non-passing side);
d) trademark of the manufacturer.
On one-sided two-limit calibers, the designations PR and NOT are not placed.
There are many and varied designs of gauges for testing cylindrical surfaces (shaft and hole).
![](https://i2.wp.com/delta-grup.ru/bibliot/18/5-75.jpg)
![](https://i0.wp.com/delta-grup.ru/bibliot/18/5-76.jpg)
Rice. 58. Normal calibers:
a - plug gauge, b - ring, c - bracket
In Fig. 58 shows normal calibers: ring, plug and staple.
Ring and staple check the diameter of the shaft, and cork- hole diameter. To measure shafts they are mainly used staples.
Rings allow you to more accurately check the shaft, since they cover its entire surface.
However, the rings are expensive to manufacture and therefore their use is limited. In addition, rings cannot be used to measure journals in the middle of shafts, as well as shafts fixed in the centers. Of the staples, the most common are limiting one-sided staples (Fig. 59).
Rice. 59.
Inspection of parts in mechanical engineering is carried out using universal measuring instruments, devices and limit gauges. Familiarization with the most common tools and devices will take place during practical and laboratory work, so we will consider in detail only the control of parts with maximum calibers.
Parts with a tolerance of 6 ... 18 qualifications are checked with maximum calibers most often in conditions of mass and large-scale production. Using limit gauges, it is not the absolute value of the size of a part that is determined, but its suitability, that is, whether or not the actual size of the part exceeds the established limit dimensions.
Thus, maximum caliber– a scale-free measuring instrument used to check the suitability of parts according to their maximum dimensions.
The set of limit gauges for testing smooth cylindrical parts includes:
Pass-through gauge (PR) to check the pass-through limit (maximum part material);
No-go gauge (NOT) to check the no-go limit (minimum part material).
The part is considered suitable if the pass-through gauge passes under the influence of gravity or approximately equal to it, and the non-go-through gauge does not pass along the controlled surface of the part. In this case, the actual size of the part is between the specified limit dimensions (Figure 3.1).
Figure 3.1 – Scheme for monitoring parts with maximum calibers
If the pass gauge does not pass, it is a correctable defect; if a non-passing caliber passes, the defect is irreparable. Marriage is an extraordinary phenomenon. During inspection, pass gauges, as a rule, pass, but non-go gauges do not pass. Therefore, pass-through gauges wear out, while non-go-through gauges practically do not wear out. For the same reason, there is no need to make no-go gauges with a large working surface length, consuming expensive tool material. And pass-through gauges, compared to non-go-through gauges, are made with a longer working surface to eliminate distortion and jamming during inspection and to ensure reliable guidance of the gauge along the surface being tested. When checking small sizes, the weight of the caliber may be insufficient for its free passage. For large sizes, on the contrary, they strive to limit the influence of the weight of the caliber on the quality of control by introducing elements into the design of the caliber to lighten its weight. The gauges must have the greatest rigidity with the least weight, which is especially important for large staples.
Classification of calibers
Smooth limit gauges differ in name, design and purpose.
By name, calibers are divided into:
− traffic jams.
By design, calibers are:
Rigid and adjustable;
Solid and composite;
Single-sided, double-sided and combined.
By purpose, calibers are divided into:
− workers;
− reception rooms;
− control.
Working calibers(R-PR, R-NOT) are designed to control parts during their manufacturing process. These calibers are used by workers and quality control inspectors of the manufacturer. In this case, inspectors use partially worn-out R-PR gauges and new R-HE gauges, the so-called receiving gauges.
Reception gauges are intended for inspection of parts by customer representatives. These calibers were officially in the OST system. They are not provided for in modern standards, but they can be introduced by enterprise standards. Receiving gauges are not specially manufactured, but are selected from working gauges (partially worn R-PR and new R-NE). This is done to insure against the occurrence of accidental correctable defects and to ensure that parts correctly accepted by working calibers are not rejected by the calibers of the inspector and the customer’s representative.
Control gauges(counter-gauges) are intended for installation on the size of adjustable calibers and control of non-adjustable gauges during their manufacture and operation. Counter gauges are intended only for staples, that is, they are used only in the manufacture of shafts. The use of counter gauges when processing holes is not economically feasible: working plug gauges are easier to control with instruments than to use counter gauges that are difficult to manufacture and expensive.
Consequently, counter-calibers are just plugs:
– K-PR – for bracket R-PR;
– K-NOT – for bracket R-NOT;
– K-I – for removing from service extremely worn R-PR brackets.
Despite the small tolerance of counter-calibers, they still distort the established tolerance fields for the manufacture and wear of working calibers, therefore, if possible, counter-calibers should not be used. It is advisable to replace them, especially in small-scale production, and even more so in single production, with gauge blocks or use universal measuring instruments. It is not recommended to check parts with a tolerance of 01...5 grades with gauges, since with small tolerances they introduce a significant measurement error, and the manufacture of gauges of such accuracy is difficult and time-consuming. In such cases, the parts are checked using universal measuring instruments and instruments.
To reduce the cost of calibers, they strive to increase their wear resistance through the use of hard alloys and the application of wear-resistant coatings on their working surfaces.
3.2 Caliber tolerances
Tolerances and deviations of gauge sizes are established by GOST 24853-81 “Smooth gauges for sizes up to 500 mm. Tolerances." The standard provides for the following tolerances and deviations of calibers:
– | approval for the manufacture of plug gauges for holes; | |
H 1 | – | approval for the manufacture of gauges for the shaft; |
Hp | – | approval for the manufacture of a control gauge for the staple; |
– | deviation of the middle of the tolerance field for the manufacture of P-PR plugs relative to the smallest maximum hole size; | |
– | deviation of the middle of the tolerance field for the manufacture of the R-PR bracket relative to the largest maximum shaft size; | |
– | permissible deviation of the size of a worn P-PR plug beyond the tolerance zone of the hole; | |
– | permissible deviation of the size of a worn R-PR bracket beyond the tolerance range of the shaft; | |
– | value for compensating for errors in calibration control of holes with dimensions greater than 180 mm; | |
– | value for compensating for control errors with shaft calibers with dimensions greater than 180 mm. |
3.3 Layout of caliber tolerance fields
GOST 24853-81 provides for eight layouts of caliber tolerance fields depending on the grades and nominal sizes of the parts being inspected. The most common are the schemes for holes (Figure 3.2 a) and shafts (Figure 3.2 b) of grades 6, 7 and 8 with nominal sizes over 180 mm.
The remaining diagrams are special cases of the indicated general schemes for the location of caliber tolerance fields. For R-PR calibers, in addition to the manufacturing allowance, a wear allowance is provided. In this case, the tolerance field of the caliber is shifted inside the tolerance field of the part, and the wear tolerance field extends beyond the tolerance field of the part. For parts of 9...17 grades (with large tolerances), the tolerance field for caliber wear is located inside the tolerance field of the part and is limited by its passing limit, i.e. Y = 0 and Y 1 = 0. With nominal sizes up to 180 mm, the error in checking parts with gauges is insignificant and therefore is not taken into account, i.e. And .
Figure 3.2 – Layout of gauge tolerance fields for holes (a) and shafts (b) of grades 6, 7 and 8 with nominal sizes over 180 mm
It should be noted that in diagrams the wear of R-PR calibers is more clearly and conveniently depicted not by a wear boundary, but by a wear tolerance field, by analogy with the manufacturing tolerance field, as shown in Figure 3.3.
Shifting the tolerance fields of gauges and the wear limits of their leading sides inside the tolerance field of the part eliminates the possibility of distortion of the nature of the fits and guarantees obtaining the dimensions of suitable parts within the established tolerances. This is completely impossible to achieve for precision parts (grades 6...8) due to fairly tight tolerances and the increased cost of manufacturing parts. The tolerance fields for wear of R-PR calibers for such parts go beyond the limits of the tested tolerance field. In this case, the tolerance of the part is slightly expanded, without causing a violation of interchangeability.
3.4 Calculation of the standard dimensions of calibers
The executive dimensions of calibers are the dimensions by which calibers are manufactured.
In the drawings of calibers, tolerances for their manufacture are specified “in the body” of the caliber, that is, both for the main hole and the main shaft. The nominal size of the caliber is taken to be the size corresponding to the largest amount of metal in the caliber. Thus, on the drawing of the staple, its smallest limit size with a positive deviation is indicated, for the plug (working and control) - the largest size with a negative deviation.
We present the basic calculation formulas for determining the sizes of calibers.
Largest size of new passage plug:
.
Smallest size of worn passage plug
Largest plug size
.
Smallest size for a new bracket to pass through
.
Largest size of worn pass-through bracket
Smallest no-go staple size
.
The largest sizes of control gauges:
;
;
.
Caliber sizes obtained by calculation are rounded in accordance with GOST 24853-81. A tabular method for calculating the executive dimensions of working calibers, which is simpler for practical use, is set out in the same standard.
Let's consider an example of calculating the executive dimensions of gauges for monitoring connection parts.
According to GOST 25347-82 and GOST 24853-81 we find the maximum deviations of the dimensions of parts and the necessary data for calculating the sizes of gauges:
EI = 0; ES =+ 30µm; ei = – 29µm; es = – 10µm;
H=H 1 = 5µm; H P = 2µm; Z = Z 1 = 4 µm;
Y=Y 1 = 3µm; a = a 1 = 0.
Let's build a diagram of the location of caliber tolerance fields (Figure 3.3).
Figure 3.3 – Scheme for calculating gauge sizes V
Working plug gauges for holes:
Standard dimensions of plug gauges:
;
;
.
Working gauges for the shaft:
Executive dimensions of calipers:
; ; .
Reference calibers:
Executive dimensions of control gauges:
K – PR = 59,987 –0,002 ; K – I = 59,994 –0,002 ; K – NOT = 59,972 –0,002 .
1 What is a smooth limit gauge?
2 What types of smooth gauges are used in production?
3 How do control gauges differ from working gauges?
4 Under what production conditions is caliber control used?
5 Under what production conditions is control using universal measuring instruments used?
4 Tolerances and fits
prismatic key connections
Keyed connections are usually designed to connect to the shafts of gears, pulleys, flywheels, couplings and other parts and serve to transmit torque. Due to the variety of designs, we will focus on considering only the most widely used connection in mechanical engineering with parallel keys, a schematic representation of which is shown in Figure 4.1 a.
Dimensions, tolerances, fits and maximum deviations of connections with parallel keys are regulated by GOST 23360-78. The standard establishes tolerance fields for the width of keys and keyways for loose, normal and tight connections. For the width of the grooves of the shaft and bushing, any combination of tolerance fields shown in Figure 4.1 b is allowed.
As mentioned earlier, the fits of the key joints are assigned to the shaft system. An example of a keyed connection between a shaft and a bushing is shown in Figure 4.2.
Figure 4.1 – Tolerance fields for keyed connections
Figure 4.2 – Example of indicating the landings of a keyed connection in the drawings
Control of the dimensions, symmetry of location and straightness of the keyways of the bushing and shaft is carried out with universal measuring instruments, smooth limit and special gauges.
Test questions and assignments
1 In what cases and for what are keyed connections used?
2 Are keyed connections used for transitional fits?
3 In what system are keyed joint fits prescribed?
4 How is the size of keyways controlled?
5 Tolerances and fits of rolling bearings
For rolling bearings, the connecting surfaces are the outer surface of the outer ring and the inner surface of the inner ring. The connecting surfaces of the bearings provide complete external interchangeability, which allows you to quickly mount them, as well as replace worn bearings with good assembly quality.
5.1 Accuracy classes of rolling bearings
The quality of bearings is determined by the precision of manufacturing of their parts and the accuracy of assembly. The main indicators of the accuracy of bearings and their parts are:
Dimensional accuracy of connecting surfaces;
The accuracy of the shape and location of the surfaces of the rings and the roughness of their surfaces;
Accuracy of the shape and size of rolling elements and the roughness of their surfaces;
Rotation accuracy, characterized by radial and axial runout of raceways and ring ends.
Depending on these accuracy indicators according to GOST 520-2011 “Rolling bearings. General Technical Conditions" establishes the following accuracy classes of bearings, indicated in order of increasing accuracy:
− normal, 6, 5, 4, T, 2 – for ball and roller radial and ball angular contact bearings;
− 0, normal, 6Х, 6, 5, 4, 2 – for tapered roller bearings;
− normal, 6, 5, 4, 2 – for thrust and angular contact bearings.
The most accurate is the second accuracy class. The bearing accuracy class is selected based on the requirements for rotational accuracy and operating conditions of the mechanism. For general-purpose mechanisms, bearings of accuracy class 0 are usually used. Bearings of higher accuracy classes are used at high speeds and high accuracy of shaft rotation, for example, for spindles of grinding machines, aircraft engines, instruments, etc. For gyroscopic and other precision instruments and mechanisms, class bearings are used accuracy 2.
The accuracy class is indicated by a dash before the symbol of the bearing series, for example, 6–205. For all bearings, except tapered ones, the accuracy class “normal” is indicated by the sign “0”.
Given the wide variety of bearing designs, we will limit ourselves to considering fits only for radial ball bearings.
5.2 Tolerances and fits of connections with rolling bearings
The fit of the outer ring of the bearing with the housing is carried out in the shaft system, the fit of the inner ring with the shaft is carried out in the hole system. The diameters of the outer and inner rings of the bearing are taken respectively as the diameters of the main shaft and the main hole with a certain reservation, which will be discussed below.
In most cases, particularly with a rotating shaft, the inner ring of the bearing is mounted stationary on the shaft. To do this, it is necessary to use either transitional fits or interference fits. However, the use of these and other landings is excluded for the following reasons:
The former require additional fastening (keys, etc.), which will complicate the design of the bearing and is unacceptable in terms of accuracy (uneven deformation of the ring during hardening due to stress concentrators) or is generally structurally unfeasible due to the insufficient thickness of the bearing ring;
The latter give an interference that is unacceptable due to the strength of the inner ring of the bearing.
The introduction of any special fits with low interference for rolling bearings is not economically feasible. Therefore, they do this: a standard tolerance field for a transitional fit is assigned to the shaft, and the tolerance field of the inner ring of the bearing is lowered symmetrically down relative to the zero line. Consequently, for the inner rings of bearings, the size tolerance is set to minus, and not to plus, as is customary for conventional main holes. This combination of tolerance fields ensures tightness that is permissible for the strength of the inner ring and guarantees the immobility of the connection.
Figure 5.1 – Example of landings of ball radial bearings
Thus, the main (upper) deviations of both connecting diameters of rolling bearings are assumed to be zero (Figure 5.1) and are designated by uppercase and lowercase letters L workers l, respectively for the inner and outer rings of the bearing.
The choice of bearing fit on the shaft and in the housing is made depending on the accuracy class of the bearing (Figure 5.1), the type of loading of the bearing rings, its operating mode, the magnitude and nature of the load, rotation speed and other factors.
Depending on the design and operating conditions of the product in which the bearings are mounted, the bearing rings may experience different types of loading: local, circulation and vibration (Figure 5.2).
Under local loading, the ring perceives a constant radial load (for example, the tension of the drive belt, the force of gravity of the structure) only in a limited area of the raceway and transfers it to the corresponding limited area of the seating surface of the shaft or housing (Figures 5.2 a and 5.2 b).
Under circulation loading, the ring absorbs the radial load sequentially around the entire circumference of the raceway and also transmits it sequentially to the entire seating surface of the shaft or housing (Figures 5.2 a and 5.2 b).
A) b) V) G)
Figure 5.2 – Types of loading of bearing rings
Under oscillatory loading, the ring perceives the resultant of two radial loads (one is constant in direction, and the other, smaller in magnitude, rotates) by a limited section of the raceway and transfers it to the corresponding limited section of the seating surface of the shaft or housing (Figures 5.2 c and 5.2 d). The resultant load in this case does not make a full revolution, but oscillates between points A and B.
Depending on the type of loading of the radial bearing rings, the following tolerance fields are established that form the fits (Table 5.1).
Table 5.1 – Tolerance fields of shafts and housing holes for installing radial bearings
When the shaft rotates, a fixed fit is assigned to the inner ring and a movable fit to the outer ring. With a stationary shaft it is the opposite. The bearing is mounted with a gap along the ring that experiences local loading. This eliminates ball jamming and allows the ring to gradually rotate along the seating surface under the influence of shocks and vibrations, which ensures uniform wear on the treadmill and extends bearing life.
The bearing is mounted with an interference fit on a ring experiencing circulation loading, which prevents the ring from slipping along the seating surface and eliminates the possibility of its abrasion and flaring.
The designation of bearing fits has its own characteristics. As was shown earlier, a special main deviation of the hole is established for bearings, which does not correspond to the main deviation according to GOST 25347-82. It is indicated by a capital letter L. For the purpose of unification, the main deviation of the outer ring of the bearing is indicated by a lowercase letter l. Considering that the use of a hole system for connecting the inner ring of the bearing with the shaft and a shaft system for connecting the outer ring with the housing is mandatory, it is customary to designate bearing ring landings in assembly drawings with one tolerance field.
In assembly drawings, the bearing fit is indicated by the tolerance field of the part mating with its corresponding ring, for example, along the outer ring, along the inner ring. If the accuracy class of the bearing is known, for example 6, then the tolerance fields for the connecting diameters of the bearing will have the following symbols: for the outer diameter - l6, internal diameter– L6, and the dimensions for the given example are respectively and In this case, fits along the connecting diameters of the bearing can be designated in the form of a traditional fraction: along the outer diameter – , along the inner diameter –
Test questions and assignments
1 What are the features of the purpose of landings of rolling bearings?
2 What types of loading of bearing rings exist?
3 How do fits depend on the type of loading of bearing rings?
4 How are the fits of rolling bearings indicated on the drawings?
Tolerances and landings
Related information.
CONTROL OF PARTS WITH SMOOTH GAUGES
To perform technical control operations, especially in mass and large-scale production, workers and inspectors of technical control departments (QC) widely use calibers.
Caliber– a control device that reproduces the geometric parameters of product elements, determined by specified limit lines or angular dimensions, and is in contact with product elements along surfaces, lines or points. Product element means
structurally completed part of the product. For example: shaft, hole, groove, protrusion, thread, etc.
Calibers– this is a special technological equipment designed to assess the suitability of parts and mechanical engineering products (tolerance control). Inspection by gauges has higher productivity than measuring the actual dimensions of parts using measuring instruments. However, designing and manufacturing calibers is cost effective in high volume and mass production.
Using gauges, parts are sorted into good and bad (rejects). Calibers do not determine the numerical value (actual size) of the controlled parameter, but only establish whether the product element is within the limits of the maximum dimensions. A distinction is made between correctable defects, when the shafts are made with oversized dimensions and the holes with undersized ones, and irreparable defects, when the shaft dimensions are underestimated and the hole dimensions are overestimated.
Gauge control leads to a certain tightening of the tolerance for the manufacture of a part compared to the table value.
Gauges are used to control smooth cylindrical surfaces, for conical, threaded, keyed and spline surfaces, as well as to control the location of surfaces.
There are normal and extreme calibers.
Normal caliber- a gauge that reproduces a given linear or angular size and shape of the surface of the controlled element of the product mating with it, i.e. They only have a pass-through side.
Normal gauges (templates, location gauges) are used to control parts with complex surface profiles. The suitability of a part is judged by the size of the gap between its contour and the normal gauge for the uniformity of clearance or under the probe.
Limit caliber– a gauge that reproduces the pass and fail limits of the geometric parameters of the product, i.e. these calibers have a pass ( ETC) and impassable ( NOT) sides. Limit gauges include smooth gauges for checking shafts and holes, thread gauges and others.
By purpose, calibers are divided into:
- working calibers, intended for checking the dimensions of parts by workers and quality control inspectors;
- acceptance gauges− usually these are worn-out working calibers (their dimensions are within the wear tolerance), they are used by customer representatives;
- control calibers(counter gauges) are used to check the dimensions of working and acceptance gauges and to set the size of the adjustable bracket
To control the outer (male) surfaces of shafts, clamp gauges are used, and to control the internal (female) surfaces of holes, plug gauges are used.
Calibers - staples can be adjustable or non-adjustable. Adjustable gauges allow adjustment to another size (due to a movable insert) or restoration of the size of the pass side as it wears out. Non-adjustable staples are used more widely because they have a rigid structure, are cheaper and easier to manufacture.
8.2. CALCULATION OF EXECUTIVE SIZES
SMOOTH CALIBERS
The performance size of a caliber is the size to which a new caliber is manufactured. Tolerances for the manufacture of the caliber are specified “in the body” of the caliber in the form of a one-sided deviation: positive for the staple and negative for the plug. Nominal sizes of pass gauges ETC and impassable NOT are the maximum dimensions of the part.
Nominal size of pass gauge ETC corresponds to the maximum material of the tested object, i.e. for a shaft - the largest limit size, and for a hole - the smallest limit size.
Nominal size of no-go gauge NOT corresponds to the minimum material of the object being tested, i.e. for a shaft - to the smallest limit size, and for a hole - to the largest limit size.
Tolerances for the manufacture and wear of smooth gauges are specified in GOST 24853 “Smooth gauges for sizes up to 500 mm. Tolerances." Conventional designations of tolerance fields have been adopted N − for traffic jams and N 1 − for staples. The caliber tolerance value depends on the nominal size of the part and the quality of the controlled size (Table 8. 1). The layout diagrams of the tolerance fields of plug gauges are shown in Fig. 8.1.
All pass-through gauges have tolerance fields ( H And N 1 ) are shifted inside the tolerance field of the part by the amount Z − for plug gauges and Z 1 − for clamp gauges. For nominal sizes over 180 mm, the tolerance field is a non-go-through gauge.
Table 8.1
Tolerances and deviations of smooth gauges and
counter-calibers, microns (according to GOST 24853-81)
Quality | Designation | Intervals of nominal values of controlled sizes, mm | Tolerances of cork shape | |||||||||
St. 3 to 6 | 6… | 10… | 18… | 30… | 50… | 80… | 120… | 180… | 250… | |||
Z | 1,5 | 1,5 | 2,5 | 2,5 | IT1 | |||||||
Y | 1,5 | 1,5 | ||||||||||
a,a 1 | ||||||||||||
Z 1 | 2,5 | 3,5 | ||||||||||
Y 1 | 1,5 | 1,5 | ||||||||||
H | 1,5 | 1,5 | 2,5 | 2,5 | ||||||||
H 1 | 2,5 | 2,5 | ||||||||||
Hp | 1,2 | 1,5 | 1,5 | 2,5 | 3,5 | 4,5 | ||||||
Z,Z 1 | 2,5 | 3,5 | IT2 | |||||||||
Y,Y 1 | 1,5 | 1,5 | ||||||||||
a,a 1 | ||||||||||||
H,H 1 | 2,5 | 2,5 | ||||||||||
Hp | 1,2 | 1,5 | 1,5 | 2,5 | 3,5 | 4,5 | ||||||
Z,Z 1 | IT2 | |||||||||||
Y,Y 1 | ||||||||||||
a,a 1 | ||||||||||||
H | 2,5 | 2,5 | ||||||||||
H 1 | ||||||||||||
Hp | 1,5 | 1,5 | 2,5 | |||||||||
9* | Z,Z 1 | IT2 | ||||||||||
a,a 1 | ||||||||||||
H | 2,5 | 2,5 | ||||||||||
H 1 | ||||||||||||
Hp | 1,5 | 1,5 | 2,5 | 2,5 | ||||||||
10* | Z,Z 1 | IT2 | ||||||||||
a,a 1 | ||||||||||||
H | 2,5 | 2,5 | ||||||||||
H 1 | ||||||||||||
Hp | 1,5 | 1,5 | 2,5 | 2,5 | ||||||||
11* | Z,Z 1 | IT4 | ||||||||||
a,a 1 | ||||||||||||
H,H 1 | ||||||||||||
Hp | 1,5 | 1,5 | 2,5 | 2,5 | ||||||||
12* | Z,Z 1 | IT4 | ||||||||||
a,a 1 | ||||||||||||
H,H 1 | ||||||||||||
Hp | 1,5 | 1,5 | 2,5 | 2,5 |
Note: For grades marked (*) for all size ranges Y=Y 1 =0.
Rice. 8.1. Layout of tolerance fields for plug gauges for hole inspection:
A− up to 180 mm, grades 6…8 ; b−over 180 mm, grades 6...8;
V− up to 180 mm, grades 9…17; G−over 180 mm, grades 9…17
Rice. 8..3. Schemes of location of tolerance fields of staple gauges
for monitoring quality shafts 9…17: A− up to 180 mm; b−over 180 mm
also shifts inside the tolerance zone of the part by the amount a− for traffic jams and a 1− for staples. For sizes up to 180 mm a = a 1 = 0.
For pass gauges, a wear tolerance is provided, which reflects the average probable wear of the gauge. For calibers up to grade 8, the wear tolerance goes beyond the tolerance range of the part by the amount Y − for traffic jams and Y 1 − for staples. For calibers of coarser grades (9...17), wear is limited to the pass limit, i.e. Y = Y 1 =0 . Operation of the caliber is possible within the wear limit. These calibers are used by customer representatives and are called acceptance gauges.
When using clamp gauges, their suitability is monitored using counter gauges that are shaped like the shaft. Counter-calibers have manufacturing approvals HP , which are located symmetrically relative to the middle of the tolerance fields of the calibers for manufacturing and the wear limit. The layout of the tolerance fields of the staple gauges is shown in Fig. 8..2 and 8.3). Counter-calibers are made in the form of washers in a set of 3 pieces, since they check the through side of the working caliber ( K-PR), wear on the pass side (K-I) and the non-passable side ( K-NOT).
It is advisable to produce control gauges only at specialized enterprises that produce staples in large quantities. In other cases, the control of staples is performed using blocks of gauge blocks.
Executive dimensions of calibers according to the corresponding diagram
The locations of tolerance fields are calculated using the formulas in Table. 8.2.
Table 8. 2
Formulas for calculation
maximum and standard sizes of calibers
up to 180 mm | over 180 mm | |
Traffic jams | (Fig.8.1, A;8.1,V = (D m i n +Z+H/ 2) PR min = (D m i n +Z−H/ 2) PR from = (D m i n − Y) NOT max = (D m a x +H/ 2) HE min = (D m a x − H/ 2) executive dimensions ( d) 1 PR = (D min +Z+H/ 2) - H NOT = (D max +H/ 2) - H | (Fig. 8.1, b;8.1,G) maximum dimensions PR max = (D m i n +Z+H/ 2) PR m i n = (D m i n + Z−H/ 2) PR from = (D m i n − Y+ a ) NOT max = (D max −a +H/ 2) N E m i n = (D max−a− H/ 2) executive dimensions ( d) 1 PR = (D m i n +Z+H/ 2) - H NOT = (D max −a +H/ 2) - H |
Staples | (Fig.8.2, A;8.3,A) maximum dimensions PR max = (d max - Z 1 +H 1 /2) PR m i n = (d max - Z 1 -H 1 /2) PR from = (d max + Y 1 ) NOT max = (d m i n +H 1 /2) NOTEmin = (d m i n − H 1 /2) executive dimensions ( D) 1 PR = (d max − Z 1 −H 1 /2) + H 1 NOT = (d m i n –H 1 /2) + H 1 | (Fig. 8.2, b;8.3,b) maximum dimensions PR max = (d max − Z 1 + H 1 /2) PR m i n = (d max − Z 1 −H 1 /2) PR from = (d max + Y 1 −a 1 ) NOT max = (d m i n + a 1 +H 1 /2) N E m i n = (d m i n + a 1 − H 1 /2) executive dimensions ( D) 1 PR = (d max − Z 1−H 1 /2) + H 1 NOT = (d m i n + a 1 − H 1 /2) + H 1 |
Counter calibers | (Fig.8.2, A;8.3,A) executive dimensions ( d) K-I =(d max +Y 1 +H R/2) - N r K-PR = (d max – Z 1 + H R/2) - N r K-NOT = (d m i n + H R / 2) - N r | (Fig. 8.2, b;8.3,b) executive dimensions ( d) K-I = (d max +Y 1 −a 1 +H R / 2) - N r K-PR = (d max – Z 1 +H R / 2)- N r K-NOT = (d m i n + a 1 +H R / 2) - N r |
Note: As-built dimensions in Fig. 2.1….2.8.
The standard dimensions of calibers should be rounded: for products of 6...14 qualifications and all counter-calibers - up to 0.5 µm in the direction of reducing the production tolerance, the tolerance value of the caliber and counter-caliber is maintained; for products of 15...17 quality - round to 1 micron.