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The control of parts in mechanical engineering is carried out by universal measuring tools, 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 limit gauges.
Parts with a tolerance of 6 ... 18 qualifications are checked with limiting calibers most often in conditions of mass and large-scale production. With the help of limit gauges, it is not the absolute value of the size of the part that is determined, but its suitability, that is, the actual size of the part goes or does not go beyond the established limit dimensions.
Thus limit caliber- a scaleless measuring tool used to check the suitability of parts according to the limiting dimensions.
The set of limit gauges for testing smooth cylindrical parts includes:
Passing gauge (PR) for checking the passage limit (maximum part material);
No-go gauge (NOT) for checking the no-go limit (minimum part material).
The part is considered valid if the through-going gauge passes under the action of gravity or approximately equal to it, and the non-going gauge does not pass through the controlled surface of the part. In this case, the actual size of the part is between the specified limit sizes (Figure 3.1).
Figure 3.1 - Scheme of control of parts by limit gauges
If the passing gauge does not pass, a reparable marriage; if the impassable caliber passes, the marriage is irreparable. Marriage is an extraordinary phenomenon. When inspected, passing gauges, as a rule, pass, but non-passable gauges do not. Therefore, pass-through calibers wear out, and non-pass-through ones practically do not wear out. For the same reason, there is no need to make non-going calibers with a long working surface, consuming expensive tool material. And pass-through gauges, in comparison with non-pass-through gauges, are made with a longer working surface length in order to prevent distortion and jamming during testing and to ensure reliable gauge guidance along the surface being checked. When controlling small dimensions, the weight of the caliber may not be sufficient for its free passage. For large sizes, on the contrary, they try to limit the influence of the weight of the gauge on the quality of control by introducing elements to lighten its weight into the design of the gauge. Gauges should have the greatest rigidity with the least weight, which is especially important for large staples.
Caliber classification
Smooth limit gauges differ in name, design and purpose.
By name, calibers are divided into:
- traffic jams.
By design, calibers are:
Rigid and adjustable;
Whole 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 in the process of their manufacture. These calibers are used by workers and inspectors of the quality control department of the manufacturer. At the same time, controllers use partially worn-out R-PR calibers and new R-NE calibers, the so-called receiving calibers.
Receiving calibers designed to check 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 calibers are not specially made, but are selected from working calibers (partially worn R-PR and new R-NE). This is done to insure against the appearance of an accidental correctable marriage and to ensure that the parts correctly accepted by the working gauges are not rejected by the gauges of the controller and the customer's representative.
Control gauges(counter-gauges) are designed to be set on the size of adjustable calibers-brackets and control unregulated calibers-brackets in the process of their manufacture and operation. Gauges are only for staples, that is, they are used only in the manufacture of shafts. The use of counter gauges in the processing of holes is not economically feasible: working plug gauges are easier to control with instruments than using difficult-to-manufacture and expensive counter-gauges-brackets.
Therefore, countercalibers are only corks:
- K-PR - for the bracket R-PR;
- K-NOT - for the R-NOT bracket;
- K-I - for the removal from operation of extremely worn-out brackets R-PR.
Despite the small tolerance of counter gauges, they still distort the established tolerance fields for the manufacture and wear of working gauges, so counter gauges should not be used if possible. It is advisable to replace them, especially in small-scale production, and even more so in a single one, with gauge length measures or use universal measuring instruments. Parts with a tolerance of 01 ... 5 qualifications are not recommended to be checked with calibers, since with small tolerances they introduce a significant measurement error, and the manufacture of calibers of such accuracy is difficult and time-consuming. In such cases, the parts are checked with universal measuring instruments and devices.
To reduce the cost of calibers, they seek to increase their wear resistance through the use of hard alloys and the application of wear-resistant coatings on their working surfaces.
3.2 Gauge tolerances
Tolerances and deviations in gauge sizes are established by GOST 24853-81 “Smooth gauges for sizes up to 500 mm. Tolerances". The standard provides for the following caliber tolerances and deviations:
| – | approval for the manufacture of plug gauges for the hole; | |
| H 1 | – | approval for the manufacture of gauges-brackets for the shaft; |
| Hp | – | approval for the manufacture of a control gauge for the bracket; |
| – | deviation of the middle of the tolerance field for the manufacture of cork R-PR relative to the smallest limit hole size; | |
| – | deviation of the middle of the tolerance field for the manufacture of the R-PR bracket relative to the largest limit size of the shaft; | |
| – | permissible output of the size of the worn plug R-PR beyond the tolerance field of the hole; | |
| – | permissible output of the size of the worn bracket R-PR beyond the tolerance field of the shaft; | |
| – | value for compensating the error of control by gauges of holes with dimensions over 180 mm; | |
| – | value for compensating the error of control by calibers of shafts with dimensions over 180 mm. |
3.3 Schemes for the location of tolerance fields for calibers
GOST 24853-81 provides eight schemes for the location of caliber tolerance fields depending on the qualifications and nominal dimensions of the parts being checked. The most common are 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 schemes are special cases of the indicated general schemes location of caliber tolerance fields. For calibers R-PR, in addition to manufacturing tolerance, a tolerance for their wear 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 goes beyond the tolerance field of the part. For details of 9...17 qualifications (with large tolerances), the wear tolerance field of the caliber is located inside the tolerance field of the part and is limited by its passage limit, i.e. Y \u003d 0 and Y 1 \u003d 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 tolerance fields for gauges for holes (a) and shafts (b) of grades 6, 7 and 8 with nominal sizes over 180 mm
It should be noted that in the diagrams, the wear of R-PR calibers is more clearly and more conveniently depicted not by the wear boundary, but by the wear tolerance field, by analogy with the manufacturing tolerance field, as shown in Figure 3.3.
The shift of the tolerance fields of calibers and the wear limits of their passing sides inside the tolerance field of the part eliminates the possibility of distorting the nature of the landings and ensures that the dimensions of suitable parts are obtained within the established tolerances. This is completely impossible to achieve for precision parts (qualities 6...8) due to rather tight tolerances and an increase in the cost of manufacturing parts. Tolerance fields for wear of calibers R-PR for such parts go beyond the checked tolerance field. In this case, the tolerance of the part is somewhat expanded without causing a violation of interchangeability.
3.4 Calculation of the executive dimensions of calibers
The executive dimensions of the calibers are the dimensions by which the calibers are made.
In the drawings of gauges, the tolerances for their manufacture are set “into the body” of the gauge, that is, both for the main hole and the main shaft. The size corresponding to the largest amount of metal in the caliber is taken as the nominal size of the caliber. Thus, in the drawing of the bracket, its smallest limit size with a positive deviation is affixed, for the plug (working and control) - the largest size with a negative deviation.
Here are the basic calculation formulas for determining the dimensions of calibers.
The largest size of the new plug:
.
The smallest size of a worn plug
Largest plug size
.
The smallest size of the through new staple
.
The largest size of the worn shackle
Smallest non-going staple
.
Largest dimensions control gauges:
; 
;
.
Caliber sizes obtained by calculation are rounded in accordance with GOST 24853-81. Tabular method for calculating the executive dimensions of working calibers, easier for practical application set out in the same standard.
Consider an example of calculating the executive dimensions of gauges to control the details of the connection.
According to GOST 25347-82 and GOST 24853-81, we find the maximum deviations in the dimensions of parts and the necessary data for calculating the dimensions of calibers:
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 the caliber tolerance fields (Figure 3.3).
Figure 3.3 - Scheme for calculating the dimensions of the caliber in
Working plug gauges for the hole:
Executive dimensions of plug gauges:
; 
; 
.
Working calibers-brackets for the shaft:
Executive dimensions of gauges-brackets:
; 
; .
Control gauges:
Executive dimensions of control gauges:
K - PR \u003d 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 What is the difference between reference gauges and working gauges?
4 Under what conditions of production is caliber control applied?
5 Under what production conditions is control by universal measuring instruments used?
4 Tolerances and fits
prismatic key connections
Keyed connections are intended, as a rule, for connection with shafts of gears, pulleys, flywheels, couplings and other parts and are used to transmit torque. Due to the variety of designs, we will focus only on the most widely used connection with feather keys in mechanical engineering, a schematic representation of which is shown in Figure 4.1 a.
Dimensions, tolerances, fits and limit deviations of connections with parallel keys are regulated by GOST 23360-78. The standard establishes tolerance fields for the width of the key and keyways for free, normal and tight connections. For the width of the grooves of the shaft and bushing, any combination of the tolerance fields shown in Figure 4.1 b is allowed.
As mentioned earlier, keyway fits are assigned in the shaft system. An example of a keyed connection of a shaft with a bushing is shown in Figure 4.2.
Figure 4.1 - Tolerance fields for keyed connections
Figure 4.2 - An example of specifying keyway landings in the drawings
The control of dimensions, symmetry of location and straightness of the keyways of the bushing and shaft is carried out by universal measuring instruments, smooth limit and special gauges.
Control questions and tasks
1 In what cases and for what are keyed connections used?
2 Are keyed connections used for transitional fits?
3 In which system are keyed landings assigned?
4 How is keyway sizing controlled?
5 Tolerances and fits of rolling bearings
For rolling bearings, the connecting surfaces are the outer surface of the outer and the inner surface of the inner rings. 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 accuracy of the manufacture 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;
The accuracy of the shape and size of the rolling elements and the roughness of their surfaces;
Rotational accuracy, characterized by the radial and axial runout of the raceways and the ends of the rings.
Depending on these accuracy indicators according to GOST 520-2011 “Rolling bearings. General Specifications” the following accuracy classes of bearings are established, indicated in order of increasing accuracy:
- normal, 6, 5, 4, T, 2 - for ball and roller radial and ball angular contact bearings;
- 0, normal, 6X, 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 class of accuracy. The accuracy class of the bearing is selected based on the requirements for rotational accuracy and the operating conditions of the mechanism. For mechanisms general purpose Usually, bearings of accuracy class 0 are 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, bearings of accuracy class 2 are used.
The accuracy class is indicated with a dash before the designation of the bearing series, for example, 6–205. For all bearings, except for tapered bearings, the accuracy class "normal" is indicated by the sign "0".
Considering the wide variety of bearing designs, we restrict ourselves to consideration of fits only for deep groove ball bearings.
5.2 Tolerances and fits of joints with rolling bearings
The landings of the outer ring of the bearing with the housing are carried out in the shaft system, the landings of the inner ring with the shaft - in the hole system. The diameters of the outer and inner rings of the bearing are taken respectively for the diameters of the main shaft and the main hole with a certain reservation, which will be discussed later.
In most cases, in particular when the shaft is rotating, the bearing inner ring is fixedly mounted on the shaft. To do this, it is necessary to apply either transitional landings or interference landings. However, the use of those and other landings is excluded for the following reasons:
The former require additional fastening (keys, etc.), which complicates 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 in terms of 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 proceed as follows: a standard tolerance field for transitional fit is assigned to the shaft, and the tolerance field of the inner ring of the bearing falls 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 bores. This combination of tolerance fields provides tightness allowable by the strength of the inner ring, and guarantees the immobility of the connection.
Figure 5.1 - An example of landings of deep groove ball bearings
Thus, the main (upper) deviations of both connecting diameters of rolling bearings are taken equal to zero (Figure 5.1) and are indicated by uppercase and lowercase letters L and 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 mode of operation, 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 can experience different types of loading: local, circulation and oscillatory (Figure 5.2).
Under local loading, the ring perceives a constant radial load (for example, the tension of the drive belt, the gravity of the structure) only by a limited section of the raceway and transfers it to the corresponding limited section of the shaft or housing seating surface (Figures 5.2 a and 5.2 b).
Under circulating loading, the ring perceives the radial load sequentially over the entire circumference of the raceway and also transfers it sequentially to the entire seating surface of the shaft or housing (Figures 5.2 a and 5.2 b).
a) b) in) 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 is 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 turn, but oscillates between points A and B.
Depending on the type of loading of the rings of radial bearings, the following tolerance fields are established, forming landings (table 5.1).
Table 5.1 - Tolerance fields of shafts and housing holes for installing radial bearings
With a rotating shaft, a fixed fit is assigned to the inner ring, and a movable fit to the outer ring. With a stationary shaft, the opposite is true. The bearing is mounted with clearance on the ring that experiences local loading. This eliminates ball jamming and allows the ring to gradually rotate on the seating surface due to shocks and vibrations, which ensures uniform wear of the treadmill and extends bearing life.
The bearing is mounted on an interference fit along the ring, which experiences circulation loading, which eliminates the slippage of the ring along the seating surface and eliminates the possibility of its abrasion and flaring.
The designation of bearing fits has its own characteristics. As shown earlier, for bearings, a special main hole deviation is established, which does not correspond to the main deviation according to GOST 25347-82. It is denoted 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. Given that the use of a hole system for connecting the inner ring of the bearing to the shaft and a shaft system for connecting the outer ring to the housing is mandatory, it is customary to designate the fit of the bearing rings on the assembly drawings with one tolerance field.
On assembly drawings, the fit of the bearing 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 of the connecting diameters of the bearing will have the following symbols: for the outer diameter - l6, inner diameter - L6, and the dimensions for the given example, respectively, and In this case, the fit on the connecting diameters of the bearing can be denoted in the form of a traditional fraction: according to the outer diameter - , according to the inner diameter -
Control questions and tasks
1 What are the features of the appointment of rolling bearings?
2 What types of loading are there for bearing rings?
3 How do landings depend on the type of loading of bearing rings?
4 How are rolling bearing fits shown on drawings?
Tolerances and landings
Similar information.
caliber called a scaleless measuring tool designed to control (check) the size or shape and relative position part surfaces. Since the size of the part is limited by two limit sizes, for their control it is necessary to have two calibers, one of which controls the part according to its largest, and the other according to the smallest limit sizes. Such calibers are called limiting. Unlike devices 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 tolerance. When controlling by limiting calibers, parts are sorted into three groups: suitable - with dimensions lying in the manufacturing tolerance field, final marriage and correctable marriage. Depending on the shape of the controlled parts, the calibers are divided into smooth, threaded, slotted, etc. The most numerous are smooth calibers. They are divided into gauges for checking shafts (brackets and rings) and gauges for checking holes (plugs).
Staples - Gauges for shaft control. Rings are rarely used, as they are less versatile and do not allow you to control details on the machine, for example, the dimensions of the crankshaft journals. Staples have two sides: through passage and impassable. They differ not only in nominal dimensions, but also appearance(the non-going side of the clamp has chamfers on the measuring jaws).
The designs of the brackets are numerous and varied. The most common brackets are single-sided, double-sided sheet, stamped and cast, as well as adjustable. Adjustable calipers can be readjusted to a different part size or resized as the caliber wears. This increases staple life and reduces gauge purchase costs. Adjustment of the size of the bracket is achieved by moving one of the caliber inserts. traffic jams called gauges for controlling holes.
The designs of plugs are quite diverse. They are full and profiles, double-sided and single-sided, with inserts.
Gauges are marked: the nominal size of the part, the symbolic 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 (passing through) and NOT (not passing) and a trademark factory - the manufacturer.
To control the wear of staples (rings) and their dimensions 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-gauge-plug to control the size of the passage ETC new working bracket; K-NOT- counter-caliber stopper to control the size of impassable NOT new working bracket; K-I- a counter-caliber stopper for monitoring the wear of the PR staple through the highest wear limit. If the caliber K-I passes through the controlled bracket, then it is worn out beyond the established tolerance and is subject to withdrawal.
Caliber tolerances(GOST 24853 - 81). Tolerances are established for the manufacture of all types of gauges, denoted by Latin letters: H - for plugs (Hs - for gauges with spherical measuring surfaces); H1 for staples and H p - for countercalibers.
In grades from 1T6 to 1T10 inclusive, tolerances for staples are approximately 50% higher than tolerances for plugs, which is explained by the greater complexity of manufacturing staples. In qualifications 1T11 and coarser, the tolerances for staples are equal to those for plugs.
Goal 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, it is allowed to go beyond this limit by the value of V (VI). With nominal sizes over 180 mm, the tolerance field of the HE caliber and the wear limit of the PR pass gauge are shifted inside the tolerance field of the part by an additional value b or b1 - the so-called "safety zone". The shift of the tolerance fields of calibers and the wear limits of their passing sides inside the tolerance field of the part by the value of z or z1 eliminates the possibility of distorting the nature of the landings and ensures that the dimensions of suitable parts are obtained within the established tolerance fields.
Smooth plug gauge is a device for controlling the dimensions of cylindrical holes, used in serial, large-scale and mass production. When checking, the part is considered fit if the cork passes sideways and does not pass through the inspected hole with an impassable edge. The force applied to the gauge should be approximately proportional to its mass.
A special means of controlling one or more dimensions, as well as the shape and relative position of the machined surfaces, is called a caliber. Their main difference from universal measuring instruments is that gauges do not have a scale, as they are designed to control one parameter or their complex. For example, using a vernier caliper or micrometer, you can measure the actual diameter of the shaft and compare with that indicated on the drawing. This is exactly what is done with a single or small-scale production.
But in the circumstances of serial and mass production, this is not economically feasible, because when measuring by universal means, when accuracy of the order of hundredths and thousandths of a millimeter is required, the results of control depend on the qualifications of the worker. High skill implies an appropriate salary, the time spent on the control process increases. These factors increase the cost of production.
Advantages of calibers:
- ease of use allows the use of low-skilled workers and supervisors;
- speed of control;
- Possibility to check several parameters at the same time.
Flaws:
- limited applicability;
- the inability to determine the numerical deviations of the dimensions.
The introduction of automation and computers is gradually reducing the use of these controls in mechanical engineering.
Types of devices
There are the following types of calibers:
They are a rod, at both ends of which there are cylindrical elements. One of them has the largest maximum hole size and is called a non-through plug (NOT), and the second is the smallest and is called a through passage (PR). The dead plug is noticeably shorter than the straight plug, thanks to which the worker or inspector quickly and correctly determines the suitability of the parts.
Smooth plug gauges are made in composite, handles are steel or plastic, in which inserts with tapered shanks or cylindrical nozzles are attached. To check holes in the range from 2 to 50 mm, tapered shanks are made, and for holes in the range of 30-100 mm, cylindrical nozzles are made. If the insert is only on one side of the handle, then such plug gauges are called one-sided.
They are used to control the diameters of the shafts, by design they are single-sided and double-sided. just as in the case of plugs, the PR bracket must pass, and the NOT bracket must not pass along the shaft. Otherwise, the shaft is considered unusable, and the marriage will be correctable only if it is necessary to remove excess metal to achieve the desired result.
When using clamps, under no circumstances should they be forced onto the shaft, as the clamp may “open up” and increase the distance between the measuring surfaces due to the compliance due to its design. To prevent this, you should put the bracket on a horizontally located shaft only under the influence of its own weight. In this case, the shaft is also rotated, which at the same time allows you to control deviations from the round profile in the cross section.
There are brackets for checking only one size (they are called rigid) and adjustable, which allow you to control a certain range of shaft diameters. Adjustable parts are made of hard alloys, which contributes to a significant increase in their service life.
These are sets of steel plates with a thickness of 0.02 to 1 mm and a length of 100 or 200 mm. They are used to control the gap between surfaces when assembling various mechanisms. In this case, one or more probes in a set are inserted into the gap in order to select the desired value.
When using probes, it is important to follow certain rules:
They are used to inspect conical surfaces, such as tool cones. With the help of a ring gauge, the suitability of the outer surfaces is checked, and the suitability of the inner surfaces is checked with a stopper. A part is considered good if its end is located in the zone between the risks or between the planes of the ledge. This distance is equal to the tolerance.
Gauges for checking the location of surfaces
Can be of various designs . They control:
The measuring elements of this type of gauges are arranged in such a way as to reproduce the configuration of the surfaces of the mating parts.
It is used for a comprehensive check of the average diameter, profile angle, as well as the largest internal diameter of an external thread or the smallest external diameter of an internal thread. With the help of these devices, metric, inch, trapezoidal, thrust and round threads with a diameter of 1 to 600 mm are checked.
The control set consists of working pass-through (PR) and non-pass-through (NOT) calibers, as well as from the control ones, which serve to check the working gauges-rings and plugs.
Through-going gauges shall be freely screwed into controlled threads, while non-going gauges shall not be screwed into it. It is allowed to screw on non-going calibers up to 2 turns, while the number of revolutions is determined when unscrewing the caliber and the controlled product. If the thread of the part being checked is short (less than 3 turns), then screwing on a non-going gauge is not allowed.
The PR thread gauge has a length of about 80% of the make-up length, that is, the length of contact between the bolt and nut threads, measured along their axis.
An impassable one has a length of at least 3 turns.
Requirements for manufacturing and operation
All calibers, regardless of their purpose and type, are subject to the following conditions:
Since calibers are an expensive and responsible tool, it is recommended to strictly follow certain rules when working with them:
- in no case apply force to the caliber or subject it to blows;
- the controlled surfaces must be clean, dry and free from burrs;
- when checking a part, it is forbidden to rotate it;
- it is impossible to carry out control of hot or warm products, as this changes their dimensions and calibers wear out faster;
- Strictly observe the deadlines for control checks.
During storage, the working surfaces of the gauges should not come into contact with metal objects.
Inspection of smooth cylindrical products such as shafts and bushings in mass and large-scale production is carried out using limit gauges (for products with dimensions from 1 to 360 mm).
Caliber intended to determine the suitability of parts with a tolerance from IT6 ... IT17.
Calibers check the dimensions of smooth cylindrical, conical, threaded and splined parts, the depths and heights of the protrusions, as well as the location of the surfaces and other parameters.
Clamp gauges are used to control the shafts, and plug gauges are used for holes.
Using gauges, it is impossible to determine the actual size of the part. With their help, it is found out whether the checked size goes beyond the upper or lower limit, or is between them.
For control use gauge set: passing (PR) and impassable (NOT).
By appointment calibers are divided:
- workers - are used by inspectors or workers in the control of parts in the process of their manufacture ( PR and NOT).
- control – in the control of working calibers in the process of their manufacture ( K-PR and K-NOT), and operation ( K-I wear). Made only for staples in the form of rings. They are not made for plugs (complex configuration, high accuracy). K-I - control the wear limit of the pass caliber.
Rules for the use of calibers
Detail considered fit, if the passing gauge (going side of the gauge) passes under the action of its own weight or a force approximately equal to it, and the non-going gauge does not pass through the controlled surface of the part.
If the PR caliber does not pass - a fixable marriage; DOES NOT pass - an incorrigible marriage.
Caliber designs
Plug gauges
Gauges-staples
Rigid and adjustable braces are used. Adjustable brackets can be adjusted to different sizes (up to 330mm), which allows you to compensate for wear and use one bracket to control sizes that lie in a certain interval. Used to control sizes 8 quality and coarser. Less accurate and less reliable than rigid ones.
PARTS CONTROL WITH SMOOTH GAUGE
To perform technical control operations, especially in mass and large-scale production, workers and inspectors of technical control departments (QCD) widely use gauges.
Caliber- a means of control that reproduces the geometric parameters of the elements of the product, determined by the specified limit lines or angular dimensions, and is in contact with the elements of the product along surfaces, lines or points. A product element is
structurally finished part of the product. For example: shaft, hole, groove, protrusion, thread, etc.
Caliber- this is a special technological equipment designed to assess the suitability of parts and products of mechanical engineering (permissive control). Gauge control has a higher productivity than measuring the actual dimensions of parts with measuring instruments. However, the design and manufacture of calibers is economically advantageous in large-scale and mass production.
With the help of calibers, parts are sorted into good and bad (marriage). Gauges do not determine the numerical value (actual size) of the controlled parameter, but only determine whether the element of the product is within the limits of the limiting dimensions. There is a correctable marriage, when the shafts are oversized, and the holes are undersized, and an irreparable marriage, when the dimensions of the shafts are underestimated, and the dimensions of the hole are too high.
Gauge control leads to a certain tightening of the tolerance for the manufacture of a part in comparison with the tabular value.
Gauges are used to control smooth cylindrical surfaces, for conical, threaded, keyed and splined surfaces, as well as to control the location of surfaces.
Distinguish calibers normal and limit.
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. have only a passing side.
Normal calibers (templates, location calibers) are used to control parts with a complex surface profile. The suitability of the part is judged by the size of the gap between its contour and the normal caliber for the uniformity of the clearance or under the probe.
Limit caliber- a gauge that reproduces the through and through limits of the geometric parameters of the product, i.e. these calibers have a passage ( ETC) and impassable ( NOT) sides. Limit gauges include smooth gauges for checking shafts and holes, threaded gauges, and others.
By purpose, calibers are divided into:
- working calibers, designed to check the dimensions of parts by workers and inspectors of the QCD;
- acceptance gauges- usually these are worn working gauges (their dimensions are within the wear tolerance), they are used by customer representatives;
- control gauges(counter gauges) are used to check the dimensions of working and acceptance gauges and to set the size of the adjustable bracket
Gauges are used to control the outer (covered) surfaces of the shafts, and plug gauges are used to control the internal (covering) surfaces of the holes.
Gauges - staples can be adjustable and non-adjustable. Adjustable calibers-brackets allow readjusting to another size (due to the movable insert) or restoring the size of the pass-through side as it wears out. Non-adjustable staples are used more widely, as they are rigid, cheaper and easier to manufacture.
8.2. CALCULATION OF EXECUTIVE DIMENSIONS
SMOOTH CALIBER
The execution size of the caliber is the size according to which the new caliber is made. Tolerances for the manufacture of the caliber are set "in the body" of the caliber in the form of a one-sided deviation: positive for the bracket and negative for the cork. Nominal sizes of pass calibers ETC and impassable NOT serve respectively as the limiting dimensions of the part.
Nominal pass gauge ETC corresponds to the maximum material of the tested object, i.e. for the shaft - the largest limit size, and for the hole - the smallest limit size.
Nominal size of non-going gauge NOT corresponds to the minimum material of the checked object, i.e. for the shaft - the smallest limit size, and for the hole - the largest limit size.
Tolerances for the manufacture and wear of smooth gauges are specified in GOST 24853 “Smooth gauges for sizes up to 500mm. Tolerances". Accepted symbols for tolerance fields H − for traffic jams and H 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 layouts of the tolerance fields of plug gauges are given in fig. 8.1.
All passing calibers have tolerance fields ( H and H 1 ) are shifted inside the tolerance field of the part by an amount Z − for plug gauges and Z 1 − for staple gauges. For nominal sizes over 180 mm, the tolerance zone of the non-going gauge.
T a b l e 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 | Cork Shape Tolerances | |||||||||
| 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 | ||||||||||||
| Z1 | 2,5 | 3,5 | ||||||||||
| Y 1 | 1,5 | 1,5 | ||||||||||
| H | 1,5 | 1,5 | 2,5 | 2,5 | ||||||||
| H1 | 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 | ||||||||||
| H1 | ||||||||||||
| Hp | 1,5 | 1,5 | 2,5 | |||||||||
| 9* | Z,Z 1 | IT2 | ||||||||||
| a,a 1 | ||||||||||||
| H | 2,5 | 2,5 | ||||||||||
| H1 | ||||||||||||
| Hp | 1,5 | 1,5 | 2,5 | 2,5 | ||||||||
| 10* | Z,Z 1 | IT2 | ||||||||||
| a,a 1 | ||||||||||||
| H | 2,5 | 2,5 | ||||||||||
| H1 | ||||||||||||
| 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 with (*) for all size ranges Y=Y 1 =0.
Rice. 8.1. Schemes for the location of tolerance fields for plug gauges for hole control:
a−up to 180 mm, grades 6…8 ; b− over 180 mm, grades 6…8;
in−up to 180 mm, grades 9…17; G− over 180 mm, grades 9…17
Rice. 8..3. Schemes of location of fields of tolerances of calibers-brackets
to control shafts of qualifications 9 ... 17: a−up to 180 mm; b− over 180 mm
is also shifted inside the tolerance field of the part by an amount a− for traffic jams and a 1- for staples. For sizes up to 180 mm a = a1 = 0.
For passing gauges, a wear tolerance is provided, which reflects the average probable wear of the gauge. For calibers up to quality 8, the wear tolerance goes beyond the tolerance field of the part by the value Y − for traffic jams and Y 1 - for staples. For calibers of coarser grades (9 ... 17), wear is limited by the passage 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.
During the operation of gauges-brackets, their suitability is checked with the help of counter-gauges, the shape of which corresponds to the shaft. Countercalibers have manufacturing tolerances HP , which are located symmetrically with respect to the middle of the tolerance fields of calibers for manufacturing and the wear limit. The layouts of the tolerance fields of the calibers-brackets are given in fig. 8..2 and 8.3). Counter gauges are made in the form of washers in a set of 3 pieces, as they check the through side of the working gauge ( K-PR), wear of the passing side (K-I) and impassable side ( K-NOT).
It is expedient to make control gauges only at specialized enterprises that produce staples in large quantities. In other cases, the control of staples is performed by blocks of end blocks of length.
Executive dimensions of calibers according to the corresponding scheme
the location of the tolerance fields are calculated according to the formulas of Table. 8.2.
T a b l e 8. 2
Formulas for calculation
limit and executive dimensions of calibers
| up to 180 mm | over 180 mm | |
| Traffic jams | (fig.8.1, a;8.1,in = (D m i n + Z + H/ 2) PR min = (D m i n + Z−H/ 2) PR out = (D m i n Y) NOT max = (D m a x +H/ 2) HE min = (D m a x - H/ 2) execution dimensions ( d) 1 PR = (D min + Z + H/ 2)-H NOT = (D max +H/ 2)-H | (Fig. 8.1, b;8.1,G) limit dimensions PR max = (D m i n + Z + H/ 2) PR m i n = (D m i n + Z−H/ 2) PR out = (D m i n Y + a ) NOT max = (D max-a +H/ 2) HE m i n = (D max − a − H/ 2) execution 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) limit dimensions PR max = (d max -Z 1 + H 1 /2) PR m i n = (d max -Z 1 -H 1 /2) PR out = (d max +Y 1 ) NOT max = (d m i n + H 1 /2) HEmin = (d m i n H 1 /2) execution 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) limit dimensions PR max = (d max - Z 1 + H 1/2) PR m i n = (d max - Z 1 −H 1 /2) PR out = (d max +Y 1 -a 1 ) NOT max = (d m i n + a 1 + H 1 /2) HE m i n = (d m i n + a 1 - H 1 /2) execution dimensions ( D) 1 PR = (d max - Z1−H 1 /2) + H 1 NOT = (d m i n + a 1 - H 1 /2) + H 1 |
| Counter gauges | (fig.8.2, a;8.3,a) execution dimensions ( d) K-I =(d max +Y 1 +H R/2) - H p K-PR = (d max – Z 1 + H R/2) - H p K-NOT = (d m i n + H R / 2) - H p | (Fig. 8.2, b;8.3,b) execution dimensions ( d) K-I = (d max +Y 1 -a 1 +H R / 2) - H p K-PR = (d max – Z 1 +H R / 2)- H r K-NOT = (d m i n + a 1 +H R / 2) - H p |
Note: Execution dimensions in fig. 2.1….2.8.
The execution sizes of calibers should be rounded off: for products of 6 ... 14 qualifications and all counter-calibers - up to 0.5 microns in the direction of reducing the production tolerance, the tolerance value of the caliber and counter-caliber is preserved; for products of 15 ... 17 qualifications - round up to 1 micron.
