How to measure thread pitch with a caliper. Threads. Differences between inch and metric threads. How to determine metric thread pitch

Inch threads are used primarily to create pipe connections: they are applied both to the pipes themselves and to metal and plastic fittings necessary for the installation of pipe lines for various purposes. The main parameters and characteristics of the threaded elements of such connections are regulated by the corresponding GOST, providing tables of inch thread sizes, which experts rely on.

Main settings

The regulatory document that stipulates the requirements for the dimensions of cylindrical inch threads is GOST 6111-52. Like any other, inch thread is characterized by two main parameters: pitch and diameter. The latter usually means:

outside diameter, measured between top points threaded ridges located on opposite sides of the pipe;
internal diameter as a value characterizing the distance from one lowest point of the cavity between the threaded ridges to another, also located on opposite sides of the pipe.

Knowing the outer and inner diameters of an inch thread, you can easily calculate the height of its profile. To calculate this size, it is enough to determine the difference between these diameters.

Second important parameter– step – characterizes the distance at which two adjacent ridges or two adjacent depressions are located from each other. Throughout the entire area of the product where the pipe thread, its step does not change and has the same value. If such an important requirement is not met, it will simply not work; it will not be possible to select a second element of the connection being created for it.

Familiarize yourself with the provisions of GOST regarding inch threads You can download the document in pdf format from the link below.

Table of sizes of inch and metric threads

You can find out how metric threads relate to different types of inch threads using the data from the table below.

Similar sizes metric and different varieties inch threads in the range of approximately Ø8-64mm

Differences from metric threads

According to their own external signs and characteristics, metric and inch threads do not have many differences, the most significant of which include:

profile shape of the threaded ridge;
procedure for calculating diameter and pitch.

When comparing the shapes of threaded ridges, you can see that in inch threads such elements are sharper than in metric threads. If speak about exact dimensions, then the angle at the top of the inch thread crest is 55°.

The parameters of metric and inch threads are characterized by different units of measurement. So, the diameter and pitch of the former are measured in millimeters, and the latter, respectively, in inches. It should, however, be borne in mind that in relation to an inch thread, it is not the generally accepted one (2.54 cm), but a special pipe inch equal to 3.324 cm that is used. Thus, if, for example, its diameter is ¾ inch, then in terms of millimeters it will correspond to the value 25.

To find out the basic parameters of an inch thread of any standard size, which is fixed by GOST, just look at the special table. The tables containing inch thread sizes contain both whole and fractional values. It should be borne in mind that the pitch in such tables is given in the number of cut grooves (threads) contained in one inch of product length.

To check whether the pitch of the thread already made corresponds to the dimensions specified by GOST, this parameter must be measured. For such measurements, carried out for both metric and inch threads using the same algorithm, standard tools are used - a comb, a gauge, a mechanical gauge, etc.

The easiest way to measure the pitch of an inch pipe thread is using the following method:

As a simple template, use a coupling or fitting, parameters internal thread which exactly correspond to the requirements given by GOST.
The bolt, the external thread parameters of which need to be measured, is screwed into the coupling or fitting.
If the bolt has formed a tight threaded connection with the coupling or fitting, then the diameter and pitch of the thread that is applied to its surface exactly correspond to the parameters of the template used.

If the bolt does not screw into the template or screws in but creates a loose connection with it, then such measurements should be carried out using another coupling or another fitting. The internal pipe thread is measured using a similar technique, only a product with external thread.

The required dimensions can be determined using a thread gauge, which is a plate with notches, the shape and other characteristics of which exactly correspond to the parameters of the thread with a certain pitch. Such a plate, acting as a template, is simply applied to the thread being checked with its serrated part. The fact that the thread on the element being tested corresponds to the required parameters will be indicated by a tight fit of the jagged part of the plate to its profile.

To measure the size of the outer diameter inch or metric thread, you can use a regular caliper or micrometer.

Slicing technologies

Cylindrical pipe threads, which are of the inch type (both internal and external), can be cut manually or mechanically.

Manual thread cutting

Thread cutting using hand tools, which uses a tap (for internal) or a die (for external), is performed in several steps.

The pipe being processed is clamped in a vice, and the tool used is fixed in a driver (tap) or in a die holder (die).
The die is put on the end of the pipe, and the tap is inserted into inner part the last one.
The tool used is screwed into the pipe or screwed onto its end by rotating a driver or die holder.
To make the result cleaner and more precise, you can repeat the cutting procedure several times.

Thread cutting on a lathe

Mechanically, pipe threads are cut according to the following algorithm:

The pipe being processed is clamped in the machine chuck, on the support of which a thread-cutting tool is fixed.
At the end of the pipe, using a cutter, a chamfer is removed, after which the speed of movement of the caliper is adjusted.
After bringing the cutter to the surface of the pipe, the machine turns on the threaded feed.

It should be borne in mind that inch threads are cut mechanically using lathe only on tubular products whose thickness and rigidity allow this to be done. Making pipe inch threads mechanically allows you to obtain high-quality results, but the use of such technology requires the turner to have appropriate qualifications and certain skills.

Accuracy classes and marking rules

A thread belonging to the inch type, as indicated by GOST, can correspond to one of three accuracy classes - 1, 2 and 3. Next to the number indicating the accuracy class, put the letters “A” (external) or “B” (internal). The full designations of thread accuracy classes, depending on its type, look like 1A, 2A and 3A (for external) and 1B, 2B and 3B (for internal). It should be borne in mind that class 1 corresponds to the coarsest threads, and class 3 corresponds to the most precise threads, the dimensions of which are subject to very stringent requirements.

Operational purpose of the thread

Mounting thread ensures complete and reliable connection of parts under various loads and under different conditions temperature conditions. This type includes metric.

Fastening and sealing thread designed to provide tightness and impermeability threaded connections(excluding shock loads). This type includes metric fine pitch, pipe cylindrical And conical threads and conical inch thread.

Running thread serves to convert rotational motion into translational motion. It absorbs great forces at relatively low speeds. Threads of this type include: trapezoidal, stubborn, rectangular, round.

Special thread It has special appointment and is used in certain specialized industries. These include the following:

- metric tight thread- thread made on the rod (on the stud) and in the hole (in the socket) along the largest size limits; intended for the formation of threaded connections with interference;

- metric thread with clearances- thread with necessary to ensure easy screwing and unscrewing of threaded connections of parts operating at high temperatures when conditions are created for setting (merging) the oxide films that cover the surface of the thread;

- hour carving(metric) - thread used in the watch industry (diameters from 0.25 to 0.9 mm);

- thread for microscopes- thread designed to connect the tube to the lens; has two sizes: 1) inch - diameter 4/5 І (20.270 mm) and pitch 0.705 mm (36 threads per 1І); 2) metric - diameter 27 mm, pitch 0.75 mm;

- ocular multi-start thread- recommended for optical instruments; thread profile - isosceles trapezoid with an angle of 60 0.

Figure 104 - Classification of threads

Advantages and disadvantages of threaded connections
Advantages of threaded connections:
- high load capacity and reliability;
- interchangeability of threaded parts due to standardization of threads;
- ease of assembly and disassembly of threaded connections;
- centralized production of threaded connections;
- the ability to create large axial compression forces on parts with a small force applied to the key.

Disadvantages of threaded connections:
- the main disadvantage of threaded connections is the presence of a large number of stress concentrators on the surfaces of threaded parts, which reduce their fatigue resistance under variable loads.

Distribution of axial load along thread turns

The axial load along the thread turns of the nut is distributed unevenly due to an unfavorable combination of deformations of the screw and nut (the turns in the most stretched part of the screw interact with the turns in the most compressed part of the nut).
The statically indeterminate problem of distributing the load along the turns of a rectangular thread of a nut with 10 turns was solved by Professor N. E. Zhukovsky in 1902.

The first turn transmits about 34% of the total load, the second - about 23%, and the tenth - less than 1%. It follows that there is no point in using too high nuts in the fastening joint. The standard provides a nut height of 0.8d for normal and 0.5d for low nuts used in lightly loaded connections.

To equalize the load in the thread, special nuts are used, which is especially important in connections operating under cyclic loads.

Metric thread

Metric thread(Fig. 120). The main type of fastening thread in Russia is a metric thread with a triangular profile angle a equal to 60°. The dimensions of its elements are specified in millimeters.

This is the main type of fastening thread, intended for connecting parts directly to each other or using standard products with metric threads, such as bolts, screws, studs, nuts.

According to GOST 8724-81, metric threads are made with large and fine pitches on surfaces with diameters from 1 to 68 mm - over 68 mm, the thread has only a fine pitch, and the fine pitch of the thread can be different for the same diameter, and the large one has only one meaning. The large pitch is not indicated in the thread symbol. For example: for a thread with a diameter of 10 mm, the large thread pitch is 1.5 mm, the fine one is 1.25; 1; 0.75; 0.5 mm.

According to GOST 8724-81, metric threads for diameters from 1 to 600 mm are divided into two types: with a large pitch (for diameters from 1 to 68 mm) and with a fine pitch (for diameters from 1 to 600 mm).

Coarse pitch threads are used in connections subject to shock loads. Threads with fine pitch - in connections of parts with thin walls and to obtain a tight connection. In addition, fine threads are widely used in adjusting and setting screws and nuts, as they make precise adjustments easier.

When designing new machines, only metric threads are used.

Metric thread is designated by the letter M:

· M16, M42, M64 – with large pitch

M16×0.5; M42×2; М64×3 – fine pitch

M42×3 (P1) - this means that the thread is multi-start with a diameter of 42 mm, a pitch of 1 mm and its stroke is 3 mm (three-start)

· M14LH, M40×2LH, M42×3(P1)LH – if you need to designate a left-hand thread, then after symbol put the letters LH

How to determine metric thread pitch

The easiest way is to measure the length of ten turns and divide by 10.

· You can use a special tool - a metric thread gauge.

Inch thread

Currently, there is no standard regulating the main dimensions of inch threads. The previously existing OST NKTP 1260 has been canceled, and the use of inch threads in new designs is not allowed.

This is a triangular profile thread with an apex angle of 55° (and equal to 55°). The nominal diameter of an inch thread (the outer diameter of a thread on a rod) is indicated in inches. In Russia, inch threads are allowed only in the manufacture of spare parts for old or imported equipment and are not used when designing new parts.

As mentioned earlier, the birthplace of standardized carving can be considered Great Britain with its English system measures The most prominent English engineer-inventor who was concerned with putting threaded parts in order was Joseph Whitworth ( Joseph Whitworth ), or Joseph Whitworth, that’s also correct. Whitworth turned out to be a talented and very active engineer; so active and enterprising that the first thread standard he developed in 1841 B.S.W. was approved for general use at the state level in 1881. At this point the carving B.S.W. has become the most common inch thread not only in Great Britain, but also in Europe. The fruitful J. Whitworth developed another whole line other standards for inch threads for special applications; some of them are still widely used today.

Determining the size of a fastener is quite simple. Is not it?

Yes, but not everything is as simple as it seems... If you don’t know in advance about the variety of fasteners and the features of their measurement, then you can easily buy something unnecessary or the wrong size. It would seem that determining the diameter, thickness and length of various fasteners should not cause problems. For example, for bolts, it is enough to measure the diameter and length of the threaded rod, and - done - there is a size. True, after turning all sorts of different bolts/screws in your hands, the question arises: “should I measure the length with or without a cap?” With nuts it’s even more “funny”: knowing that you may never find an M16 nut in your hands, where is the 16 mm size in this nut? Or maybe this nut is not M16 at all?

Let's try to figure it out...

The main parameters that determine the type and size of fasteners are: diameter, length and thickness (or height).

Most of today's Russian-language reference books, drawings and design documentation use designations borrowed from in English and alphabet.

Thus, the diameter of a fastener is usually denoted by a capital or small Latin letter "D" or "d" (short for English) Diameter), the length of the fastener is usually denoted by a capital or small Latin letter "L" or "l" (short for English) Length), the thickness is indicated "S" or "s" (short for English) Stoutness ), the height is indicated capital or small Latin letter"N" or "h" (short for English) Hi gh).

Let's look at the features of measuring the main types of fasteners.

Bolt Measuring

Bolts with metric threads are indicated in the documentation in the format MDxPxL , Where:

M - metric thread icon;
D - bolt thread diameter in millimeters;
P
L - bolt length in millimeters.

To determine the type and size of a particular bolt, you need to visually establish its type by comparing the bolt design with one of the standards ( GOST, DIN, ISO ) Then, having found out the type of bolt, sequentially determine all the listed dimensions.

To measure the diameter of a bolt, you can use a caliper, micrometer, or a template ruler.

The accuracy of a certain external thread diameter is controlled using a set of “PR-NOT” (pass-no-go) gauges, one of which should be easily screwed onto the bolt, and the other should not be screwed on at all.

The length of the bolt can be measured using the same calipers or ruler.

A tool such as a pedometer is commonly used to determine the thread pitch on a threaded fastener.

You can also measure thread pitch by measuring the distance between two threads using a caliper.

However, the accuracy of this method is satisfactory only for large thread diameters. It is more reliable to measure the length of several thread turns (for example, 10) with a caliper (or, in extreme cases, a ruler) and then divide the measurement result by the number of measured turns (in the example, by 10).

The resulting number must coincide exactly (or almost exactly) with one of the values of the thread series of thread pitches for a given thread diameter - this reference value is the desired thread pitch. If this is not the case, then most likely you are dealing with an inch thread - determining the thread pitch requires further clarification.

Depending on the geometric configuration of the bolt, the method of measuring its length may differ, and all bolts can be conditionally divided into 2 groups:

protruding head bolts
countersunk bolts

The length of bolts with a protruding head is measured without taking into account the head itself:

Hex Bolts GOST 7805-70, 7798-70, 15589-70, 10602-94;
Hex head reduced bolts GOST 7808-70, 7796-70, 15591-70;
High strength bolts GOST 22353-77;
High-strength hex bolts with increased wrench size GOST R 52644-2006.

Hex Head Bolts with Guide Rail GOST 7811-70, 7795-70, 15590-70.

Reduced hex head bolts for reamer holes GOST 7817-80.

Bolts with an enlarged semicircular head and a mustache GOST 7801-81.

Oversized Carriage Bolts GOST 7802-81.

Eye bolts GOST 4751-73.

The length of countersunk bolts is measured together with the head:

Countersunk bolts GOST 7785-81.

Countersunk Carriage Bolts GOST 7786-81.

Tire bolts GOST 7787-81.

An essential parameter for determining the type of bolt and its GOST standard (DIN or ISO) is the size of the head: turnkey size in the case of a hexagonal head, or diameter in the case of a cylindrical head; since there are bolts with a reduced head, with a normal head and with an enlarged head.

Measuring inch bolts

Bolts with inch threads are indicated in the documentation in the format D"-NQQQxL , Where:

D" - bolt thread diameter in inches - depicted as an integer or fraction with a symbol " , and also in the form of a number № for small thread diameters;
N
QQQ
L - bolt length in inches - depicted as whole number or fraction with sign" .

If you need to determine the thread diameter of an inch bolt, you need to divide the result of measuring the bolt diameter by 25.4 mm, which is equal to 1 inch. The resulting number must be compared with the nearest fractional size in inches (can be found in the table for inch threads with coarse pitch UNC ):

The thread pitch of an inch bolt is determined by counting the number of turns in one inch (25.4 mm) of thread. You can also use an inch thread gauge if you know in advance that the thread is inch. The length of an inch bolt must be measured in the same way as a metric one, and the result divided by 25.4 mm, which equals 1 inch. The resulting number must be compared with the nearest size in inches, separating the whole and fractional parts.

Measuring screws

Screws with metric threads are designated in the documentation similarly to bolts in the format MDxPxL , Where:

M - metric thread icon;
D - screw thread diameter in millimeters;
P - thread pitch in millimeters (there are large, small and especially small pitches; if the pitch is large for a given thread diameter, then it is not indicated);
L - screw length in millimeters;

First, by inspection we establish the type of screw being measured, determine its standard in order to determine the features of the measurement.

The thread diameter of the screws is determined similarly to the measurement of bolts.

Depending on the geometric configuration of the screw, the method for measuring its length may differ, and all screws can be divided into 4 groups:

screws with a protruding head (in Fig. 1, 2, 6);
screws with a countersunk head (in Fig. 4);
semi-countersunk screws (in Fig. 3);
screws without a head (in Fig. 5).

Pan Head Hex Screws GOST 11738-84;
Pan head screws GOST 1491-80.

Button head screws GOST 17473-80.

Countersunk head screws GOST 17474-80.

Countersunk screws GOST 17475-80.

Slotted set screws GOST 1476-93, 1477-93, 1478-93, 1479-93;
Hex socket set screws GOST 8878-93, 11074-93, 11075-93.

Square Head Set Screws GOST 1482-84, 1485-84.

Measuring studs

Studs with metric threads are indicated in the documentation in the format MDxPxL , Where:

M - metric thread icon;
D - diameter of the stud thread in millimeters;
P - thread pitch in millimeters (there are large, small and especially small pitches; if the pitch is large for a given thread diameter, then it is not indicated);
L - length of the working part of the stud in millimeters.

Determining the thread diameter of studs is identical to measuring the threads of bolts.

Depending on the GOST standard and the configuration of the stud, the method of measuring its length may differ, and all studs can be divided into 2 groups:

studs for smooth holes - the working part is the entire length of the stud - always have threads of the same length at both ends (in Fig. 1, 2);
studs with a screwed end - the working part is the shank without taking into account the screwed end (in Fig. 3).

For correct measurement The size of the stud must first be determined: does this stud have a screw-in end or not? After which it will become clear how to measure the length of the working part of the hairpin. The screwed end has, depending on the GOST standard, several fixed values, measured as a multiple of the diameter of the stud: 1d, 1.25d, 1.6d, 2d, 2.5d . The rest of the stud with the screwed end is its length.

Threaded studsDIN 975;
Dimensional studsDIN 976-1;
Studs for smooth holesGOST 22042-76, 22043-76;

Studs for smooth holes GOST 22042-76, 22043-76;
Studs for flange connections GOST 9066-75;

1d GOST 22032-76, 22033-76;
Studs with screw-in end length 1.25d GOST 22034-76, 22035-76;
Studs with screw-in end length 1.6d GOST 22036-76, 22037-76;
Studs with screw-in end length 2d GOST 22038-76, 22039-76;
Studs with screw-in end length 2.5d GOST 22040-76, 22041-76;

Measuring rivets

Rivets with a closing head - solid (for hammer) are indicated in the documentation in the format DxL , Where:

D - diameter of the rivet body in millimeters;
L - rivet length in millimeters;

Depending on the GOST standard and the configuration of a solid rivet, the method for measuring its length may differ, and all rivets can be divided into 3 groups:

rivets with a protruding head (in Fig. 1, 3);
rivets with a countersunk head (in Fig. 2);
rivets with semi-countersunk (in Fig. 4);

Rivets with flat (cylindrical) head GOST 10303-80;

Countersunk rivets GOST 10300-80;

Round head rivets GOST 10299-80;

Rivets with semi-countersunk head GOST 10301-80;

Tear rivets installed using a special gun are designated in the format DxL , Where:

D - the outer diameter of the body of the rivet itself in millimeters;
L - length of the rivet body in millimeters, excluding tear-off elements.

Breakaway rivets with a flat (cylindrical) head DIN 7337, ISO 15977, ISO 15979, ISO 15981, ISO 15983, ISO 16582;

Tear-off rivets with countersunk head DIN 7337, ISO 15978, ISO 15980, ISO 15984;

Measuring cotter pins

We will look at measuring three types of cotter pins:

Cotter pins GOST 397-79 - adjustable. The size of such a cotter pin is indicated in the formatDxL , Where:

D - nominal diameter of the cotter pin in millimeters;
L - length of the cotter pin in millimeters.

The nominal diameter of the cotter pin is the diameter of the hole into which this adjustable cotter pin will be inserted. Accordingly, the real diameter of the cotter pin itself, when measured, for example, with a caliper, will be smaller than the nominal diameter by several tenths of a millimeter - the GOST 397-79 standard specifies the permissible ranges for each conventional diameter of the cotter pin.

The length of the adjustable cotter pin is also measured in a special way: the cotter pin has two ends - short and long, and it is necessary to measure the distance from the bend of the cotter pin ear to the end of the short end of the cotter pin.

Cotter pinsDIN 11024 - needle-shaped. Such cotter pins have a fixed length according to the standard DIN 11024, so to determine the size of this type cotter pin, only the diameter of the cotter pin needs to be measured. Control of the length of the cotter pin must be carried out from the beginning of the straight end to the line of the center of the ring formed in the bend

Cotter pins DIN 11023 - quick-release cotter pins with a ring. Similar to cotter pins DIN 11024 Such cotter pins also have a fixed length according to the standardDIN 11023, so to determine the sizeFor this type of cotter pin, only the diameter of the cotter pin needs to be measured.

Measuring nuts

Nuts with metric threads are indicated in the documentation in the format MDxP , Where:

M - metric thread icon;
D - diameter of the nut thread in millimeters;
P - thread pitch in millimeters (there are large, small and especially small pitches; if the pitch is large for a given thread diameter, then it is not indicated);

Measuring the thread diameter of a nut is not as easy as it seems at first glance. The fact is that the designated size of the nut, for example M14, is the outer diameter of the bolt that is screwed into this nut. If you measure the internal threaded hole in the nut itself, it will be less than 14 mm (as in the photo).

The obtained measurement result does not make it possible to immediately unambiguously determine the thread diameter (considering that each thread diameter can have several thread pitch values, you can easily make a mistake in determining the nut thread diameter if you use only one measurement of the internal threaded hole nuts). If it is possible to measure the counter bolt, screw, fitting, it is better to measure it and immediately determine the thread of the nut.

The resulting measurement value of the internal thread of the bore hole in the nut is the internal diameter d vn thread profile in conjunction with a bolt corresponding to a given nut ( on which it is screwed).

M ― outer diameter of the bolt (nut) thread ― designation of the thread size

N - height of the metric thread profile, Н=0.866025404×Р

R — thread pitch (distance between the vertices of the thread profile)

d CP - average thread diameter

d VN - internal diameter of the nut thread

dB - internal diameter of the bolt thread

To unambiguously determine the diameter of a metric nut thread, it is necessary to know the correspondence of the internal diameter d vn with external thread diameter M at the mating bolt (and this is the required thread size of the nut). To do this you will need a lookup table:

The accuracy of a certain thread diameter is controlled using a set of “PR-NOT” (pass-no-pass) gauges, one of which should be easily screwed into the nut, and the other should not be screwed in.

There is a significant variety of nut types. Initially, the type of nut can be determined visually. To clarify the standard, it is often necessary to measure the height of the nut, since with one geometric configuration they can be low, normal, high and especially high.

Another parameter that you need to pay attention to when classifying a hex nut is the “wrench” size, since there are nuts with a reduced “wrench” size, with a normal and an increased size.

Measuring the thread pitch of a nut is done in the same way as a bolt - using a thread gauge or counting the threads on the measured segment. But measuring the thread pitch of nuts is difficult due to the fact that it is difficult to determine the tightness of the thread gauge comb to the thread profile, and there is always the possibility of an error in the case when you do not know in advance: is the thread metric or inch? You can make a mistake due to the fact that some metric thread sizes are almost the same as inch threads and metric bolts can be screwed with inch nuts. Characteristic sign such twisting means excessive play - the nut dangles on the bolt, as if the thread had failed. The best way to avoid mistakes when determining the thread of a nut is to take all measurements from the bolt (screw, fitting) that matches the nut.

Measuring inch nuts

Nuts with inch threads are indicated in the documentation in the format D"-NQQQ , Where:

D" - nut thread diameter in inches - depicted as an integer or fraction with a symbol " , and also in the form of a number№ for small thread diameters;
N - number of thread turns in one inch;
QQQ - type of inch thread - an abbreviation of three or four Latin letters;

The best way Measuring the thread of an inch nut is also measuring the thread of the corresponding counter bolt (screw, fitting). If there is none, but it is known in advance that the thread is inch, then it is necessary to use a thread gauge for an inch thread of this type or, if it is not known which of the inch threads in the nut, perform a procedure similar to determining the metric thread of a nut, dividing the measurement results by 1 inch (25.4 mm) and comparing them with a number of fractional values of inch threads given in the tables in the article.

Washer measurement

Washers are indicated in documentation most often in the format D , Where:

D - diameter in millimeters of the metric thread of the bolt corresponding to this washer.

By measuring the inner diameter of the washer with a caliper or ruler, you will get a size larger than in its designation. This is quite natural: after all, it is necessary to freely insert a bolt or screw into the washer, and for this there must be a gap between them.

For example: when measuring a flat washer of size 16 (for the thread of an M16 bolt), the caliper will show a hole diameter of 17 mm.

In the most general case, the size of this gap is determined by the accuracy of the washer. Thus, if the size of the washer is unknown in advance, then, after measuring the diameter of the hole, it is necessary to select from the table of the standard for this washer (GOST, OST, TU, DIN, ISO) the nearest fixed standard size- this is the size of the washer.

IN modern world widespread received threaded connections. It is characterized by high reliability and practicality in use. They stand out quite a large number of various parameters, which can be used to determine the parameters of the fastener in question. The most important step can be called. It is indicated on almost every drawing and various technical documentation.

Concept of thread pitch

Threads are used to connect the most various products. To determine the bolt thread, you need to consider the distance between the same sides of the profile. The features of this concept include the following points:

To determine the main parameters, a measurement is required.
An inaccurate result can be determined by using a ruler.
To increase the accuracy of measurements, you need to analyze several threads. That is why, depending on the length of the threaded surface, an analysis of 10 to 20 turns is carried out.
It is recommended to take measurements in millimeters. In some cases the number is converted to inches.

The distance between the depressions can be measured using a special tool. The thread gauge is represented by a combination of special steel plates that have special cutouts. Various values are applied to the surface.

Measurement methods

There is quite a large number in various ways determining the thread pitch. All of them are characterized by their own specific features that need to be taken into account. Common methods include:

Using a regular ruler.
The use of a special tool that can be used to determine the value in question. A thread pitch meter can be purchased at a specialty store.
A caliper is a precision instrument. It is used quite often due to high precision and versatility in use.

All of the above methods allow you to obtain fairly accurate data. The easiest way to take measurements is to use a thread-finding tool, but you can get by with a regular caliper.

The process of measuring turns

When considering how to determine the thread pitch, the features of the chosen method should be taken into account. When using a ruler it is enough:

Measure the length of the rod on which the profile was applied. It is worth considering that by measuring the entire length of the rod, and not just part, you can determine a more accurate result.
Count the number of turns.
Take depth measurements to determine the main parameters of the threaded connection.

In this way, only the average can be determined. If errors were made during the cutting process, the distance between them may differ slightly.

An example of measurements looks like this:

20 turns are counted.
We measure the length of the rod, for example, the indicator was 127 mm.
We divide 20 turns by the length of the rod, the result is 6.35 mm. It corresponds to the pitch of the threads in millimeters.

To convert to inches, simply divide the calculated value in millimeters by 25.4. The result will be 0.25 or ¼ inch. If you measure yourself, there may be an error, so the result is rounded to an approximate standard value.

You can also find special templates on sale that can be used to check the features of the thread. This procedure is quite simple to perform:

The most suitable template is selected. On sale you can find simply a huge number of special templates, which are represented by a plate with a certain profile. Such an element is not expensive; you can purchase it in various specialized stores.
It is applied to the surface to monitor basic indicators. The template must fit without obstacles, and between the plate and work surface no free space should be created.

If the template easily fits into the grooves, then the basic parameters of the surface can be determined.

In addition, you can take measurements using a caliper. This tool has become widespread. Step by Step Actions look like this:

The depth gauge determines the height of the rod.
The next step is to count the number of turns. This is quite difficult to do; you can use a marker to indicate the profile threads that have already been counted.
The information obtained allows you to calculate the tangent of the angle of inclination.

It is possible to determine the indicator in question by direct measurement between adjacent vertices. It is recommended to clean the surface. Otherwise, it is almost impossible to get an accurate result.

Nuances of measurement

There are a few guidelines to keep in mind when using a caliper. An example is the information below:

If there is a plate between the head and the end part of the product, then in this case it is recommended to use the main measuring scale and depth gauge. With such a process, it is possible to obtain indicators of the thickness of the washer, the height of the head, and the thickness of the intermediate element. Such data allows you to calculate the main parameters of a threaded connection.
The accuracy of the results obtained can be significantly increased by cleaning the surface from various contaminants. To do this, you can use an abrasive material or special liquids to remove corrosion.

You can carry out the procedure in question yourself. As a rule, there are no problems with this.

In conclusion, we note that manufacturers indicate the pitch and many other important indicators. As a rule, they are applied to the head or other element.

Without fasteners, a master is like without hands: he has to constantly deal with the fixed connection of parts of various structures. Bolts, screws, nuts, screws, washers are the most common fasteners. In work, it is often important to know the size of the bolt in advance.

You will need

Calipers;
- ruler.

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Instructions

Bolts and nuts similar to modern ones appeared around the middle of the 15th century. They were made entirely by hand, and therefore each nut-bolt combination was unique. Classic version The connection between these two parts has been improved over the years.

Among the latest industrial achievements is the development of special electronic devices that can automatically control the tightening forces of this type of fastener.

The modern bolt is a sought-after fastener. Together with the nut, it is intended for detachable connection of parts and is a cylindrical rod with an external thread at one end and a head at the other. The head may be different shapes: square, oval, cylindrical, conical, six or four sides. Most of state standards for fasteners, including bolts, provides for the possibility of producing similar products (by general appearance, by purpose). The only difference will be in the type of bolts and their design. The size of the bolt depends on the purpose and is primarily related to the outer diameter of the thread, since the bolt is a threaded fastener. To determine the bolt diameter, measure the outer diameter of the bolt with a caliper. If the thread is not applied along the entire length of the rod, then the diameter of the bolt in its “bald” part is approximately the same as the diameter of the thread when measured at the tops of the turns. What is the bolt length? As a rule, when designating a product, the length of its rod is indicated. Thus, the height of the head is not taken into account. Measure the length of the rod - get the length of the bolt. If you order an M14x140 bolt in metric measurement, this means you need a bolt with a thread diameter of 14 mm and a shaft length of 140 mm. In this case, the total overall length of the product, taking into account the height of the bolt head, for example, 8 mm, will be 148 mm. Another parameter is the bolt thread pitch. Measure the distance between two nearby (adjacent) thread vertices and you will get the required size. For example, an M14x1.5 bolt is a bolt with a diameter of 14 mm and a thread pitch of 1.5 mm. Another size characteristic of some types of bolts is the length of the threaded end. To find out, measure the part of the rod that is intended for screwing on the nut. There are many standards that set out technical requirements for fasteners. For example, for flange connections (namely, bolts are used for them), they are set out in GOST 20700-75. Both the design and dimensions of the fasteners are regulated by GOSTs 9064-75, 9065-75, 9066-75. How simple

Measurements during the design and manufacture of threaded connections

The “bolt-nut” type connection is one of the most common in mechanics. When designing and manufacturing structures, the problem of how to measure a bolt with a caliper is often difficult.

Before starting work, it is worth remembering that the main dimensions of a bolt/nut are the length of the product and the diameter of the thread. A standard bolt of any design does not require such measurements. It’s a different matter when the bolt is made at home, or you need to measure the fastener without dismantling the connection. The following situations are possible here:

Measurements of the dimensions of the pattern on the protectors

How to measure tire tread if you need to assess the degree of wear? A depth gauge will help, which takes measurements along the entire tire tread. It should be taken into account that wear is almost always uneven, and the number of measurements should be at least 3...5, and on evenly distributed areas of the tire tread for assessment. Before measurements, the tire should be thoroughly cleaned of dirt, dust and fragments of small stones stuck inside.

Sometimes you need to solve the problem of how to measure the tire tread with a caliper to determine the degree of uniformity of wear. This establishes the wear of the tread tires not only in depth, but also along the radius of transition from the circle of protrusions to the circle of depressions. They do this. The depth of the pattern on the new tire tread is measured, and then the linear size of the visually changed zone on the used part. The difference will determine the degree of wear and help you make the right decision about replacing the wheel.

All measurements are made with a depth gauge, which must be installed strictly perpendicular to the tire tread.

Measuring tread wear with a Columbian

Diameter measurements

How to measure diameter with calipers? There are parts with a constant and variable cross-section along the length. The latter include, in particular, reinforcing bars. How to measure the diameter of reinforcement with a caliper? It all depends on the reinforcement profile, which can be:

ring;
sickle-shaped;
mixed.

It is easiest to measure such reinforcement parameters in the second case. First, use external measuring jaws to determine the height of the protrusions of the profile, and then use a depth gauge to determine the size along the depression. Measurements must be taken in two mutually perpendicular directions, since reinforcement, and even not produced at specialized enterprises, often has an oval cross-section. After this, using tables of standard reinforcing profiles, they find the maximum suitable value(special precision is not required here). How to measure the diameter of reinforcement with a caliper if it has a different type of profile? Here, instead of the diameter of the protrusions, the diameter of the protruding part of the crescent-shaped notches is determined, and then proceed in the same way as in the previous case.

When measuring the internal dimensions of pipes, use the internal measuring scale of the tool. How to measure the thickness of a pipe with a caliper, especially if the gap is small? It is enough to calculate the difference between external and internal diameters and divide the result by two.

Linear dimensions measurements

How to measure linear dimensions using a caliper? It all depends on the material of the part/workpiece. For rigid elements, the product is pressed tightly against some support plate, after which the measurement is taken with the external measuring jaws of the tool. You must first determine the suitability of the existing type of caliper for use. For example, the main measuring scale on the rod should be less than 25...30 mm longer than the part (taking into account the own width of the jaws). When using a depth gauge, this value is even smaller, since the length of the frame should also be taken into account (for the most common tools 0-150 mm and an accuracy of 0.05 to 0.1 mm, this parameter is taken to be at least 50 mm).

How to measure the cross-section of a wire with a caliper? Non-metallic products are flexible, and therefore significantly distort the result obtained in the usual way. Therefore, a rigid steel part (screw, nail, piece of rod) should be inserted into the cambric, and then the cross-sectional diameter of the wire should be determined using external jaws. Do the same if you want to know inner size wires.

The question - how to measure a chain with a caliper - is often asked by cyclists, since chain wear, defined as the distance between its adjacent links, makes it possible to decide whether to replace the product. The outer jaws are set at a distance of 119 mm and inserted into the link, after which they are stretched to the sides until further increase in size is impossible (to facilitate the work, the chain can be pre-loaded with a tensile force). The deviation from the original size will show actual wear, which must then be compared with the maximum allowable.

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A nut is a fastener for a screw drive or threaded connection. They differ from other parts by having a threaded hole. Together with the bolt (screw), it forms screw pair. The nuts that screw onto a stud or bolt make up a bolted connection. Most often, hexagonal nuts are produced in factories. They are specially made for a wrench. Also on sale you can also find nuts with wings, square shapes, round ones with a notch and other shapes. They are made from automatic steel. For this purpose, special automatic machines are used.

It is worth noting that the nuts also differ in their strength class. Thus, for nuts made of carbon alloyed or unalloyed steels, a strength class of 4-6, 8-10 is established. For nuts with a normal height (more than 0.8d), strength class 12 is established. Those nuts that have a height of 0.5d-0.8d have strength class 04-05. The shape of the nuts also differs. There are wing open and closed (defined by GOST 3032-76), hexagonal crown round, hexagonal slotted (defined by GOST 6393-73, 11871-80). There are lower hex nuts, especially high, high and normal height. Hexagonal castle, slotted and hexagonal nuts can be lightweight (with small external dimensions), as well as normal (photo 1).

The most common are hex nuts. Castle and slotted nuts are used when it is necessary to lock the nuts with cotter pins. Round nuts are used to fasten various parts, but for connections that need to be constantly assembled and disassembled, it is best to use wing nuts, which can be easily tightened even without using a special wrench. By the way, if you need to use a large number of nuts in your work, then it is more advisable to take lightweight ones, since they will save significant weight. When it is clear that the bolt shaft is underloaded in tension, it is best to use low nuts. To protect the threads from wear and tear, as well as crushing during frequent unscrewing, use especially tall or tall nuts (photo 2).

The size of the nut should be understood as the distance that is formed between the parallel edges. Dimensions are regulated by GOST. Thus, nuts of accuracy class A, low hexagonal, high precision have the dimensions specified in GOST 5929-70. The size of accuracy class A hex nuts is specified in GOST 5916-70. In other GOSTs - GOST 5916-70, 5915-70, the dimensions of nuts of accuracy class B, hexagonal low and hexagonal are given. All sizes can be viewed in the tables given in GOST (photo 3).

The most popular nut, as already mentioned, is the hexagonal one. These nuts vary in size: M 6, M 8, M 10, M 12, M 16, M 24, M20, M30, M27, M 36, M 52, M 48, M 42. To screw such a nut onto a bolt, you need nuts keys. Today there are fifteen types of such keys. There are gas, end, cap, carob, adjustable, balloon, combination, hex and spark plug types on sale, designed for spark plugs (photo 4).

The sizes of wrenches are also different. For the nut, the thread size will play a role, so they can have sizes M1.6 - M110. The distance between the jaws of wrenches ranges from 3.2 millimeters to 155 millimeters. The length of the handle can be from one hundred and fifty millimeters to five hundred millimeters. Combination wrenches are popular - socket wrenches on one side and open-end wrenches on the other. It is also worth noting that special nuts are used in industry today. These are hex nuts that are used to seal joints and fasten wheels on vehicles (photo 5).

Even a person who is far from technology often has to unscrew and tighten screws, bolts, nuts (hardware - this is what these are often called in abbreviated form) hardware) with a tool designed for this purpose - wrenches. Each key is marked with the size of its working part, simply the throat. But the corresponding value - the wrench size - denoted in technical reference books by the letter S (the distance between opposite parallel edges on a nut, bolt or screw head), is not indicated on any fastener. As a rule, this data is not included in the operating and repair instructions attached to any equipment, even in the designations and drawings, although they contain plenty of other information about fasteners: the thread size and its pitch are indicated, sometimes the length and even type of heat treatment, often also tightening torque. But basically these data are constructive, and they are needed for the manufacture of parts. During adjustment, repair or assembly work, the above thread parameters, except for the last, are unclaimed. For a mechanic, it is much more important to know what size of throat a wrench is needed for the head of a particular screw or bolt and nut (or, as the professionals say, “a wrench for how much”).

When the nut or bolt head is in plain sight and in an easily accessible place, it is not difficult to determine “how much” a key is needed - an experienced technician will recognize this at a glance, and an inexperienced one can “calculate” using a caliper or by selecting keys: from two - This can usually be done three times.

If the fastener is in hard to reach place, and even “behind the eyes” (which happens very often), then determining the size of the turnkey hardware head has to be done by touch, when even a professional can easily make a mistake. Trouble will not happen if the master tries to work with a smaller key - it simply will not fit on the head. If the key turns out to be large, then “cutting off” the ribs of the head with it, as they say, is a piece of cake. In addition to the fact that the part will be irreparably damaged, then unscrewing the fasteners even with a special tool will be a considerable problem.

To determine the “turnkey” size “by sight”, it makes sense to refer to the information about the thread of the fastener specified in the instructions. Indeed, according to GOST, each thread corresponds to two close sizes of the head of a turnkey fastener: the main one and the reduced one, and the difference in their values is small. On average, the turnkey size is approximately 1.5 times larger than the outer diameter of the thread (see Table 1) and you can already focus on it. And although a reduced wrench size is assigned by designers less often than the main one, you should try to unscrew the fasteners “behind your eyes” for the above reasons, still using a smaller wrench: if it doesn’t fit, then you can safely work with a wrench corresponding to the main size - it won’t break off (of course, provided that the fasteners are not rusty). The wrenches are usually also made according to the same principle: at one end the gap (open for open-end wrenches, closed for socket and ring wrenches) corresponds to the main size of the head of the fastener, and at the other - a reduced one. The only ones that fall out of this series are combination wrenches, which have the same size jaw at both ends, only one is open and the other is closed (circular), and adjustable wrenches.

Matching the dimensions of the turnkey fastener to its nominal metric thread diameter

When working with fasteners, to ensure their safety, the tool has vital importance, therefore, you should use only serviceable keys: their jaws should not be widened and their jaws should not be wrinkled. Keys with such defects must be removed from the working kit. In addition, seemingly similar tools differ significantly in the quality of the metal and the profile of the jaws. The last condition directly affects the distribution of forces on the faces and edges of hardware.

Fasteners are designed for a specific tightening torque when assembling the product. However, often the effort when disassembling, especially “stuck” or rusted threaded connections, exceeds it many times over. In these cases, it is better to use appropriate socket or ring (professionals call them ring) wrenches rather than open-end wrenches. Moreover, you cannot use an adjustable wrench, as well as when unscrewing small (less than S10) nuts, bolts and screws.

Combination pipe wrench.

If the edges of the fastener are severely damaged by corrosion or for some reason are “rolled”, in order to still unscrew it, you need to grind off the edges of the key by a “number” less. Then, after saturating the threaded connection with a special liquid (or, in extreme cases, kerosene) to soften the rust and wait a while, try to unscrew the part again. Another way (but not the last) to unscrew a bolt or screw with a damaged head is to make a slot between the opposite edges using a strong screwdriver and try to unscrew the fastener with this tool. And finally, use a pipe wrench for this. By the way, in the range of the latter there are now those that do not damage the edges and edges of fasteners even when big moments unscrewing. For small nuts, you can use special pliers.

When you have to regularly adjust and repair the same equipment (for example, a personal car), it will be useful to draw up a table of turnkey sizes of fasteners of the main adjustable units, devoting special time to this or as you turn to adjusting a particular mechanism or unit.

Regular key heads:

Key heads with dynamic profiles:

a - end; b - caps.

Forces on the edges and ribs of fastening threaded parts from socket (a) and ring (b) wrenches with different internal profiles:

I - concentrated; II - distributed.

Table 2 shows the turnkey dimensions of the main and adjusting threaded connections for the VAZ-2105 car.

Some fasteners and their turnkey sizes in VAZ cars

Since we are talking about cars, it is worth noting that the so-called “balloon” “19” and “spark plug” “21” keys are of particular importance in the tool kit of “Zhiguli” (and other cars).

The first one is made quite uniquely and stands out from the entire set of keys. Even those who have little knowledge of technology will recognize it: it is cap-shaped, with a curved handle-lever, the end of which is made in the shape of a screwdriver blade. Once upon a time, this wrench was used to remove chrome wheel covers that modern cars they don't put it on anymore. It would be advisable to sharpen it a little and thus have a strong screwdriver in the kit. In addition to loosening and tightening wheel bolts, this wrench can also be used when working with other related fasteners. If necessary, the wheel bolts can be unscrewed with a regular (socket or even open-end) wrench “19”.

The second, a “spark plug” wrench, is similar in appearance to similar tubular socket wrenches with the same diametrical hole for the wrench. It even retains the ratio of 1.5 times the diameter of the thread being turned away (14 mm) to the distance between the opposite edges of the key (21 mm). If we look again at Table 2, it will become clear that the key is non-standard, and there is no special key or other key with the same size in the kit. The thread on the candle, although standard (14x1.25), is not recommended.

And about one more key - a regular open-end “10”. It is better to always keep this key, like a fire extinguisher, “at hand” - since it is used to loosen the nuts of the battery terminals. After all, if necessary, for example, when short circuit V electrical circuit or (which has now also become relevant) to turn off an alarm that has gone off out of the blue (if it doesn’t “listen” to the key fob), this must be done very quickly.

It should be noted that the automotive tool kit does not contain wrenches for all sizes of fasteners. Therefore, when you need to crawl under a car (on a hole or overpass), it’s a good idea to check that you have all the necessary tools with you, otherwise you’ll have to crawl out from under it with nothing. The same must be done if you intend to disassemble some component or assembly for repair or maintenance. In addition, very often, to disassemble assemblies without damage, some universal and even special devices. Without all this, disassembly may be impossible or even in vain.

One notable point: fasteners with a turnkey size of 13 appeared in our country along with the Zhiguli car, the prototype of which, as you know, was the Italian FIAT-124. With their appearance, hardware with turnkey sizes of “12” and “14” lost their position.