What thread is used in pipe connections

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Connecting sections of water and gas pipes using threaded connections is a reliable and convenient way. To do this, a recess in the form of a spiral with a constant depth and a constant distance between adjacent grooves is created on the outer surface of the pipe and on the outer or inner surface of the connecting pipe of the shut-off valve or fitting. In order for the connection to be durable and not leak, the threaded profiles on the parts being connected must match in their parameters. In everyday life, during the construction of private houses and renovation of apartments, cylindrical inch pipe threads of ¼, ½ and 1 inch have become the international standard. Pipe thread

What is pipe thread

Pipe threads meet international standards; sanitary products use cylindrical inch threads that meet the standard of Whitworth, an English engineer who patented it in 1841. The designation of pipe threads according to GOST is the symbols “Tr.” In addition to inch threads, metric threads are also common in Russia. It has become more widespread in industry. There is also a tapered pipe thread. It is used for particularly tight connection of pipes operating under heavy mechanical loads, and is used mainly in gas and oil production, in drilling rigs. Types of pipe threads and designation on drawings When building a house and renovating an apartment, consumers are faced with inch cylindrical pipe threads.

Thread types

For inch threads, the diameter is indicated in inches (an inch is equal to 25.4 millimeters) and simple fractional fractions of an inch, and the pitch is the number of turns that fit in one inch. There is another important point - the so-called. "pipe inch". The thickness of its walls is added to the inch value of the internal diameter of the pipe. For an internal diameter of one inch, the result is 33.29 millimeters. A ½-inch pipe, accordingly, will have an outer diameter of 21.25 millimeters. Pipe thread is inch. For a metric thread, the diameter is indicated in millimeters, and the pitch is also indicated in millimeters - the distance between adjacent turns. This distance is measured between the ridges or between the valleys of the profile. In addition to the nuances of the designation, inch profiles are characterized by sharper ridges and valleys and slightly rounded tops of the teeth. The metric profile is based on an equilateral triangle with angles of 60°; for an inch profile, these angles are 55°. Due to this difference in the profile, it will not be possible to combine metric and inch threads in one connection; you will need a special adapter. Adapter from metric to inch threads In addition to metric and inch, When connecting pipes, round threads, or the so-called Edison profile, are also used. The profile represents an alternation of convex and concave arcs with the same radius. Round knurling provides greater wear resistance and is used in connections that will have to be screwed and unscrewed repeatedly. The most popular in plumbing, pipes and fittings for an apartment or house is cylindrical pipe threads. The most popular thread diameter is ½ “Schematic representation of Edison’s thread. ¼” thread is also widespread. It is used in mounts for photo and video cameras, lighting and other auxiliary photographic equipment.

Pipe thread sizes

Inch threaded connections come in the following sizes:

• D internal: 1/16" to 6".
• P (pitch), in turns / inch 28, 19, 14, 11 (if converted to mm, then: 0.907, 1.337, 1.814, 2.309).
• D along the profile crest, in millimeters: 7.7-163.8.
• Describes GOST 6357-81 or ISO R228.

Download table of pipe threads

Download GOST 6357-81

Key characteristics of cuts

The main characteristics of any thread, including pipes, are:

• Pitch (P, pitch) - the distance between adjacent turns.
• External diameter.
• Inner diameter.
• Stroke is the distance that the fastener moves in the longitudinal direction in one full revolution. For single-start knurling, the stroke is equal to the step, for multi-start knurling - the step multiplied by the number of passes.

Inch thread diameter

This data is enough to select a compatible fitting or fitting in the store. To make a threaded connection on a screw-cutting lathe or milling machine, you will need other characteristics of the thread, such as profile angles and others.

How to determine the diameter and type of cutting

When selecting a compatible threaded connection for an existing product, it is necessary to determine its parameters. This can be done in the following ways:

• Use measuring gauges. Special calibrated flat combs are inserted one by one into the profile turns until a complete match of the profiles is achieved. To determine the parameters of internal threads, cylindrical gauges are used. Each caliber is engraved with the profile it fits.
• Measure the parameters diameter and pitch with a caliper, determine the profile using the tables.

Pipe thread measurements should be carried out with a high-precision verified tool down to hundredths of a millimeter.

Cutting equipment

For cutting, depending on the chosen technology, the following equipment is used:

• Screw-cutting lathes.
• Sets of dies, taps and cranks (done manually).
• Thread rolling machines (for cold or hot rolling).
• Milling machines or machining centers.
• Grinding machines.

Milling machine Screw cutting lathe

Lathes, screw-cutting and milling machines, hot rolling units are used only in production conditions. For domestic applications, sets of dies and taps or a KLUPP device are used, which does not require changing dies during successive passes. The cutting combs, covering the pipe on three sides, can be gradually pushed into the body, providing a finishing passage.

Threads used in everyday life

When building houses and renovating apartments, the most common inch pipe threads are:

• ½ and ¼ - with a pitch of 14 turns/inch (or with a pitch of 1.814 mm)
• and also: 1, 1¼, 1½, 2 with a pitch of 11 turns/inch (or with a pitch of 2.309 mm)

Less commonly used is a plumbing round thread, or Edison profile.

The 11 TPI pitch is maintained on pipes ranging from 2 to 6 inches in diameter.

Pipe cylindrical thread

A ½ pipe is the main diameter for intra-house and intra-apartment wiring; it provides sufficient water pressure from the main; most faucets for bathtubs, toilets, showers, washing machines and dishwashers are designed specifically for this connecting size.

¼-inch pipes are used for the last meters of wiring to plumbing fixtures that do not require high pressure and flow, for example, sink faucets. ¾-inch pipes are used at the entrance to the apartment or at the distribution manifold of the pumping station of the local water supply system.

Pipes of 1 and 1 ½ inches are used much less frequently in the construction of large cottages equipped with swimming pools.

Making pipe threads

The methods for making pipe threads depend on the equipment available, the production volume and the required accuracy. Thus, knurling is used mainly for the production of large series of products, since it guarantees high productivity and low cost of the operation.

Thread cutting methods

• Cutting on a screw-cutting lathe is characterized by high accuracy and very low productivity. Used in individual and small-scale production.
• Cutting with dies and taps also has low productivity and is usually carried out in several passes using tools of varying degrees of accuracy.
• Knurling is the main industrial method; the formation of a profile occurs not due to the removal of chips, but as a result of plastic deformation of the metal by rolling dies. High productivity is ensured by automating the operation of removing and placing the part on the machine.
• Thread milling is performed on specialized thread milling machines.
• Casting. Advanced casting methods - high pressure casting and powder metallurgy - make it possible to obtain an accurate and durable thread profile directly from the casting, without subsequent machining

In construction and repair conditions, as a rule, only the manual method is available.

Pipe thread pitch determination

To determine the pitch of a pipe thread, a specialized measuring tool is used - a thread gauge.

In its absence, you will have to use a ruler (for large diameters) or a caliper.

When measuring metric pitch, measure the distance between, for example, five threads, and then divide it by 5.

Inch thread sizes

In the case of an inch one, they calculate how many turns will fit at a distance of 25.4 millimeters.

The diameter can also be measured very roughly with a ruler; for an accurate determination it is better to use a caliper

Pipe thread cutting

For manual slicing, a special device is used - KLUPP. This is a cylindrical body with two gate handles, inside which there are adjustable movable comb cutters, which, gradually moving out of the body, deepen the profile until a full profile is achieved.

DIY thread cutting

In the absence of such a device, you can cut the thread with a simple collar with a tap or die clamped in it. The die is fixed in the collar with three centering bolts with conical ends, for which recesses are provided on the die. First, they use rough taps or dies, gradually changing them to fine ones.

Manual cutting is easy for pipe diameters up to 1 inch; for larger diameters, considerable physical effort must be applied.

In addition, it becomes quite difficult to start the first thread without distortions. To cut large diameters and facilitate the insertion of the die into the thread, a threaded bushing is used.

The device is a liner, on the outer surface of which a thread has already been cut. At the end of the turns, a ledge is made on the liner, reducing its diameter to the internal diameter of the pipe. It is inserted into the inner hole of the pipe before the thread begins and is expanded there by a conical expansion mechanism.

The die is easily screwed onto the coils of the liner, driven along it and easily fits onto the first thread of the thread cut on the pipe. Several threads on the insert reliably hold the die from distortion.

Source: https://pellete.ru/trub/trubnaya-rezba.html

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The difference between metric and pipe threads and their parameters

Threaded connections are one of the main methods of joining elements of pipelines; sometimes when installing lines with pipes with your own hands, you may encounter different types of them. Therefore, when selecting materials and components for independent installation of pipelines, it is useful to know the difference between metric and pipe threads.

According to accepted standards, pipe threads are measured in special and ordinary inches; there are several types of them, which, depending on their purpose, differ in certain parameters. When doing independent manual or mechanical cutting on lathes, these differences must be taken into account in order to correctly select the sizes that provide the highest quality joints for certain operating conditions.

Fig.1 Profile dimensions of tapered thread

Why in inches?

Although the metric measurement system is ubiquitous in countries around the world, and the thread pitch is tied to a millimeter, all modern plumbing, pumping, heating equipment and other systems using pipelines are designed for the inch measurement system.

This is due to the fact that the non-metric system, along with all the equipment, came to us from developed countries of the world, where all industry since the 15th century was oriented towards the English inch, approximately equal to the width of the thumb of 25.4 mm. A system with a basic dimensional unit of 1 meter, which appeared much later in the 19th century, is used everywhere, but was never able to displace inches from the measurements of equipment elements, gas and water mains.

This happened partly because counting tenths of millimeters is too inconvenient and accuracy suffers, while threaded elements of half an inch, three-quarters, one and a half, and so on are easier to designate and produce. In the manufacture of household plumbing, the standard inch pitch is 1/4″ - this is 6 times more than a millimeter and allows you to significantly reduce the number of standard sizes of connecting pipes for plumbing fittings.

Fig.2 Cylindrical profile and its dimensions

Thread parameters

Any thread is determined by the following indicators:

• Outside diameter. Corresponds to the distance from the tops of the ridges on different sides and is equal to the circumference of the cylinder on which the cutting is made.
• Inner diameter. The distance between the depressions of diametrically located profile ridges.
• Step or move. The distance between the vertices of the thread profile. In pipe knurling, it is measured in turns per inch.
• Profile angle. The angle of the tapered ridge, measured in degrees.
• Depth. The height of the ridge from the top to its base.

Pipe threads used in everyday life

Domestic GOSTs regulate two main types of pipe threads: conical and cylindrical, the main difference of which is the profile of the workpiece. In the first case, it is conical in shape (taper 1 to 16); in the second type, the base is a cylindrical blank.

Source: https://montagtrub.ru/otlichie-rezbyi-metricheskoy-ot-trubnoy-parametryi/

Pipe thread - types, sizes, table

A thread is a spiral with a constant pitch, cut onto a cylindrical or conical surface. Some people have a strong opinion that pipe and inch threads are the same thing, but this is fundamentally wrong. Pipe thread sizes are not diameters in mm or inches, but rather a number that indicates the bore diameter of a standard pipe.

Pipe thread is one of the most reliable methods for creating detachable pipe connections in water supply and gas supply systems.

The thread is obtained by forming a spiral-shaped channel on the outer or inner surface of the pipe.

Threads of this class are produced either by cutting or rolling. The thread groove obtained by any of the above methods must meet all the requirements of the standards.

On the territory of our country, GOST 6357-73 “Cylindrical pipe thread” is in force.

Types of pipe threads and their characteristics

Existing regulatory documents allow the use of the following types of threads:

• cylindrical;
• conical;
• inch.

The first type is a spiral cut, formed by a triangular cross-section with an apex angle of 55 degrees.

The second type is a cut similar to the previous one on a beveled section of pipe equal to 1/16.

The third type is a thread whose profile is a cross-section in the shape of an isosceles triangle with an apex angle of 55 degrees.

In some countries, such as the USA or Canada, the apex angle is 60 degrees. In fairness, it should be noted that the latter type of thread is gradually going out of circulation.

In pipeline connections, cylindrical or conical pipe threads are most often used. The cylindrical type is designated “G”, the letters “R” and “K” indicate the presence of a tapered thread. The characteristics of metric knurling are regulated in GOST 8724-81, metric conical knurling is standardized in GOST 25229-82, and for tapered inch threads GOST 6357-81 applies.

Step Definition

To establish the thread and its pitch, a measuring tool called a thread gauge is used. It is acceptable to use a metal ruler or a caliper tool, in this case a caliper. There is also a “folk” method of measuring step. But it is advisable to use it only when you don’t have a special measuring tool at hand.

To implement the “folk” method, you need to roll the end of the pipe over a sheet of paper and count the number of prints at a distance of one inch, the result will be the number of turns. To measure using a thread gauge, you will need to go through several templates and the one that does not leave a gap between the pipe body and the sample will be the required size. The name of the thread is engraved on the template.

Pipe cylindrical thread

Cylindrical pipe thread is a detachable connection consisting of spiral grooves cut inside and outside of parts. This type of thread is used for the installation of pipes, fittings, shut-off and control valves, as well as other pipeline structural elements. The thread has a triangular cross-section with an apex angle of 55°.

Features of pipe thread

Pipe threads differ from standard metric threads by a sharper triangle apex (55° versus 60°) and slightly rounded tooth tips. This ensures maximum density and tightness of the pipe connection, which plays a special role when installing pipelines.

The main parameter of a thread is its outer diameter, measured in so-called. pipe inches (1 inch equals 33.24 mm) consisting of the sum of the internal diameter and the thickness of the outer walls. The current standards define the following connection parameters:

• The largest pipe diameter is 6 inches. For larger values, a welded connection is used.
• The thread pitch consists of 4 standard sizes. Thread counts are 11, 14, 19 and 29 per standard inch.
• There are two rows of outer diameters. When choosing a diameter, preference is given to the first row.
• The international designation indicates the symbol G (Tr. according to GOST 6357-81), size and accuracy class. When executed on the left, the letters LH are added. Also, at the end, the length of the threaded connection can be indicated.

This type of detachable connection is manufactured at the factory by knurling, taking into account the wall thickness and outer size of the product. This allows you to get the most durable and tight connection. Moreover, unlike metric threads, the presence of each standard diameter with its own pitch increases the reliability of the connection.

Connection parameters

The minimum pipe thread diameter is 1/16″, which corresponds to 7.72 mm, the maximum is 6″ or 163.8 mm. There are 16 standard sizes in total, depending on the outer diameter of the connection, which is measured along the upper ridges. The internal diameter is determined by the lowest points at the opposite ends of the ridge.

Another leading characteristic is the cutting pitch, which is determined by the distance between adjacent thread crests or valleys. The pitch is the same on any section of the connection and is measured by the number of turns per technical inch equal to 25.4 mm. This characteristic also depends on the profile height and is equal to half the difference between the internal and external diameters.  

Cutting methods and control methods

Pipe thread cutting can be done manually using dies and taps, as well as on screw-cutting lathes and special thread-rolling machines.

The manual cutting method is no different from preparing metric threads - a die with a knob is put on a fixed pipe and rotated clockwise.

For high-quality cutting, it is necessary to use lubricants and alternate several working rotations with a reverse movement to remove chips. Tapping is done in the same way.

For mass production, a mechanical method is used on semi-automatic lathes and CNC. Cutting is carried out with special cutters or using dies. In the factory production of pipes with ready-made threaded connections, the method of hot or cold rolling with special rollers is used. To determine the thread parameter, gauges or flat templates are used.

GOST

The parameters of cylindrical pipe threads are determined by GOST 6357-81. It is based on the Whitworth fine thread standard and is compatible with the European BSP standard.

Source: https://mekkain.ru/stati/trubnaya-czilindricheskaya-rezba.html

Plumbing thread. Table. Types | Construction Bulletin

A thread as such is a sequence of helical grooves with a constant cross-section and pitch, which are applied to cylindrical or conical surfaces. Threads are used to make threaded connections for pipes for various purposes.

The thread is characterized by such indicators as:

• Diameter units
• Location
• Profile of thread-forming surface
• Direction
• Number of thread starts

Pipe thread is a fairly separate group of standards that regulate connection parameters using pipes made of various materials. Below we will look at several types of pipe threads.

Straight pipe thread

Cylindrical pipe thread Also known as Whitward thread. (British Standard Whitworth). This type of thread is used for cylindrical threaded connections, as well as for connecting internal cylindrical and external conical pipe threads.

Straight thread

The parameters of this type of thread are as follows:

• Designation of the profile shape - inch thread (thread profile in the shape of an isosceles triangle with an upper angle of 55 degrees)
• The largest pipe diameter for a threaded connection is 6 inches

Note!

A welded connection should be used to connect pipes larger than 6 inches in diameter.

Tapered pipe thread

Threads of this type are used for pipe conical connections, as well as for joining internal cylindrical threads with external conical threads.

In this case, the sealing function is performed by the thread itself, and the use of sealant is mandatory.

Tapered thread

Thread characteristics:

• Inch thread with taper
• The letter index of the thread does not indicate its type (R - external thread and Rc - internal thread, LH - left-hand thread)

Round thread (for sanitary fittings)

Round threads for plumbing fittings are used where it is necessary to arrange frequently detachable connections. Thanks to its design features, this type of thread is characterized by a long service life and high resistance to loads (even very significant ones).

Round threads are used in such elements as:

• Faucets
• Cranes
• Valves
• Spindles

It is allowed to use this type of thread in elements that operate in a polluted environment.

Circular thread pattern

Source: https://svestnik.kz/rezba-santehnicheskaja-tablica-vidy/

Pipe thread sizes, GOST inch threads, indicators and features

At first glance, it seems that there is nothing complicated in creating a pipe. You just need to connect and twist the individual parts.

But in the case when you do not have a special technical and engineering education with a specialized specialty, then some questions will necessarily arise during your work, for the answers to which you should go to a professional. But in most cases, users immediately go to look at information on the Internet.

It was previously stated that there are different diameters of metal pipes. Today it is worth trying to bring greater clarity to the threaded connections of pipes for various applications. You should try not to clutter the article with a large number of definitions. Basic terminology can be considered in GOST 11708−82, which you can familiarize yourself with.

Pipe cylindrical thread

1. The unit of measurement of parameters is inch.
2. The direction will be left.
3. Accuracy class: Class A in this case is increased, and class B is average.

Why is the measurement done in inches?

Inch sizes came to us from Western manufacturers, since the requirements of the GOST current in the post-Soviet space are formulated on the basis of a special BSW thread (British Standard Whitworth or Whitworth thread). Design engineer Joseph Fittworth (1803−1887) invented and demonstrated the same screw profile for detachable type connections back in 1841, and demonstrated it as completely universal, reliable, and also comfortable to use.

This type of threading is used both in simple pipes and in their elements and connections : locknuts, couplings, elbows, tees.

In the cross-section of the profile, you can see an isosceles triangle with a total angle of 55 degrees and roundings at the tops and in the valleys of the contour themselves, which are used for a higher sealed connection.

Threading of threaded connections should be carried out on sizes up to 6 . All pipes are created large; for special reliability and to prevent pipe rupture, the joints should be fixed with additional welding.

Symbols in the standard.

1. International: G.
2. Japan: PF.
3. England: BSPP.

The letter G indications, as well as the bore diameter, will be given in inches. The outer diameter of the thread itself cannot be found in the designation.

Pipe thread sizes, inch

G ½ - pipes in the form of an external cylinder, the internal diameter of the hole is ½. The outer diameter of such a pipe will be 20.995 mm, the number of steps along the length will be 25.4 mm, which means about 14 steps.

For example:

1. G ½ -B—cylindrical pipe thread, internal hole diameter ½ inch, pipe accuracy class coincides with mark B.
2. G1 ½ LH-B—cylindrical pipe, internal hole diameter up to ½, accuracy class B, left.

For an internal cylindrical pipe, it is worth using a hole that will fully comply with the parameters.

How to quickly find a pitch in a pipe

You can consider additional photographs from English-language sites that can clearly demonstrate the methodology for using and constructing the structure. Pipe threads are characterized in most cases not by the total size between the tops of the profile, but by the number of total turns per 1 inch along the entire axis of the surface. Using a simple tape measure and a ruler, apply and measure one inch (25.4 mm) and visually calculate the number of steps.

It will be much easier if you have an inch thread gauge in your toolbox. With such a device it is quite easy to carry out all measurements, but it is worth remembering that the threads can differ in the angles of the vertices - 55 and 60 degrees.

Tapered pipe thread GOST 6211081

The unit of measurement for all parameters in this case is inch.

The shape of such a pipe will correspond to the profile of a cylindrical pipe cut with a total angle of 55 degrees Celsius.

Main designations:

1. International - R
2. Japan - PT.
3. UK BSPT.

To do this, it is worth indicating the letter R and the overall nominal diameter Dy. The designation in the form of a letter characterizes the external type of thread, Rc is internal, and Rp is internal cylindrical. In the same way with a cylindrical pipe, LH should be used for left-hand threads.

Examples:

R1 ½ is a tapered cut outer pipe with a nominal diameter of Dy ½ inch.

R1 ½ LH is an outer tapered pipe whose nominal diameter Dy will be ½ inch.

1. Inch conical cutting according to GOST 6111−52.
2. The unit of measurement in this case is also inches.
3. It is manufactured on a surface with a taper of 1:16.

It has a general profile angle of about 60 degrees. It is used in the manufacture of pipelines (water, air, and fuel) for machines and machines with low pressure during operation. The use of this type of connection includes special tightness and locking of the thread without the influence of additional improvised means (linen threads, as well as yarn with red lead).

Main designations

The first letter in the name is K, and after that comes the word GOST.

Example: K: ½ GOST 6111–52.

This inscription is deciphered as follows: an inch conical thread with an outer and inner diameter in the main plane approximately equal to the outer or inner connector of a cylindrical pipe G ½.

Metrically conical cut type. According to GOST 25229 -82.

The unit of measurement this time is mm.

The process of creating a pipe occurs on surfaces with a total taper of 1:16.

Used when connecting pipelines. The angle at the very top of the coil will reach 60. The plane is shifted when looking at the end.

Main parameters for the pipe

The regulatory document that describes the mandatory requirements for the dimensions of cylindrical threads is considered to be GOST 6111–52. Like other varieties, an inch cut includes two main characteristics: diameter and pitch. According to the latter, it is worth understanding the following features:

1. The outside diameter, which is measured between the highest point in the threaded flange located on the opposite side of the pipe.
2. Internal diameter as a value that characterizes the total distance from one of the lowest points of the cavity between the threaded ridges and to the second, also located at the opposite end of the pipe.

If you remember the outer and inner diameters of the inch thread, you can easily calculate the height of its profile. To calculate this parameter, it is enough to determine the total difference between two such diameters.

The second important parameter will be the step, which characterizes the distance at which two adjacent ridges or two adjacent depressions stand from each other. Throughout the entire section of such a product on which the pipe thread is made, its pitch does not begin to change and has the same general value. If such a requirement is not met, then it will become inoperative, and it will be impossible to select a second element of the structure being created for it.

Main differences from metric threads

In terms of their external characteristics and features, both inch and metric threads do not have so many differences; the most significant ones include:

1. how to calculate step parameters;
2. general shape of the ridge (its profile).

When comparing the type of threaded ridges, you can easily see that the inch type has sharper elements, unlike the metric type. If we consider the exact dimensions, then at the top of the inch thread there will be an angle equal to 55 degrees.

The parameters of metric as well as inch cuttings are described by various measurement indicators. So, the diameter and pitch of the former are measured in millimeters, and the latter, respectively, in inches.

It should also be borne in mind that in relation to the inch cut, not the generally accepted one (2.54 cm) is used, but a special pipe inch, which will reach up to 3.324 cm.

Thus, if, for example, its total diameter is ¾ inches, then in terms of millimeters it will be equal to the value 25.

To calculate the main parameters of an inch cut for any size that is fixed by the official GOST, you just need to look at a specialized table . In tables containing inch thread sizes, both whole and fractional indicators are given. It is worth remembering that the pitch in such tables is used in the form of cut grooves (threads), which include one inch of the length of the entire product.

To understand whether the pitch of the resulting thread corresponds to the dimensions specified by GOST itself, this parameter should be measured qualitatively. For this type of measurement, which can be carried out for both metric and inch, threading is carried out according to the same principle, standard tools are used: gauge, mechanical meters, and also a comb.

The easiest way to measure an inch thread is in the following ways:

1. As a simple method, it is worth using a coupling or fitting, the internal cutting parameter of which fully complies with all the standards given by GOST itself.
2. A bolt, the general parameters of the external thread of which should be completely measured, an additional coupling or fitting is screwed in.
3. If the bolt itself has created a complete threaded connection with the coupling or fitting, then the overall diameter and pitch of the thread that was applied to its parts will fully comply with all the parameters of the template used.
4. The pitch of an inch thread is the number of threads per inch.

In the case when the bolt is not screwed into a simple template or is screwed in. But at the same time it creates a poor-quality connection with it, then you need to take measurements using a simple coupling or another type of fitting. Using a similar method, it is worth measuring the internal thread in a pipe; only in such cases it is worth using a product with an external thread as a special template.

To determine the required dimensional requirements, it is worth using a thread gauge , which looks like a plate with special notches, the shape and other characteristics of which will fully correspond to all parameters of the thread with pitch measurement.

This type of plate, which acts as a special template, simply needs to be applied to the thread being tested with the jagged side.

The fact that the cut on the element meets all the parameters and is executed correctly will be indicated by a tight fit of the jagged part of the plate to its profile.

To measure the outer diameter of an inch or metric thread, you should use a simple micrometer or caliper.

Cylindrical pipe threads, which are classified as inch threads (both internal and external), can be cut either mechanically or manually.

The process of cutting threads using a hand tool , which should be a tap (for internal) or a die (for external), is used in several steps at once.

1. The tube being processed must be clamped in a vice, and the tool used should be fixed in a driver (tap) or die holder (die).
2. The die should be put on one end of the pipe, and the tap should be inserted into the inner part.
3. The tool used is screwed into the pipe or screwed onto it at one end using a special rotation of the driver or die holder.
4. To ensure the cleanest and highest quality result, it is worth carrying out the cutting procedure into several parts.

Symbols for inch pipes

In this marking you can find information about the thread such as:

1. Group.
2. Accuracy classification.
3. The nominal size (that is, the outer diameter of the pipe) is the first few numbers.
4. The number of turns that fall on one inch of length.

Source: https://tokar.guru/truby/trubnaya-rezba-glavnye-parametry-i-oboznacheniya-osobye-metodiki.html

Pipe thread

Connecting sections of water and gas pipes using threaded connections is a reliable and convenient way.

To do this, a recess in the form of a spiral with a constant depth and a constant distance between adjacent grooves is created on the outer surface of the pipe and on the outer or inner surface of the connecting pipe of the shut-off valve or fitting.

In order for the connection to be durable and not leak, the threaded profiles on the parts being connected must match in their parameters. In everyday life, during the construction of private houses and renovation of apartments, cylindrical inch pipe threads of ¼, ½ and 1 inch have become the international standard.

Pipe thread

Pipe thread sizes. Designation. GOST standards

It would seem that there is something complicated in the pipes? Connect and twist But, if you are not a plumber or an engineer with a specialized education, then you will definitely have questions for answers to which you will have to go wherever you look. And most likely the first thing they look at is the Internet)

We have previously talked about the diameters of metal pipes in this material. Today we will try to clarify the threaded connections of pipes for various purposes. We tried not to clutter the article with definitions. The basic terminology is contained in GOST 11708-82, which everyone can familiarize themselves with.

Pipe cylindrical thread. GOST 6357 - 81

Parameter Unit: Inch

Direction: Left

Accuracy class: Class A (increased), Class B (normal)

The inch size came to us from our Western colleagues, since the requirements of the GOST are formulated on the basis of BSW (British Standard Whitworth or Whitworth thread). Joseph Whitworth (1803 - 1887), a design engineer and inventor, demonstrated the screw profile of the same name for detachable connections back in 1841 and positioned it as a universal, reliable and convenient standard.

This type of thread is used both in the pipes themselves and in the elements of pipe connections: locknuts, couplings, elbows, tees ( see picture above ). In the profile section we see an isosceles triangle with an angle of 55 degrees and roundings at the tops and bottoms of the contour, which are made for high tightness of the connection.

Threading of threaded connections is carried out on sizes up to 6”. All larger pipes are fixed by welding to ensure a reliable connection and prevent rupture.

Symbol in the international standard

International: G

Japan: PF

UK: BSPP

The letter G and the bore diameter (internal Ø) of the pipe are indicated in inches. The outer diameter of the thread itself is not included in the designation.

Example:

G 1/2

Source: http://bydom.ru/news/read/Razmery-trubnoy-rezby.html

Types and sizes of pipe threads - characteristics, norms, standards

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Any master working in the field of plumbing should be familiar with pipe threads and its varieties. Standard pipe threads have certain parameters collected in a single table. When carrying out work on the installation of plumbing equipment, it is important to adhere to established standards. Otherwise, the resulting poor-quality connection may lead to malfunctions in the pipeline.

Types of threaded notches

Threaded notches are rows of notches arranged in a spiral. The application of helical relief can be performed on elements in the shape of a cylinder or cone. In this case, the same pitch and diameter must be maintained throughout. This thread is used to create screw connections. The main areas of use are automotive and communication systems.

Helical relief can be of two types:

Pipe notching is considered a separate type. It is made on elements made of metal and polymer materials. Most often, pipe notches are used when assembling domestic systems, such as water supply and heating.

Types of pipe threads and sizes

The carving is assessed according to several criteria:

• Direction and location.
• Profile elements, here we are talking about protrusions and recesses, which are clearly visible in the longitudinal section.
• The value taken as a unit of measurement for profile elements. Pipe thread sizes are measured in mm or inches.
• Internal diameter. This value is measured differently for different parts: on bolts - along the relief grooves, on nuts - along the external profile.
• The thread pitch determines the distance between two adjacent threads located in parallel.

Upon inspection, it is quite difficult to determine the type and dimensions of the pipe thread. A caliper is used for this purpose. And the parameters obtained as a result of the measurements are compared with tabular data.

Inch and metric pipe threads have different sizes. The main determining parameter is the cross section. Moreover, the metric thread is determined by the pipe diameter and pitch. Inch cutting is characterized by the number of turns per inch or fraction of an inch. However, it is worth considering that compared to the standard inch, which is 2.54 cm, the pipe inch has a difference and is equal to 3.324 cm.

Source: https://trubaspec.com/soedinenie-trub/vidy-i-razmery-trubnoy-rezby-kharakteristiki-normy-standarty.html

Detailed table of pipe thread sizes with inches and mm

The joining of individual elements of pipeline fittings for water supply and gas lines is carried out using a threaded connection. Such a joint provides a strong and reliable unit, guaranteeing the durability and tightness of the entire utility network.

The proposed review article contains complete information about popular types of connections used in everyday life and repair and construction work. Any home craftsman or amateur plumber, after reading the article, will receive comprehensive answers to all questions about pipe threads.

Existing thread cutting methods

Pipe threads are applied in the following ways:

1. For cutting internal and external profiles, special metalworking tools - taps and dies - are used. This cutting method is often used by amateur plumbers in self-installation of household pipelines.
2. Cutting using the knurling method is used for metal water and gas pipes with a diameter of 10 mm - 65 mm. The resulting profile is characterized by high accuracy.
3. The workpiece is processed with special cutters on lathes. Using this method, pipe threads of any diameter are applied.

The first two methods are most often used in household utilities, the third is used in the construction of industrial pipelines.

Pipe thread classification parameters

Threaded connections are classified according to different parameters. According to the cutting method, they can be grouped into the following types:

1. The type of groove surface is in the form of a cylinder (cylindrical) or a cone (conical).
2. Location on the product. Cut along the outer or inner surface.
3. Number of entries of spiral recesses. There can be single-pass and multi-pass.
4. Knurling profile. It can be a rectangle, triangle or trapezoid. Most often, a triangular profile is used as the most durable for universal use.
5. Direction of turns. Can be rectangular or left-handed.
6. Unit of measurement of diameters. Threaded connections are measured in metric or inch systems.
7. Purpose. They can be fastening, running, fastening-sealing and thrust.

Pipe threads used in the installation of water supply systems, heating networks and sewerage systems are divided into the following types:

• Cylindrical.
• Conical.
• Inch.

The area of ​​application of each type of profile is specified by its technical properties and characteristics.

Conical

A pipe profile with a thread in the form of a reduced cone is called a tapered thread.

In drawings and installation diagrams it is designated by the English letter G and measured in inches. This type of cutting is used to seal high-pressure pipelines filled with liquids or gaseous substances. Conical knurling provides a strong monolithic connection of products.

An example is the hydraulic drive of heavy equipment, in which an oily fluid operates under high pressure conditions. In this case, profiles of different types are involved in connecting nodes. Therefore, tapered threaded connections are indicated by an indicator in the form of a fraction, where the numerator is the internal thread, and the external thread is shown in the denominator.

Round metric

Plumbing fittings are subject to high requirements for tightness and detachability of connections.

The design features of round metric threads provide high resistance to external and internal forces, which significantly increases the service life of the entire assembly.

The profile in appearance resembles a circle, with peaks and valleys connected at an angle of 90 degrees.

The following elements are equipped with round threads:

• Cold and hot water mixers.
• Plumbing taps.
• Shut-off valves.
• Spindles.

Round cuts can be used in parts and elements used in polluted environments.

National pipe thread - NPT

NPT (National Pipe Thread) standards are marked when purchasing plumbing fixtures and products made in America. The NPT thread complies with GOST No. 6111.1952. Despite its age, this standard is used in almost all CIS countries. This document describes an inch tapered thread with a 60 degree profile.

NPT threads are available in sizes from 1/16" to 24". It should be noted that this marking indicates the flow section of the pipe cavity, and not the usual meter - the outer diameters of the connected pipes or fittings.

Table of the main sizes of tapered inch threads according to the NPT and GOST 6111.

Size(inches)	Intermediate diameter(mm)	Length(mm)	Number of turns
1/2	19,78	13,5	14
1/16	7,142	6,5	27
2	58,33	19	11,5
1/8	9,52	7	27
3/4	25,12	14	14
1 1/2	46,3	18,5	11,5
1/4	12,45	9,5	18

Main types and their differences

A metric profile differs from a pipe thread in the shape of the threaded crests and valleys.

1. The basis of metric thread is a triangle with equal sides. Therefore, all angular dimensions are the same and amount to 60 degrees. For inch pipe profiles, the angle dimensions are 55 degrees.
2. Metric is measured in mm, tubular - in inches.
3. When cutting a pipe profile, the thickness of the walls of the pipe section is taken into account.
4. Threads with a metric profile are marked with the letter “M”, the range is from 1.0 mm to 600 mm
5. The pitch of metric thread turns is 0.075 – 3.5 mm. The minimum cutting pitch is used in measuring instruments, the average profile pitch is used in parts and assemblies operated in areas of high vibration.

Large metric cutting is involved in the creation of load-bearing heavy structures.

Symbols for inch threads in international standards

In almost all countries, the universal inch measurement system is used to mark threaded connections of pipelines and connecting fittings.

In regulatory GOSTs, reference tables, and calculation formulas, a single symbol for inches is adopted in the form of a number with one or two strokes on the right. This icon is understandable to specialists from all countries and allows them to quickly navigate technical documentation and diagrams. For example, if you need a cut with a size of three inches, the production order will be marked 3″

Dimensions of runs, undercuts, grooves

List of main structural elements of external pipe threads:

• Escape.
• Undercut.
• Inflow.
• Chamfer.

Schematic representation of the main structural elements

Table of main structural elements:

Tables of main parameters of tapered inch threads

The profile and standards of the DKR with a profile angle of 60° must comply with the drawings. 1 and table.

The standard for tapered inch threads is presented in GOST 62811-81.

Parallel Pipe Thread Size Tables

In drawings and diagrams, a cylindrical pipe is designated by the letter indicator G, the size and direction of the profile, as well as the accuracy class. For example, the thread designation j 1/2″ A stands for “half-inch cylindrical thread with accuracy class A.”

Inch thread: size table, markings, GOST

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.

Plumbing products with inch pipe threads

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:

• outer diameter, measured between the top points of the 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.

Inch thread parameters

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.

The second important parameter - the pitch - characterizes the distance at which two adjacent ridges or two adjacent depressions are located from each other. Throughout the entire section of the product on which the pipe thread is made, its pitch 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.

You can familiarize yourself with the provisions of GOST regarding inch threads by downloading the document in pdf format from the link below.
GOST 6111-52 Conical inch thread with a profile angle of 60° Download

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 of metric and various varieties of inch threads in the range of approximately Ø8-64mm

Differences from metric threads

In terms of their external features 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.

Differences in thread profile

When comparing the shapes of threaded ridges, you can see that in inch threads such elements are sharper than in metric threads. If we talk about exact dimensions, the angle at the top of the ridge of an inch thread 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.

Drawing. Main profile parameters according to GOST

Table 1. Main thread profile dimensions

Table 2. Basic parameters of pipe threads

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, a coupling or fitting is used, the internal thread parameters of 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.

Inch thread pitch is the number of threads per inch

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 in such cases a product with an external thread is used as a template.

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.

Using a thread gauge for inch threads

To measure the outside diameter of an 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

Cutting a thread using a hand tool, which uses a tap (for internal) or a die (for external), is performed in several steps.

1. 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).
2. The die is put on the end of the pipe, and the tap is inserted into the inside of the latter.
3. The tool used is screwed into the pipe or screwed onto its end by rotating a driver or die holder.
4. 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:

1. The pipe being processed is clamped in the machine chuck, on the support of which a thread-cutting tool is fixed.
2. At the end of the pipe, using a cutter, a chamfer is removed, after which the speed of movement of the caliper is adjusted.
3. 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 a lathe only on tubular products whose thickness and rigidity allow this to be done. Making pipe inch threads mechanically allows you to obtain a high-quality result, but the use of such technology requires the turner to have the 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.

Maximum size deviations according to GOST

To understand what parameters a specific threaded element corresponds to, it is enough to understand the designation of the thread that is applied to it. The designation in question is used by many foreign manufacturers who work according to American standards relating to elements of threaded connections.

An example of a symbol for an inch thread

This marking contains the following information about the thread:

• nominal size (outer diameter) – first digits;
• number of turns per inch of length;
• group;
• accuracy class.

The designation of an inch thread may also contain the letters LH, which indicate that its turns are not right-handed, but left-handed.

Source: http://met-all.org/metalloprokat/metizy/dyujmovaya-rezba-razmery-tablitsa-gost.html

Machine parts



Connecting parts using threads is one of the oldest and most common types of detachable connections. Easy and simple to assemble and disassemble. A threaded connection is formed by two parts.

One of them has protrusions located on the screw surface on the outer surface and the other on the inner surface - respectively, external and internal threads.
Threads are formed on cylindrical or conical surfaces.

The most common are cylindrical threads.

Threads are classified according to various criteria:

In the direction of the helix: right, left.

By profile shape: triangular, trapezoidal, rectangular, round, thrust, metric, inch.
By location on the part: external, internal.
By the nature of the surface: cylindrical, conical.
By purpose: fastening, fastening and sealing, chassis (for transmitting movement), special (including: clock, on plastic parts, eyepiece, round for microscope lenses, round for lighting equipment).
By number of passes: single-pass, multi-pass.

***

Metric thread

Metric thread (Fig. 1, a) is the main type of fastening thread.
The thread profile is established by GOST 9150–81 and is an equilateral triangle with a profile angle α = 60°. The thread profile on the rod differs from the thread profile in the hole in the amount of blunting of its peaks and valleys.

The main parameters of a metric thread are: nominal diameter - d(D) and thread pitch - P, established by GOST 8724–81 in millimeters.

Metric threads come in coarse and fine pitch. For each thread size (diameter), the standard establishes a nominal pitch. If the thread on a product has a pitch less than the nominal one, then such a thread is considered small; if the pitch is larger than the nominal one, the thread is large.

According to GOST 8724–81, each nominal thread size with a large pitch corresponds to several small steps.

Fine-pitch threads are used in thin-walled connections to increase their tightness, to carry out adjustments in precision mechanics and optics devices, to increase the resistance of parts to self-unscrewing.

If the diameters and pitches of threads cannot satisfy the functional and design requirements, ST SEV 183–75 “Metric threads for instrument making” was introduced.
If several step values ​​correspond to one diameter, then the larger steps are used first. The diameters and pitches of threads indicated in brackets are not used if possible.

In the case of using a conical metric thread (Fig. 1, g) with a taper of 1:16, the thread profile, diameters, pitches and main dimensions are established by GOST 25229–82.
When connecting an external conical thread with an internal cylindrical thread in accordance with GOST 9150–81, it must be ensured that the external conical thread is screwed in to a depth of at least 0.8d.

Inch thread

Inch thread (Fig. 1, b) refers to the fastening 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. In the CIS, it is used only for threaded parts of old and imported machines (China, USA, etc.).

Inch thread is characterized by the fact that it has a triangular profile with an angle α = 55°, and the diameter is measured in inches, the pitch is the number of threads per length of 1”.
This thread was standardized for outer diameters d = 3/16” - 4” and the number of threads per 1” from 28 to 3. When designating an inch thread, the outer diameter is indicated in inches.

Pipe tapered thread

Tapered pipe threads (Fig. 1, h) are used as fastening and sealing threads.
The parameters and dimensions of conical pipe threads are determined by GOST 6211–81, according to which the thread profile corresponds to the profile of an inch thread.
The thread is standardized for diameters from 1/16” to 6” (in the main plane, the thread dimensions correspond to the dimensions of a cylindrical pipe thread).

Source: http://kat.ru/detali_mashin/9-dm_pezba/

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