Very often on the packaging (box) with a mixer, in the list of product characteristics, you can see the number 3/8 inch in the “connecting size” column.

What size is this, and how will we connect the mixer if we purchase it?

Connecting size 3/8 inch, corresponds to M10 metric thread. These are the dimensions of the threaded connection of the fitting part of the flexible liner. On one side of such a hose, covered in a metal braid, there is a 10 or 11 millimeter turnkey fitting and a thread at the end of 10 millimeters, or 9.5 millimeters, which corresponds to three-eighths of an inch.

This is what they look like.

First, a short fitting is screwed to the mixer, then a long one. This is so that the edges of the fittings and the thickening of the crimping do not interfere with each other.

Eat Alternative option for reinforced flexible connections these are bellows hoses for mixers. They are not much more expensive, but their service life is many times greater than the service life of a braided rubber hose. So if it's ordinary flexible liner serves 3-4 years, then bellows up to 10 years.

At the second end, the flexible hose may have a thread instead of a nut, complete with faucets, most often there is a nut, so be aware that if there is a nut at the outlet of your pipeline, you will need to purchase a nipple -

Her Majesty the trumpet! Of course, it makes our lives better. Like that:

The key characteristic of any cylindrical pipe is its diameter. It can be internal ( Du) and external ( Dn). Pipe diameter is measured in millimeters, but the unit of pipe thread is inch.

At the junction of the metric and foreign measurement systems, the most questions usually arise.

Besides, it's real existing size internal diameter often does not coincide with Dy.

Let's take a closer look at how we can continue to live with this. A separate article is devoted to pipe threads. Read also about profile pipes, which are used for the construction of structures.

Inches vs mm. Where does the confusion come from and when is a correspondence table needed?

Pipes whose diameter is indicated in inches ( 1", 2" ) and/or fractions of inches ( 1/2", 3/4" ), are a generally accepted standard in water and water-gas supply.

What's the difficulty?

Take dimensions from the pipe diameter 1" (how to measure pipes is written below) and you will get 33.5 mm, which naturally does not coincide with the classical linear table for converting inches to mm ( 25.4 mm).

As a rule, installation of inch pipes occurs without difficulties, but when replacing them with pipes made of plastic, copper and of stainless steel a problem arises - the size of the designated inch does not match ( 33.5 mm) to its actual size ( 25.4 mm).

Usually this fact causes bewilderment, but if you look deeper into the processes occurring in the pipe, the logic of the size discrepancy becomes obvious to a layman. It's quite simple - read on.

The fact is that when creating a water flow, the key role is played not by the external, but by the internal diameter, and for this reason it is used for designation.

However, the discrepancy between designated and metric inches still remains, since the internal diameter of a standard pipe is 27.1 mm, and reinforced - 25.5 mm. The last value is quite close to equality 1""=25,4 but still he is not.

The solution is that to indicate the size of pipes, a nominal value is used, rounded to standard value diameter (nominal diameter Dy). The size of the nominal diameter is selected so that the throughput of the pipeline increases from 40 to 60% depending on the growth of the index value.

Example:

The outer diameter of the pipe system is 159 mm, pipe wall thickness 7 mm. The exact inner diameter will be D = 159 - 7*2= 145 mm. With wall thickness 5 mm size will be 149 mm. However, in both the first and second cases, the conditional passage will have the same nominal size 150 mm.

In situations with plastic pipes To solve the problem of inappropriate dimensions, transition elements are used. If it is necessary to replace or connect inch pipes with pipes made according to real metric dimensions - copper, stainless steel, aluminum, you should take into account both the external and internal diameters.

Table of nominal diameter in inches

Du	Inches	Du	Inches	Du	Inches
6	1/8"	150	6"	900	36"
8	1/4"	175	7"	1000	40"
10	3/8"	200	8"	1050	42"
15	1/2"	225	9"	1100	44"
20	3/4"	250	10"	1200	48"
25	1"	275	11"	1300	52"
32	1(1/4)"	300	12"	1400	56"
40	1(1/2)"	350	14"	1500	60"
50	2"	400	16"	1600	64"
65	2(1/2)"	450	18"	1700	68"
80	3"	500	20"	1800	72"
90	3(1/2)"	600	24"	1900	76"
100	4"	700	28"	2000	80"
125	5"	800	32"	2200	88"

Table. Inner and outer diameters. Stacked water/water-gas pipelines, epectros-welded longitudinal, seamless hot-deformed steel and polymer pipes

Table of correspondence between nominal diameter, thread and outer diameters of the pipeline in inches and mm.

Nominal pipe diameter Dy. mm	Thread diameter G". inch	Pipe outer diameter Dn. mm
		Water/water-gas pipes GOST 3263-75	Epoxy-welded straight-seam steel pipes GOST 10704-91. Seamless hot-deformed steel pipes GOST 8732-78. GOST 8731-74 (FROM 20 TO 530 ml)	Polymer pipe. PE, PP, PVC

GOST- state standard used in heat - gas - oil - pipelines

ISO- standard for designating diameters, used in plumbing engineering systems

SMS- Swedish standard for pipe diameters and valves

DIN/EN- the main European range for steel pipes according to DIN2448 / DIN2458

DU (Dy)- conditional pass

Size tables polypropylene pipes presented in the next article >>>

Conformity table for nominal pipe diameters with international markings

GOST	ISO inch	ISO mm	SMS mm	DIN mm	DU
8	1/8	10,30			5
10	1/4	13,70	6,35		8
12	3/8	17,20	9,54	12,00	10
18	1/2	21,30	12,70	18,00	15
25	3/4	26,90	19,05	23(23)	20
32	1	33,70	25,00	28,00	25
38	1 ¼	42,40	31,75	34(35)	32
45	1 ½	48,30	38,00	40,43	40
57	2	60,30	50,80	52,53	50
76	2 ½	76,10	63,50	70,00	65
89	3	88,90	76,10	84,85	80
108	4	114,30	101,60	104,00	100
133	5	139,70	129,00	129,00	125
159	6	168,30	154,00	154,00	150
219	8	219,00	204,00	204,00	200
273	10	273,00	254,00	254,00	250

Diameters and other characteristics of stainless steel pipes

Passage, mm	Diameter external, mm	Wall thickness, mm		Weight of 1 m pipe (kg)
		standard	reinforced	standard	reinforced
10	17	2.2	2.8	0.61	0.74
15	21.3	2.8	3.2	1.28	1.43
20	26.8	2.8	3.2	1.66	1.86
25	33.5	3.2	4	2.39	2.91
32	42.3	3.2	4	3.09	3.78
40	48	3.5	4	3.84	4.34
50	60	3.5	4.5	4.88	6.16
65	75.5	4	4.5	7.05	7.88
80	88.5	4	4.5	8.34	9.32
100	114	4.5	5	12.15	13.44
125	140	4.5	5.5	15.04	18.24
150	165	4.5	5.5	17.81	21.63

Did you know?

What ingenious lamps can you assemble with your own hands from ordinary metal pipe? Anyone can do this!

Which pipe is considered small - medium - large?

Even in serious sources I have seen phrases like: “We take any pipe of average diameter and...”, but no one indicates what this average diameter is.

To figure it out, you should first understand what diameter you need to focus on: it can be internal or external. The first is important when calculating the transport capacity of water or gas, and the second is important for determining the ability to withstand mechanical loads.

External diameters:

From 426 mm is considered large;

102-246 is called average;

5-102 is classified as small.

As for the internal diameter, it is better to look at the special table (see above).

How to find out the diameter of a pipe? Measure!

For some reason this strange question often comes to e-mail and I decided to supplement the material with a paragraph about measurement.

In most cases, when purchasing, it is enough to look at the label or ask the seller a question. But it happens that you need to repair one of the communication systems by replacing pipes, and initially it is not known what diameter the already installed ones have.

There are several ways to determine the diameter, but we will list only the simplest ones:

Arm yourself with a tape measure or measuring tape(women measure their waist this way). Wrap it around the pipe and record the measurement. Now, to obtain the desired characteristic, it is enough to divide the resulting figure by 3.1415 - this is the number Pi.

Example:

Let's imagine that the girth (circumference L) of your pipe is 59.2 mm. L=ΠD, resp. the diameter will be: 59.2 / 3.1415= 18.85 mm.

• After obtaining the outer diameter, you can find out the inner one. Only for this you need to know the thickness of the walls (if there is a cut, just measure with a tape measure or other device with a millimeter scale).

  Let's assume that the wall thickness is 1 mm. This figure is multiplied by 2 (if the thickness is 3 mm, then it is also multiplied by 2 in any case) and subtracted from the outer diameter (18.85- (2 x 1 mm) = 16.85 mm).

  It’s great if you have a caliper at home. The pipe is simply grabbed by the measuring teeth. We look at the required value on a double scale.

Types of steel pipes according to their production method

Electric welded (straight seam)

For their manufacture, strips or sheet steel are used, which are bent into shape using special equipment. required diameter, and then the ends are connected by welding.

The effect of electric welding guarantees a minimum seam width, which makes it possible to use them for the construction of gas or water pipelines. The metal is in most cases carbon or low alloy.

Indicators finished products are regulated by the following documents: GOST 10704-91, GOST 10705-80 GOST 10706-76.

Please note that a pipe manufactured in accordance with standard 10706-26 is distinguished by maximum strength among its peers - after creating the first connecting seam, it is strengthened by four additional ones (2 inside and 2 outside).

IN regulatory documentation The diameters of products produced by electric welding are indicated. Their size ranges from 10 to 1420 mm.

Spiral seam

The material for production is steel in rolls. The product is also characterized by the presence of a seam, but unlike the previous production method, it is wider, which means the ability to withstand high internal pressure is lower. Therefore, they are not used for the construction of gas pipeline systems.

A specific type of pipe is regulated by GOST number 8696-74 .

Seamless

Production specific type involves the deformation of specially prepared steel blanks. The deformation process can be carried out both under the influence high temperatures, and cold method (GOST 8732-78, 8731-74 and GOST 8734-75, respectively).

The absence of a seam has a positive effect on the strength characteristics - the internal pressure is evenly distributed over the walls (there are no “weak” places).

As for diameters, standards control their production with a value of up to 250 mm. When purchasing products with sizes exceeding those indicated, you have to rely only on the integrity of the manufacturer.

It is important to know!

If you want to buy the most durable material, buy seamless pipes cold molding. The absence of temperature influences has a positive effect on preserving the original characteristics of the metal.

Also, if the ability to withstand internal pressure is an important indicator, then choose round products. Profile pipes cope better with mechanical loads (they are well made from metal frames and so on.).

Here are a couple more excellent slides of creative advertising for a pipe manufacturer:

There are 2 popular sizes of structures in the construction market:

• 1\2 and 3\4 - form a separate category. due to special thread parameters (1.814), per 1 unit. measures account for 14 threads;
• within 1 - 6 inches, the pitch is reduced to 2.309, forming 11 threads, which does not affect the reduction or improvement of the quality of the connection.

One inch is 25.4 mm long, it is used to determine the internal parameters, but when laying reinforced pipes, the diameter is 33.249 mm (including the internal section and 2 walls). In assortment steel structures there is an exception - ½ inch products, where the outer section is 21.25 mm. This parameter is used when calculating the dimensions of pipes with cylindrical threads. When making calculations for pipes with a cross section of 5 inches, inner size will be 12.7 cm, and the external one will be 166.245 (reduction to 1 decimal place is allowed).

Difference between measurement systems

In terms of external parameters, inch designs do not differ from metric ones, the difference lies in the type of notches. There are 2 types of threads according to the inch system - English and American. The first option corresponds to a notch angle of 55 degrees, and the metric (American) system with an angle of 60 degrees. generally accepted.

At different degrees, it is difficult to distinguish between an angle of 55 for inch and 60 for metric designs, and the rounding of the threads is immediately visible, making it impossible for an error to occur. To measure the thread pitch, a thread gauge is used, but instead of it, a regular ruler or other device can be used well.

Replacing steel pipes with polymer ones

In the gas and water supply networks, steel products are used, the diameter of which is indicated in inches (1", 2") or fractions (1/2", 3/4"). When measuring the cross-section of a 1" pipe, the result will be 33.5 mm, which corresponds to 1" (25.4 mm). When arranging pipeline reinforcing elements, where the parameters are indicated in inches, no difficulties arise. But when installing products made of PP, copper or stainless steel instead of steel structures, it is necessary to take into account the difference in name and parameters.

To create a given flow level, the internal diameter of the pipes is taken into account. For ordinary inch pipes it is 27.1 mm, for reinforced pipes it is 25.5 mm, closest to 1". Pipelines are designated in conventional units of the flow area Du (DN). It determines the parameters of the lumen of pipes and is designated in digital values. The pitch of the nominal flow section is selected taking into account the increase in flow characteristics by 40-60% with an increase in the index. If the external cross-section and purpose of the structures are known, using a size table, the internal cross-section is determined.

In the process of connecting steel pipes with polymer structures, replacing one with another, conventional adapters are used. Dimensional discrepancies result from the use of copper, aluminum or stainless steel products manufactured according to metric standards. The actual metric dimensions of the pipes are taken into account - internal and external.

Steel pipes of the Russian Federation in comparison with the European standard

To compare the range of pipes according to GOST of the Russian Federation and European standards, the following table is used:

How to decide on the diameter?

The diameter of the water pipes determines their throughput characteristics - the volume of water passed per 1 unit. time. It depends on the speed of water flow. As it increases, the risk of pressure drop in the line increases. Flow characteristics are calculated using formulas, but when planning intra-apartment wiring, they take pipes of certain parameters.

For the plumbing system:

• 1.5 cm (1/2 inch)
• 1 cm (3/8 inch).

For the riser, structures with an internal cross section are used:

• 2.5 cm (1 inch);
• 2 cm (3/4 inch).

Considering that the internal cross-section of half-inch polymer pipes varies in the range from 11 to 13 mm, and one-inch ones - from 21 to 23, an experienced plumber will be able to determine the exact parameters when replacing. With a complex type of wiring, numerous joints, turns and network laying on long distance, reducing pressure, it is necessary to provide for the possibility of routing pipes with a large cross-section. As the diameter increases, the pressure level increases.

Below is a table for determining the permeability of steel pipes:

Steel pipe diameter

The cross-section of the pipes corresponds to a number of indicators:

• Nominal diameter (DN, Dy) – nominal parameters (in mm) of the internal cross-section of pipes or their rounded values, in inches.
• Nominal parameter (Dn Dn,).
• External size.

  The metric calculation system allows you to classify structures into small - from 5...102 mm, medium - from 102...426, large - 426 mm and more.

• Wall thickness.
• Inner diameter.

Internal cross-section for pipes with different threads corresponds to the parameters:

• 1/2 inch pipeline - 1.27 cm;
• 3/4 inch – 1.9 cm;
• 7/8 inches - 2.22 cm;
• 1 inch – 2.54 cm;
• 1.5 inches - 3.81 cm;
• 2 inches - 5.08 cm.

To determine the thread diameter, the following indicators are used:

• 1/2 inch pipeline – 2.04 - 2.07 cm;
• 3/4 inches – 2.59 - 2.62 cm;
• 7/8 inches – 2.99 - 3 cm;
• 1 inch – 3.27 - 3.3 cm;
• 1.5 inches - 4.58 - 4.62 cm;
• 2 inches – 5.79 - 5.83 cm.

Table of correspondence between the diameter of steel pipes and polymer structures:

Steel pipe prices:

PP pipe diameter

PP pipes are produced with a diameter from 0.5 to 40 cm or more. The diameter is internal and external. The first indicator allows you to find out the volume of media passed through in 1 unit. time. The external cross-section is used to carry out construction calculations, namely the selection of a niche or hole for laying a highway. External parameters allow you to choose the right fittings with the corresponding internal indicators.

• Small – 0.5; 1; 1.5; 2; 2.5; 3.2; 4; 5; 6.3 and 7.5 cm are used for heating systems, drainage and water supply in private buildings. An internal cross section of 3.2 cm is most popular in multi-story buildings.
• Average – 8; 9; 10; eleven; 12.5; 16; 20; 25 and 31.5 cm are used for arranging water supply and sewer systems, allowing you to change cast iron products with similar external parameters. The internal sizes of 8, 9 and 10 cm are ideal for chemical media.
• Large - 40 cm or more is used for arranging cold water supply and ventilation systems.

Pipes are marked in inches and mm. When choosing designs for plumbing and heating systems, the thickness of the walls is taken into account, which affects the conditional permeability of highways with the same external parameters. With an increase in its parameter, an increase in pressure is allowed in plumbing system. Small dimensions allow you to reduce the cost of purchasing material and water consumption.

Cost of PP pipes:

Video

Pipe diameter in inches and millimeters are very important indicators. Many have faced the problem of replacing or installing a pipeline, and finding the appropriate materials for the job.

In a huge number of offers construction market It’s difficult to understand, so before purchasing you should study in detail what the volume of pipe rolling is and how it is used in practice.

You can immediately use the online calculator below for translation without familiarizing yourself with the theory.

Online calculator to convert inches to millimeters and vice versa

An example of how to enter data into a calculator

When recording a size in inches, you should separate the whole part of the number from the fractional part (if any) with a space: for example, 10 1/4, or 20 4/8; otherwise it will be 101/4 and 204/8. Fractional numbers in millimeters are entered using a period rather than a comma (25.4 and not 25.4).

Enter the calculation data in the following. in order: left-click in the window of the corresponding parameter to cause a flickering cursor to appear; enter your numbers. The fractional part of an inch is entered without a sign.

1 Inch = 25.4 millimeters (mm). Currently, the inch, due to its clarity, is often used to measure the diameters of water-gas pipes and threads. Many parts also have dimensions in multiples of inches. In addition to whole inches, measurements are taken in quarters (1/4″), eighths (1/8″), sixteenths (1/16″), thirty-second (1/32″) fractions of an inch, etc.

If you have any questions about using online calculator, you can always ask a question in the form of a comment. We also strongly recommend that you read the instructions (located under the calculator).

How to convert inch values ​​to metric notations

The conversion of inches to metric indicators of pipe volumes is carried out using special tables. Here is an example of such a table:

To translate metric diameter pipe assortment must be rounded in the increasing direction. When performing this translation, you need to remember that according to international standards, one inch is taken into account as 2.54 cm.

With such data, translation can be performed using the simple calculator. Now that the cross-section of the pipe assortment has been calculated, its volume should be correctly calculated.

In practice, to convert the measurements of steel options, you need to take into account that the inch values ​​​​in the calculation will not be equal to the figure in mm. The reason is that when marking is applied, the internal volume is prescribed.

After this, the unit of measurement becomes the conditional passage, indicated by an integer. It is for these reasons that values ​​must be rounded to convert. It is difficult for an inexperienced master to make such a translation.

Therefore, if you need to translate these indicators, it is better to seek help from professionals, or carry out the translation using a special table as a basis. Professionals will help you translate required values, and will help you choose the right products and other parts for the pipeline.

Translation tables

When constructing highways for various purposes, different pipe materials are used: steel, copper, brass, plastic and others. All these products are distinguished by classification and measurement measures.

The overall dimensions of all pipe products are specified by the following indicators:

• Dn – outer Ø.
• Дв – internal Ø.
• h – wall thickness.

Previously, they used only steel lines, and for them they created their own sizing system. . These are its internal dimensions. That is, this indicator takes into account not only the size of the half-inch pipe billet, but also its capacity.

And the outer girth of a half-inch workpiece is 2.1 cm. Therefore, in the table near the floor inch thread Be sure to add the word pipes. Knowing the exact dimensions of a half-inch and any other type of assortment, you can quickly make right choice required volumes.

This is clearly visible in the table:

Dimensions (inches)	1/2	3/4	7/8	1	1,5	2
Inner Ø (metric)	12,7	19	22,2	25,4	38,1	50,8
Thread Ø (mm)	20,4-20,7	25,9-26,2	29,9-30,0	32,7 – 33,0	45,8 – 46,2	57,9 – 58,3

Nowadays it is customary to indicate these dimensions as shown in the following table provided:

First table of diameters ( its symbolic designation is Ø, which will be further denoted in the article) pipes shows values ​​in millimeters, and the second table uses inches ( international designation – inch or in, which will be further designated in the article). An inexperienced master may ask why this is? And what designations are considered correct?

The reason is that the metric system is used throughout the world. This system is based on two indicators: conditional and nominal volume. These concepts are approached in different ways, but in the end result they show external volume. At their core, these quantities are dimensionless, but sometimes they are indicated in millimeters.

By analyzing tabular data, you can compare products from domestic manufacturers and analogues foreign production.

Interesting! The discrepancy in measurements appeared simultaneously with the input copper systems in Europe in the second half of the 20th century. In Russia at that time, standards for metal assortments were determined in mm, and not in inch; this measurement system is still widely used today.

Correspondence of two notation systems

In water and gas systems Steel pipes are widely used. Their dimensions are shown in whole quantities or their fractions. For example, the diameter of a 1-inch pipe in mm will be 33.5, and the diameter of a 2-inch pipe in mm is 67.

This of course does not correspond to the stated 25.4 and 50 mm. When laying fittings with inch markings to products of 1 and 2 inch, no difficulties arise, but replacement with plastic and copper products requires taking into account the discrepancy in the markings.

Why do they make everything so complicated? The fact is that to create a fluid flow, it is important to take into account the internal size. For these reasons, this indicator began to be specified for 1-inch, 2-inch and all other pipe materials. The most accurate indicators are considered to be in nominal flow values.

The nominal bore of 1-inch, 2-inch and other pipe assortments is equal to the clearance dimensions. To indicate metric size 1 inch, 2 inch and any other pipeline, it is recommended to use tables.

Exact definitions - formula for calculation

This knowledge is needed to calculate the amount of transported medium. This is very important for heating systems. For example, when it is necessary to install a heating system, you need to determine and calculate the cross-sectional size of the assortment so that all housing is heated evenly.

How to accurately determine the cross-section of each pipe in quantities such as inches can be suggested by the formula: D = sqrt ((314∙Q)/ (V∙DT)).

• D – internal volume of rolled pipe;
• Q is the heat flow, which is determined in kW;
• V denotes the speed of the coolant, it is determined in m/s;
• DT is the difference temperature indicators, at the input and output of the network;
• sqrt – square root.

Watch the video

Despite the presence of formulas, tables help to quickly determine Ø. This is the way to win a large number of time.

What is inch volume

Decoding the pipe diameter provided in inches is simple. They are often measured in these quantities. Such one unit is equal to 3.35 cm. It has already been indicated that the interpretation of this value has discrepancies, and this is due to the fact that the assortment is measured not by the external volume, but by the internal one. For example, the internal dimensions of an inch pipe blank can vary: from 2.55 to 2.71 cm. This value varies depending on the wall thickness.

A pipe with a size of 1 inch has an outer diameter of 25.4 mm, a pipe with a size of 2 inch is equal to 50 millimeters in metric measurement. Where in technical parameters cylindrical pipe threads take the numbers 33.249 and 66.498?

This thread on 1 and 2 inch products is performed on the outer volume. Therefore, the ratio of thread diameter to internal volume is conditional. Based on this, the dimensions of 1 and 2 inch pipe products are calculated by adding the value 25, 4 or 50 with two wall thicknesses of the pipe product.

Before decoding, you need to take into account that measurements of the product should be taken not from the outside, but from the inside. Why is this necessary? The fact is that when fastening sections of the highway from different materials, and by taking measurements only from the outside, you can get an incorrect result, which will lead to an error, since the entire range differs in the dimensions of the walls.

Also, when decoding, we must not forget that the standards of different manufacturing companies are different, they all focus on their own indicators.

If it is difficult to perform such decryption on your own, then you should seek help from professionals. They will provide effective assistance when choosing the right products.

Correspondence between metric and inch parameters

All tubular products are manufactured according to a certain standard, and the pressure indicator is a fixed value. Therefore, you need to know exactly the correspondence of the Ø of all pipes shown in inches and mm. Ignoring this correspondence, it is impossible to select the correct pipe range.

Watch the video

When selecting a specific size, they are guided by the tabular information, and when replacing, we use the most approximate parameter as a guide. Exact match in two different systems There is no measurement, so pipeline elements are often equated in practice.

How this correspondence is applied in everyday life can be found in the table below:

Using this information, you can accurately determine the correspondence of two types of dimensional measurements, and take parts for work that exactly match each other.

Inch size expression

These indicators are written as a whole number, with a double stroke next to it, for example, 3“. Also, the dimensions of the pipe diameter, expressed in inches, are written as a fraction, for example, ½.

If we consider these dimensions at specific examples correspondences of Du, then they will look like this:

1. The diameter of a standard 12 inch pipe is 300.
2. The diameter of a 3 inch pipe is 80.
3. An 8 inch diameter of a standard pipe is equal to 200.
4. The diameter of a standard pipe, 32, when converted to inches is shown as 1 ¼
5. Pipe diameter 40 mm in inch is prescribed 1 ½
6. The Ø of a standard 15 inch pipe is expressed as ½
7. The Ø of a standard 4-inch product when converted to metric is 100.
8. The Ø of 3/4 inch pipe in metric conversion is 20.
9. The Ø of standard 1/2 inch pipe in metric conversion shows the number 15.

Watch the video

Pipe diameters in inches and millimeters are used constantly. Knowing these dimensions, you can avoid great difficulties when connecting pipeline elements. And special tables help you find the required dimensions of the connecting parts and adjust them correctly.

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:

• outer 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 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.

Table of sizes of inch and metric threads

Learn how metric threads relate to various types inch threads, you can use 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. However, it should be borne in mind that in relation to inch threads, not the generally accepted one (2.54 cm), but a special one is used pipe inch, equal to 3.324 cm. Thus, if, for example, its diameter is ¾ inches, 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.
• Bolt, parameters external thread which needs to be measured is screwed into the coupling or fitting.
• In the event that the bolt has formed a tight connection with the coupling or fitting threaded connection, 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 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.

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

Thread cutting using hand tools, 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 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.