5 4 inches in mm. Convert numbers from one number system to another online. Types of steel pipes according to their production method

inches	mm.	inches	mm.	inches	mm.	inches	mm.	inches	mm.
-	-	1	25,4	2	50,8	3	76,2	4	101,6
1/8	3,2	1 1/8	28,6	2 1/8	54,0	3 1/8	79,4	4 1/8	104,8
1/4	6,4	1 1/4	31,8	2 1/4	57,2	3 1/4	82,6	4 1/4	108,8
3/8	9,5	1 3/8	34,9	2 3/8	60,3	3 3/8	85,7	4 3/8	111,1
1/2	12,7	1 1/2	38,1	2 1/2	63,5	3 1/2	88,9	4 1/2	114,3
5/8	15,9	1 5/8	41,3	2 5/8	66,7	3 5/8	92,1	4 5/8	117,5
3/4	19,0	1 3/4	44,4	2 3/4	69,8	3 3/4	95,2	4 3/4	120,6
7/8	22,2	1 7/8	47,6	2 7/8	73,0	3 7/8	98,4	4 7/8	123,8

Inch thread parameters

Outer diameter of the connected pipe		SAE Thread Rating	UNF thread rating	Outer thread diameter, mm	Average thread diameter, mm	Thread pitch
mm	inch					mm	threads/inch
6	1/4""""	1/4""""	7/16""""-20	11,079	9,738	1,27	20
8	5/16""""	5/16""""	5/8""""-18	15,839	14,348	1,411	18
10	3/8""""	3/8""""	5/8""""-18	15,839	14,348	1,411	18
12	1/2""""	1/2""""	3/4""""-16	19,012	17,33	1,588	16
16	5/8""""	5/8""""	7/8""""-14	22,184	20,262	1,814	14
18	3/4""""	3/4""""	1""""-14	25,357	23,437	1,814	14
18	3/4""""	---	1""""1/16-14	26,947	25,024	1,814	14
20	7/8""""	---	1""""1/8-12	28,529	26,284	2,117	12
22	7/8""""	7/8""""	1""""1/4-12	31,704	29,459	2,117	12
22	7/8""""	---	1""""3/8-12	34,877	32,634	2,117	12
25	1""""	1""""	1""""1/2-12	38,052	35,809	2,117	12

Copper conductors, wires and cables

Conductor cross-section, mm	Copper conductors, wires and cables
	Voltage, 220 V		Voltage, 380 V
	current, A	power, kW	current, A	power, kW
1,5	19	4,1	16	10,5
2,5	27	5,9	25	16,5
4	38	8,3	30	19,8
6	46	10,1	40	26,4
10	70	15,4	50	33,0
16	85	18,7	75	49,5
25	115	25,3	90	59,4
35	135	29,7	115	75,9
50	175	38,5	145	95,7
70	215	47,3	180	118,8
95	260	57,2	220	145,2
120	300	66,0	260	171,6

Aluminum conductors, wires and cables

Cross-section of current-carrying conductor, mm	Aluminum conductors, wires and cables
	Voltage, 220 V		Voltage, 380 V
	current, A	power, kW	current, A	power, kW
1,5	19	4,1	16	10,5
2,5	27	5,9	25	16,5
4	38	8,3	30	19,8
6	46	10,1	40	26,4
10	70	15,4	50	33,0
16	85	18,7	75	49,5
25	115	25,3	90	59,4
35	135	29,7	115	75,9
50	175	38,5	145	95,7
70	215	47,3	180	118,8
95	260	57,2	220	145,2
120	300	66,0	260	171,6

Inch thread sizes

	Thread diameter in mm			Thread pitch in mm	Number of threads per 1"
	outer d	average d	internal d
3/16	4,762	4,085	3,408	1,058	24
1/4	6,350	5,537	4,724	1,270	20
5/16	7,938	7,034	6,131	1,411	18
3/8	9,525	8,509	7,492	1,588	16
1/2	12,700	11,345	9,989	2,117	12
5,8	15,875	14,397	12,918	2,309	11
3/4	19,05	17,424	15,798	2,540	10
7/8	22,225	20,418	18,611	2,822	9
1	25,400	23,367	21,334	3,175	8
1 1/8	28,575	26,252	23,929	3,629	7
1 1/4	31,750	29,427	27,104	3,629	7
1 1/2	38,100	35,39	32,679	4,233	6
1 3/4	44,450	41,198	37,945	5,080	5
2	50,800	47,186	43,572	5,644	4 1/2

Nominal thread diameter in inches
	Thread diameter in mm			Thread pitch in mm	Number of threads per 1"
	outer d	average d	internal d
1/8	9,729	9,148	8,567	0,907	28
1/4	13,158	12,302	11,446	1,337	19
3/8	16,663	15,807	14,951	1,337	19
1/2	20,956	19,794	18,632	1,814	14
5/8	22,912	21,750	20,588	1,814	14
3/4	26,442	25,281	24,119	1,814	14
7/8	30,202	29,040	27,878	1,814	14
1	33,250	31,771	30.293	2,309	11
1 1/8	37,898	36,420	34,941	2,309	11
1 1/4	41,912	40,433	38,954	2,309	11
1 3/8	44,325	32,846	41,367	2,309	11
1 1/2	47,805	46,326	44,847	2,309	11
1 3/4	53,748	52,270	50,791	2,309	11
2	59,616	58,137	56,659	2,309	11

Unit conversion table

Conversion of energy units	Conversion of pressure units
1 J = 0.24 cal	1 Pa = 1 N/m*m
1 kJ = 0.28 Wh	1 Pa = 0.102 kgf/m*m
1 W = 1 J/s	1 atm =0.101 mPa =1.013 bar
1 cal = 4.2 J	1 bar = 100 kPa = 0.987 atm
1 kcal/h = 1.163 W	1 PSI = 0.06895 bar = 0.06805 atm

Size conversion tables: simple and fast

The process of selecting the required cross-sectional sizes for threads, cables and pipes often takes a lot of time. In addition to the fact that it is necessary to select the appropriate dimensions, taking into account the parameters of the equipment, the customer has to independently convert the data into suitable units of measurement. This process requires significant time.

We simplify this task because we invite you to use ready-made translation tables. On the page of our website you will find tables that will help you easily select the necessary threads for inch pipes, copper and aluminum wires and cables. Also, you can use the table for converting inch dimensions to metric, thereby accurately calculating the required cross-sectional dimensions.

Unfortunately, most equipment manufacturers leave the customer alone with the calculations. Therefore, a person has to independently search the Internet for translation tables in order to select optimal sizes wire sections and pipe diameters.

We value the time of our clients, providing everyone with the opportunity to use ready-made solutions. Translated in our tables standard sizes from inches to millimeters.

On this page you will also find translations of basic energy units and pressure units, therefore, you will be able to choose the right refrigeration equipment, taking into account the individual placement conditions and operating modes of the units.

In Western technical literature, you will find all measurements in inch metrics. This state of affairs has historical roots. Great Britain was always ahead in terms of technical development, therefore, in all the colonies that it then owned (and there were many of them), this particular measurement system was used. In principle, technicians freely convert inches into sentiment and vice versa. To this day, in these countries, all measurements are made in inches as a standard. Next, we will talk about the main features and characteristics of inch threads and how it differs from metric threads.

Inch thread. Options

If we talk about ordinary measurement, then even in the mind it is not difficult to convert one value into another and vice versa. But as far as carving is concerned, you need to know simple, but important nuances. The fact is that there is great overlap between the metric and imperial metric for measuring lengths. The difference is the number of turns on the threaded pitch. In addition, this carving is distinguished by a different angle of inclination at its apex, which is 55°, if we refer to the Whitworth style. This is considered the norm in England, or, as they also say, the “British corner”. If we take the UNC and UNF standard, which is considered the standard in America, as a basis, then the angle here is 60°.

Metric standard and inch thread. The most fundamental differences

Types of inch threads:

• Outdoor;
• Conical;
• Cylindrical;
• Internal.

1 inch = 25.4 mm. This is the main difference. In documents this has a specific designation - 1´ (with a stroke).

If we talk about American standards, they have a division into threads with a large pitch, which they designate as UNC, and with a fine pitch, UNF. Also, for canonical inch threads the designation is NPT, and for pipe threads - NPSM.

What kind of thread is there and where is it used?

The types of threads used in production, construction and design, depending on the part, are divided into internal, external and conical.

• External is used for bolts, screws, pins and studs.
• Internal is used in the manufacture of plugs or nuts. It is cut into holes when you need to organize a connection in a certain place.
• To create a tight connection, as well as locking without additional parts, a conical inch thread is made.

Their designation follows the standard. d (D) is the outer diameter of the bolt or the inner diameter of the nut (d is the diameter of the bolt before threading). The internal diameter of the thread is designated d1 (D1). There is also a designation for the average diameter d2 (D2). This size depends on the nominal pitch, denoted by the letter P.

To indicate profile angle threads use the letter α. The indicator α = 55° will mean that the angle at the apex of the equilateral triangle of the thread tooth is 55°, and corresponds to the British Standard BSW inch thread. The UTS inch thread, widely used in Canada and the USA, has α = 60°.

Where are inch threads used?

α = 55° -inch thread used in industry for fixing mechanical components and parts using threaded connections. It is especially common during the repair of imported equipment and machines, as well as used cars. Hardware with inch thread are also produced in our country. During work, sometimes there is a need to convert metric threads to inch threads and vice versa. This can be done quickly and conveniently using a special reference book.

Threads according to the system of measures are divided into metric and inch. Metric and inch threads are used in threaded connections and screw drives. Threaded connections are detachable connections made using threaded fasteners - bolts, screws, nuts, studs or threads directly applied to the parts being connected.

Metric thread (Fig. 1)

In profile it has the appearance of an equilateral triangle with an apex angle of 60°. The tops of the projections of the mating screw and nut are cut off. A metric thread is characterized by a screw diameter in millimeters and a thread pitch in millimeters. Metric threads are made with large and small pitches. A thread with a large pitch is taken as the main one. Fine threads are used for adjustment and for screwing together thin-walled and dynamically loaded parts. Metric threads with large pitches are designated by the letter M and a number expressing the nominal diameter in millimeters, for example M20. For small metric threads, the pitch is additionally indicated, for example M20x1.5.

Rice. 1 Metric thread

Inch thread (Fig. 2)

An inch thread (Fig. 2) has the same profile as a metric thread, but its apex angle is 55° (Whitworth thread - British standard BSW (Ww) and BSF), the apex angle is 60° ( American standard UNC and UNF). The outer diameter of the thread is measured in inches (1" = 25.4 mm) - dashes (") indicate inches. This thread is characterized by the number of threads per inch. American inch threads are made with coarse (UNC) and fine (UNF) pitch.

Rice. 2 Inch thread

Fastener size chart for American inch UNC machine threads with coarse pitch (60 degree profile angle)

Size in inches	Size in mm	Thread pitch/inch
UNC No. 1	1.854	64
UNC No. 2	2.184	56
UNC No. 3	2.515	48
UNC No. 4	2.845	40
UNC No. 5	3.175	40
UNC No. 6	3.505	32
UNC No. 8	4.166	32
UNC No. 10	4.826	24
UNC No. 12	5.486	24
UNC 1/4	6.35	20
UNC 5/16	7.938	18
UNC 3/8	9.525	16
UNC 7/16	11.11	14
UNC 1/2	12.7	13
UNC 9/16	14.29	12
UNC 5/8	15.88	11
UNC 3/4	19.05	10
UNC 7/8	22.23	9
UNC 1"	25.4	8
UNC 1 1/8	28.58	7
UNC 1 1/4	31.75	7
UNC 1 1/2	34.93	6
UNC 1 3/8	38.1	6
UNC 1 3/4	44.45	5
UNC 2"	50.8	4 1/2

Thread

The thread can be internal or external.

• External threads are cut on bolts, studs, screws, pins and various other cylindrical parts;
• Internal threads are cut in fittings, nuts, flanges, plugs, machine parts and metal structures.

Rice. 3 Thread elements

The main thread elements are shown in Fig. 3 These include the following elements:

• thread pitch- the distance between the tops or bases of two adjacent turns;
• thread depth- the distance from the top of the thread to its base;
• thread angle- the angle between the sides of the profile in the plane of the axis;
• O.D. - largest diameter bolt thread, measured along the top of the thread perpendicular to the axis of the thread;
• internal diameter- a distance equal to the diameter of the cylinder on which the thread is screwed.

More about inch fasteners:

There are three thread systems used in mechanical engineering: metric, inch and pipe.

Metric thread(Fig. 145, a) has a triangular profile with an apex of 60°.

Rice. 145. Thread systems: a - metric, b - inch, c - pipe

There are six types of metric threads: main and minor -1; 2; 3; 4th and 5th. Small threads differ in pitch size for a given diameter, expressed in millimeters. Metric threads are designated by the letter M and numbers characterizing the dimensions of the outer diameter and pitch. For example, M42X4.5 denotes a metric main one with an outer diameter of 42 mm and a pitch of 4.5 mm.

Fine threads, in addition, have a number in the designation indicating the thread number, for example 2M20X1.75 - the second metric fine, outer diameter 20 mm, pitch 1.75 mm.

Inch thread(Fig. 145, b) has an angle of 55° at the apex. Inch threads are cut in the manufacture of spare parts for machines with inch threads and should not be cut on new products. An inch thread is characterized by the number of threads per inch (1") length. The outer diameter of an inch thread is measured in inches.

Pipe thread(Fig. 145, c) is measured in the same way as the inch thread, in inches and is characterized by the number of threads per 1". The thread profile has an angle of 55°. For pipe threads, the diameter is conventionally taken to be the diameter of the hole of the pipe on the outer surface of which the thread is cut thread.

The tops of the protrusions of screws and nuts with pipe threads are made with flat or rounded cuts.

The flat-cut profile is easier to manufacture and is used for threads of conventional pipe connections. Pipe thread is designated: 1/4" PIPE; 1/2" PIPE. etc. (Table 25).

Table 25 Designation of threads in drawings

Thread type	Legend	Notation elements	An example of a bolt and nut thread designation
Metric basic	M	Thread outer diameter (mm) or outer diameter and pitch (mm)	M64 or M64X6 or 64x6
Metric small	1M		1M 64X4 or 64X4
	2M		2M 64X3 or 64X3
	3m		3M 64X2 or 64X2
	4M		4M 64X1.5 or 64X1.5
	5M		5M 64X1 or 64X1
Trapezoidal	LADDER	Outer diameter and thread pitch (mm)	LADDER. 22x5
	UP		UP 70X10
Inch with a profile angle of 55°		Nominal thread diameter in inches	1"
Pipe cylindrical	TUBE PR* PIPE. KR**	Symbol threads in inches	3/4" TUBE OL 3/4" TUBE KR
Pipe conical	TUBE CONIC.		3/4" TUBE

* Profile with flat-cut tops (straight). ** The profile is rounded.

Threads can be right-handed or left-handed; by the number of passes - one-, two-, three-pass and multi-pass.

In order to determine the number of thread starts, it is enough to look at the end of the screw or nut and count how many thread ends there are on it.

As a rule, all fasteners (bolts, screws, screws, etc.) have single-start threads.

In our metric world, it can sometimes be difficult to navigate other measurement systems. We are sometimes surprised how Americans or British can use outdated measures of length, mass, area, etc. And they, in turn, do not understand us - living according to the laws of a single System of Measurements. However, as with any rule, there are certain exceptions that are clear to everyone - residents of America, Foggy Albion, Europe, and Russia. This article is devoted to a review of pipe and metric threads, the variety of which one often encounters in everyday life.

Metric threads and their applications

Threaded connections are very common in construction, engineering, mechanical engineering, aerospace and everyday life. Even children in kindergarten know what a screw and a nut are, since classes with a construction set cannot do without these parts. Despite the fact that the first screw was invented by Archimedes, and our ancient ancestors widely used screw drives in presses for squeezing oil from olive pits and sunflower seeds, as well as for raising water for irrigating fields, the idea of ​​​​creating a real screw connection was realized only in the 15th century, when one of the Swiss watchmakers was first able to turn the first screw and nut using simple tools.

At the same time, humanity did not quickly come to the reasonable idea that carvings should be the same in all countries of the world. Thus, widespread and familiar to everyone who has had at least a little experience with technology, metric thread appeared and was described in standards only after the introduction of a unified System of Measurements based on the standards of the meter, kilogram and second. So the appearance and widespread use of metric carving dates back to the end of the 19th century. Until that time, inch threads dominated the world.

The main difference between a metric thread and an inch thread is that all its parameters are tied to a millimeter, and the profile of the thread itself is based on equilateral triangle, since everything is his angular dimensions are identical and equal to 60 degrees. In standardizing metric threaded connections, it is important that the nut and bolt have the same not only angular dimensions of the thread, but also its diameter and pitch. Many people, especially those who own cars, have encountered an incomprehensible phenomenon when a screw and a nut have the same diameter, but it is impossible to screw the screw into the nut. This suggests that in this place a thread with a smaller pitch is used and in order for the screw to be screwed in without problems, its thread pitch must also be reduced.

The standards describing metric threads indicate that they must be designated by the letter M, and then the diameter of the thread and its pitch are indicated. The range of metric thread diameters ranges from one to six hundred millimeters. The thread pitch ranges from 0.075 to 3.5 mm. Fine pitch threads are used for measuring tool, threads with a medium pitch are for parts and assemblies loaded and operating under vibration conditions, and threads with a large pitch are used for fastening heavy load-bearing structures.

When creating standards for metric threads, various tolerances were taken into account, which determine the degree of roundness of the outer edge of the thread and deviation from the profile so that the screw and nut can be freely tightened until it stops by hand.

Although metric threads have not found widespread use in sealed joints, such a possibility is included in the standards. Thus, threads with the designation MK are used for self-sealing connections due to the taper of the outer and internal thread. Moreover, for a hermetic connection it is not necessary that the screw and nut have a conical thread. It is enough that this thread is cut on the screw.

Cylindrical metric threads are quite rare. Her designation is MJ. The main difference is in the screw, which has an increased root radius on the thread, which gives the threaded connection based on cylindrical metric threads higher heat-resistant and fatigue properties. This type of thread is used in the aerospace industry. However, a regular metric screw can be screwed into a nut with such a thread.

Despite the universal predominance of right-hand threads in all devices and mechanisms, it is still necessary to use left-hand threads to implement certain functions. Metric left-hand threads are no different from right-hand threads, except for the direction of rotation, which is opposite to right-hand screws. If a regular screw is twisted clockwise, then the left one is unscrewed in the same direction.

You can also sometimes encounter multi-start metric threads. It differs in that not one spiral, but two or even three are cut simultaneously onto the bolt and nut. Multi-start threads are often used in high-precision equipment, for example, in photographic equipment, in order to unambiguously position the position of parts during mutual rotation. Such a thread can be distinguished from a conventional thread by two or three starts of turns at the end.

Despite the very wide application metric threads, in many developed countries of the world traditionally the so-called inch threads remain in greater use. And pipe threads are universally measured in inches. And, despite the strong differences between these types of threads, plumbers all over the world do not need to explain the differences between a half-inch pipe and a three-quarter pipe.

Inch threads and their application

The difference between inch threads and metric threads is that the angle at the top of the thread is 55 degrees, the thread pitch is calculated as the ratio of the number of thread turns per inch of thread length. An inch is understood as a distance equal to 2.54 cm. Which originally corresponded to the length of the first phalanx thumb human hands, which is the same for almost all people.

Since the apex angle is different than in metric threads, it is not possible to combine metric and inch threads. In countries with metric system Only inch pipe threads are used, which are designated by the letter G. The letter is followed by a fractional or whole denomination, which does not indicate the size of the thread, but the conditional clearance of the pipe in inches or fractions of an inch. A special feature of pipe threads is precisely the fact that it takes into account the thickness of the pipe walls, which can be thicker or thinner depending on the material of manufacture and the operating pressure for which the pipes are designed. Therefore, the inch standard for pipe threads is understood and accepted throughout the world as an exception to the metric rules.

In addition to simple cylindrical pipe threads, there are also conical pipe threads. It has the same characteristics as a regular pipe, with the exception of the taper, which allows you to create more airtight connections. Denoted by the letter R for external thread and Rc for internal. Left-hand threads are additionally marked with the letters LH, followed by a numerical value in whole and fractional shares inches.

For use in connections other than plumbing, inch threads with an apex angle of 60 degrees are used in the USA and Canada. There is a fairly wide range of these threads, which differ in the range of thread pitch and other characteristics. It is worth noting that some threads from the inch series coincide with metric ones, which in some cases can be beneficial. For example, in photographic equipment, the diameter of the connecting thread by which the camera is attached to a tripod is the same all over the world, regardless of the country of origin, since the characteristics of this thread are the same for both metric and inch threads.

However, one should not confuse the English inch industrial thread, which was approved back in 1841, and was developed by Joseph Whitworth himself. This thread practically replicates the pipe thread, since it has an angle at the apex of 55 degrees. Screws and nuts with such threads are not compatible with inch fasteners from America and Canada.

In this article, I want not only to provide dry facts about the sizes of inch pipe threads with references to standards and GOSTs, but to bring to the reader an interesting fact about the features of the designation of the latter.

So, those who have already encountered pipe threads have been more than once surprised at the discrepancy between the outer diameter of the thread and its designation. For example, a 1/2-inch thread has an outer diameter of 20.95 mm, although logically with metric threads it should be 12.7 mm. The thing is that inch threads actually indicate the through hole of the pipe, and not the outer diameter of the thread. At the same time, by adding to the size of the hole in the pipe wall, we get the overestimated outer diameter that we are accustomed to in the designation of metric threads. Conventionally, the so-called pipe inch is 33.249 mm, that is, 25.4 + 3.92 + 3.92 (where 25.4 is the passage, 3.92 is the pipe wall). The pipe walls are taken based on the working pressure for the thread. Depending on the diameter, the pipes also increase accordingly, since a pipe with a larger diameter must have thicker walls than a pipe with a smaller diameter for the same operating pressure.

Pipe threads are divided into the following:

Cylindrical pipe thread

This is an inch thread based on BSW (British Standard Whitworth) thread and corresponds to BSP (British standard pipe thread) thread, has four pitch values ​​28,19,14,11 threads per inch. Cuts on pipes up to size 6", pipes over 6" are welded.

The profile angle at the apex is 55°, the theoretical profile height is Н=0.960491Р.

Standards:
GOST 6357-81 - Basic standards of interchangeability.
Cylindrical pipe thread. ISO R228, EN 10226, DIN 259, BS 2779, JIS B 0202.

Symbol: letter G, numeric value nominal diameter of the pipe in inches (inch), accuracy class of the average diameter (A, B), and the letters LH for left-hand threads. For example, a thread with a nominal diameter of 1 1/4", accuracy class A is designated as G1 1/4-A. Once again, we would like to remind you that it should be borne in mind that the nominal thread size corresponds to the pipe clearance in inches. The outer diameter of the pipe is in some proportion with this size and more accordingly to the thickness of the pipe walls.

Designation of cylindrical pipe thread size (G), steps and nominal values ​​of outer, middle and inner thread diameters, mm

Thread size designation		Step P	Thread diameters
Row 1	Row 2		d=D	d 2 =D 2	d 1 =D 1
1/16"		0,907	7,723	7,142	6,561
1/8"			9,728	9,147	8,566
1/4"		1,337	13,157	12,301	11,445
3/8"			16,662	15,806	14,950
1/2"		1,814	20,955	19,793	18,631
	5/8"		22,911	21,749	20,587
3/4"			26,441	25,279	24,117
	7/8"		30,201	29.0З9	27,877
1"		2,309	33,249	31,770	30,291
	1⅛"		37,897	36,418	34,939
1¼"			41,910	40,431	38,952
	1⅜"		44,323	42,844	41,365
1½"			47,803	46,324	44,845
	1¾"		53,746	52,267	50,788
2"			59,614	58,135	56,656
	2¼"		65,710	64,231	62,762
2½"			75,184	73,705	72,226
	2¾"		81,534	80,055	78,576
3"			87,884	86,405	84,926
	3¼"		93,980	92,501	91,022
3½"			100,330	98,851	97,372
	3¾"		106,680	105,201	103,722
4"			113,030	111,551	110,072
	4½"		125,730	124,251	122,772
5"			138,430	136,951	135,472
	5½"		151,130	148,651	148,172
6"			163,830	162,351	160,872

This article will discuss concepts related to threaded connections such as metric and inch threads. To understand the intricacies associated with a threaded connection, it is necessary to consider the following concepts:

Tapered and cylindrical threads

The rod itself with tapered thread is a cone. Moreover, according to international rules, the taper should be 1 to 16, that is, for every 16 units of measurement (millimeters or inches) with increasing distance from the starting point, the diameter increases by 1 corresponding unit of measurement. It turns out that the axis around which the thread is applied and the conditional straight line drawn from the beginning of the thread to its end along the shortest route- not parallel, but located at a certain angle to each other. To explain it even more simply, if we had a threaded connection length of 16 centimeters, and the diameter of the rod at its starting point was 4 centimeters, then at the point where the thread ends, its diameter would already be 5 centimeters.

Rod with cylindrical thread is a cylinder, therefore there is no taper.

Thread pitch (metric and inch)

The thread pitch can be large (or main) and small. Under thread pitch refers to the distance between the threads from the top of the thread to the top of the next thread. You can even measure it using a caliper (although there are also special meters). This is done as follows - the distance between several tops of the turns is measured, and then the resulting number is divided by their number. You can check the measurement accuracy using the table for the corresponding step.

Cylindrical pipe thread according to GOST 6357-52
Designation	Number of threads N by 1"	Thread pitch S, mm	O.D thread, mm	Average diameter thread, mm	Inner diameter thread, mm
G1/8"	28	0,907	9,729	9,148	8,567
G1/4"	19	1,337	13,158	12,302	11,446
G3/8"	19	1,337	16,663	15,807	14,951
G1/2"	14	1,814	20,956	19,754	18,632
G3/4"	14	1,814	26,442	25,281	24,119
G7/8"	14	1,814	30,202	29,040	27,878
G1"	11	2,309	33,250	31,771	30,292

Nominal thread diameter

The labeling usually contains nominal diameter, which in most cases is taken to be the outer diameter of the thread. If the thread is metric, then you can use a regular caliper with scales in millimeters to measure. Also, the diameter, as well as the thread pitch, can be viewed using special tables.

Metric and inch threads with examples

Metric thread– has the designation of the main parameters in millimeters. For example, consider an elbow fitting with an external cylindrical thread. EPL 6-GM5. In this case, EPL says that the fitting is angled, 6 is 6 mm - the outer diameter of the tube connected to the fitting. The letter “G” in its marking indicates that the thread is cylindrical. “M” indicates that the thread is metric, and the number “5” indicates the nominal diameter of the thread, equal to 5 millimeters. Fittings (of those that we have on sale) with the letter “G” are also equipped with a rubber O-ring, and therefore do not require fum tape. The thread pitch in this case is 0.8 millimeters.

Basic parameters inch thread, according to the name, are indicated in inches. This can be a 1/8, 1/4, 3/8 and 1/2 inch thread, etc. For example, let's take a fitting EPKB 8-02. EPKB is a type of fitting (in this case a splitter). The thread is conical, although there is no reference to this using the letter “R”, which would be more correct. 8 - indicates that the outer diameter of the connected tube is 8 millimeters. A 02 - that the connecting thread on the fitting is 1/4 inch. According to the table, the thread pitch is 1.337 mm. The nominal thread diameter is 13.157 mm.

The profiles of the conical and cylindrical threads coincide, which allows fittings with conical and cylindrical threads to be screwed together.

Her Majesty the trumpet! Of course, it makes our lives better. Something like this:

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.

In addition, the actual size of the internal diameter often does not coincide with Dy.

Let's take a closer look at how we can continue to live with this. Pipe thread a separate article is devoted. 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 stainless steel a problem arises - the size of the designated inch does not match ( 33.5 mm) to his 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 standard pipe amounts to 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, both the outer and inner diameters should be taken into account.

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 passage

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 outer, 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 a measuring tape (this is how women measure their waist). 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 special equipment are bent to the 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 regulated 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).

The regulatory documentation indicates the diameters of products produced by electric welding. 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

The production of a 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.

Important to know!

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

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

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