Her Majesty Trumpet! It certainly makes our lives better. More or less like this:
The key characteristic of any cylindrical pipe is its diameter. It may be internal Do) and outer ( Dn). Pipe diameter is measured in millimeters, but the unit of pipe thread is inch.
At the junction of the metric and foreign systems of measurement, as a rule, the most questions arise.
In addition, the actual size of the inner diameter often does not match Dy.
Let's take a closer look at how we can live with this. A separate article is devoted to pipe threading. Read also about profile pipes, which are used for the construction of structures.
Inches versus 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 an inch ( 1/2", 3/4" ), are the generally accepted standard in water and water and gas supply.
What is the difficulty?
Dimension the pipe diameter 1" (how to measure pipes is written below) and you will get 33.5mm, which naturally does not coincide with the classic linear table for converting inches to mm ( 25.4mm).
As a rule, the installation of inch pipes goes without difficulty, but when they are replaced with pipes made of plastic, copper and stainless steel, a problem arises - a mismatch in the size of the designated inch ( 33.5mm) to its actual size ( 25.4mm).
Usually this fact is puzzling, but if you look deeper into the processes taking place in the pipe, then the logic of the size mismatch becomes obvious to the non-professional. It's pretty simple - read on.
The fact is that when creating a water flow, the key role is played not by the outer, but by the inner diameter, and for this reason it is he who is used for designation.
However, the discrepancy between designated and metric inches still remains, because the internal diameter of a standard pipe is 27.1 mm, and enhanced - 25.5mm. The last value is pretty close to equality 1""=25,4 but still they are not.
The answer is that to indicate the size of the pipes, a nominal diameter rounded to a standard value is used (nominal bore Dy). The value of the conditional passage is selected so that the throughput of the pipeline increases from 40 to 60% depending on the growth of the index.
Example:
The outer diameter of the pipe system is equal to 159 mm, pipe wall thickness 7 mm. The exact inside diameter will be D \u003d 159 - 7 * 2 \u003d 145 mm. With wall thickness 5 mm size will be 149 mm. However, both in the first and in the second case, the conditional passage will have one nominal size 150 mm.
In situations with plastic pipes, transition elements are used to solve the problem of inappropriate sizes. If it is necessary to replace or dock 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.
Nominal bore table in inches
| Doo | inches | Doo | inches | Doo | 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 and gas pipelines, electro-welded straight-seam, steel seamless hot-formed and polymer pipes
Correspondence table for the diameter of the nominal bore, thread and outer diameters of the pipeline in inches and mm.
|
Nominal pipe diameter Dy. mm |
Thread diameter G". inch |
Outer pipe diameter Dn. mm |
||
|
Stacked water/water/gas pipes GOST 3263-75 |
Pipes steel electrowelded longitudinal GOST 10704-91. Pipes steel seamless hot deformed 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- diameter designation standard, used in plumbing engineering systems
SMS- Swedish standard for pipe and valve diameters
DIN/EN- the main European assortment for steel pipes according to DIN2448 / DIN2458
DU (Dy)- conditional pass
Tables with the dimensions of polypropylene pipes are presented in the following article >>>
Correspondence table for the nominal diameter of pipes 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 | 1½ | 48,30 | 38,00 | 40,43 | 40 |
| 57 | 2 | 60,30 | 50,80 | 52,53 | 50 |
| 76 | 2½ | 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 pipe
| Pass, 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 be assembled with your own hands from an ordinary metal pipe? This is for everyone!
Which pipe is considered small - medium - large?
Even in serious sources, I had to observe phrases like: “We take any pipe of medium 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 and external. The first is important when calculating the transport capacity of water or gas, and the second for determining the ability to withstand mechanical loads.
External diameters:
From 426 mm is considered large;
102-246 is called the average;
5-102 is classified as small.
As for the inner diameter, it is better to look at a special table (see above).
How to find out the pipe diameter? Measure!
For some reason, this strange question often comes to e-mail and I decided to supplement the material with a paragraph about metering.
In most cases, when buying, it is enough to look at the marking 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:
After receiving 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).
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 wrapped around the measuring teeth. We look at the desired value on a double scale.
Arm yourself with a tape measure or measuring tape (women measure their waist like this). 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 Pi number.
Example:
Imagine that in girth (circumference L) your pipe 59.2 mm. L=ΠD, resp. diameter will be: 59.2 / 3.1415= 18.85 mm.
Types of steel pipes according to their production method
Electrowelded (straight-seam)
For their manufacture, strips or sheet steel are used, which are bent to the desired diameter on special equipment, and then the ends are connected by welding.
The impact of electric welding guarantees a minimum joint width, which makes it possible to use them for the construction of gas pipelines or water pipelines. The metal in most cases is carbon or low-alloy.
The indicators of finished products are regulated by the following documents: GOST 10704-91, GOST 10705-80 GOST 10706-76.
At the same time, please note that a pipe made in accordance with standard 10706-26 is distinguished by maximum strength among its own kind - after creating the first connecting seam, it is reinforced with four additional ones (2 inside and 2 outside).
The regulatory documentation indicates the diameters of products manufactured by electric welding. Their size is from 10 to 1420 mm.
Spiral-seam
The material for production is steel in rolls. Products are also characterized by the presence of a seam, but unlike the previous production method, it is wider, which means that 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 under the number 8696-74 .
Seamless
The production of a particular type involves the deformation of specially prepared steel blanks. The deformation process can be performed both under the influence of high temperatures and in a cold way (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 the diameters, the standards control their manufacture with a value of up to 250 mm. When buying products with sizes exceeding those indicated, you have to rely only on the integrity of the manufacturer.
It's important to know!
If you want to buy the most durable material, buy cold-formed seamless pipes. The absence of temperature effects has a positive effect on the preservation of the original characteristics of the metal.
Also, if an important indicator is the ability to withstand internal pressure, then choose round products. Profile pipes cope better with mechanical loads (metal frames are well made from them, etc.).
Here are a couple more great slides of creative advertising for a pipe manufacturer:
Very often on the packaging (box) with a mixer, in the list of product characteristics, you can see the figure 3/8 inch in the column "connecting size".
What is this size, 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 hose. On one side of such a hose, clad in a metal braid, a 10 or 11 millimeter wrench fitting and a threaded end of 10 millimeters, or 9.5 millimeters, which corresponds to three-eighths of an inch.
They look like this.
First, a short fitting is screwed to the mixer, followed by a long one. This is so that the edges of the fittings and the thickening of the crimping do not interfere with each other.
There is an alternative for reinforced flexible hoses - bellows hoses for faucets. They are not much more expensive, but their service life is a multiple of the service life of a rubber braided hose. So if the usual flexible eyeliner lasts 3-4 years, then the bellows pipe lasts up to 10 years.
At the second end, a flexible hose can have a thread instead of a nut, complete with mixers, more often there is still a nut, so consider if there is a nut at the outlet of your pipeline, you will need to purchase a nipple -
The diameter of the pipes in inches and millimeters are very important indicators. Many have faced the challenge of replacing or installing piping and finding the right materials for the job.
It is difficult to understand the huge number of proposals on the construction market, therefore, before buying, 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 for converting inches to millimeters and vice versa
An example of how to enter data into a calculator
In writing the size in inches, you should separate the integer part of the number from the fractional (if any) with a space: for example, 10 1/4, or 20 4/8; otherwise you get 101/4 and 204/8. Fractional numbers in millimeters are entered through a dot, not a comma (25.4 and not 25.4).
Enter the data for the calculation in the following. in order: click the left mouse button in the window of the corresponding parameter to make the blinking cursor appear; enter your numbers. The fractional part of an inch is entered without a sign.
1 inch = 25.4 millimeters (mm). Currently, an inch, due to its clarity, is often used to measure the diameters of water and gas pipes and threads. Many parts are also sized in multiples of inches. In addition to whole inches, measurements are taken in fourths (1/4″), eighths (1/8″), sixteenths (1/16″), thirty-seconds (1/32″) of an inch, etc.
If you have any questions about using the online calculator, you can always ask a question in the comment form. We also strongly recommend that you read the instructions (located under the calculator).
How to convert inch values to metric notation
The conversion of inches to metric pipe volumes is performed using special tables. Here is an example of such a table:
In order to convert the metric diameter of the pipe assortment, it is necessary to perform rounding in the direction of increase. When making this translation, you need to remember that according to international standards, one inch is taken into account as 2.54 cm.
With such data, the translation can be performed using the simplest calculator. Now that the cross section of the pipe assortment has been calculated, its volume should be correctly calculated.
In practice, in order to translate the measurements of steel options, it must be taken into account that the inch indicators in the calculation will not be equal to the indicator in mm. The reason is that when marking, the internal volume is prescribed.
After the unit of measurement, the conditional passage, indicated by an integer, becomes. It is for these reasons that in order to translate values, they need to be rounded. 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 perform a translation based on a special table. Professionals will help translate the required values, and help you choose the right products and other parts for the pipeline.
Translation tables
In the construction of 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 tubular products are given by the following indicators:
- Dn - external Ø.
- Dv - internal Ø.
- h is the wall thickness.
Previously, only steel lines were used, 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 a half-inch pipe billet, but also its throughput.
And the outer girth of a half-inch blank is 2.1 cm. Therefore, in the table near the half-inch thread, the word pipes must be added. Knowing the exact dimensions of the half-inch and any other type of assortment, you can quickly make the right choice of the right volumes.
This is clearly seen in the table:
| Dimensions (in inches) | 1/2 | 3/4 | 7/8 | 1 | 1,5 | 2 |
| Internal Ø (in 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 |
Now it is customary to indicate these dimensions as shown in the following table provided:
The first table of diameters ( its symbolic designation is Ø, further it will be denoted in the article) of pipes shows values in millimeters, while inches are used in the second table ( international designation - inch or in, will be further indicated in the article). An inexperienced master may ask why? And what designations are considered correct?
The reason is that the metric system is used all over the world. This system is based on two indicators: conditional and nominal volume. These concepts are approached in different ways, but in the end they show the external volume. In essence, these quantities are dimensionless, but sometimes they are indicated in millimeters.
Analyzing tabular data, it is possible to compare products of domestic manufacturers and analogues of foreign production.
Interesting! Measurement discrepancies appeared simultaneously with the introduction of copper systems in Europe in the second half of the 20th century. In Russia at that time the standards for the metal assortment were determined in mm, and not in inch, this measurement system is widely used today.
Correspondence of two notation systems
Steel pipes are widely used in water and gas systems. Their dimensions are shown in whole values or their fractions. For example, a 1" tubular in mm would be 33.5, and a 2" tubular would be 67 in mm.
This of course does not correspond to the declared 25.4 and 50 mm. When laying fittings with inch designations for 1 and 2 inch products, there are no difficulties, but replacing with plastic and copper products requires taking into account the discrepancy in the designations.
Why is everything so complicated? The fact is that for the formation of a fluid flow, it is important to take into account the internal size. For these reasons, they began to indicate exactly this indicator for 1-inch, 2-inch and all other pipe materials. The most accurate indicators are considered in terms of conditional passage.
The nominal bore of 1-inch, 2-inch and the rest of the pipe range is equal to the dimensions of the clearance. To indicate the metric size of 1 inch, 2 inch and any other pipeline, it is recommended to use tables.
Precise 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 lay a heating system, it is necessary to determine and calculate the size of the assortment in the section 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 \u003d sqrt ((314 ∙ Q) / (V ∙ DT)).
- D is the internal volume of the pipe;
- Q is the heat flux, which is determined in kW;
- V denotes the speed of the heat carrier, it is determined in m / s;
- DT is the difference in temperature indicators at the inlet and outlet of the network;
- sqrt is the square root.
Watch the video
Despite the presence of formulas, tables help to quickly determine Ø. In this way, a lot of time is saved.
What is inch volume
Deciphering the diameter of the pipes 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. So, for example, the internal dimension of an inch pipe billet can be different: from 2.55 to 2.71 cm. This value varies depending on the wall thickness.
A 1 inch pipe has an outer diameter of 25.4 mm, a 2 inch pipe is 50 millimeters in metric measurement. Where do the numbers 33.249 and 66.498 come from in the technical parameters of a cylindrical pipe thread?
This thread on 1 and 2 inch products is performed on the outer volume. Therefore, the ratio of the thread diameter to the internal volume is conditional. Based on this, the dimensions of 1 and 2 inch tubing are calculated by adding the value of 25, 4 or 50 with two wall thicknesses of the tubular product.
Before deciphering, you need to take into account that measurements of the product must be performed not from the outside, but from the inside. Why is this needed? The fact is that by fastening sections of the highway from different materials, and taking measurements only from the outside, you can get the wrong result, which will lead to an error, since the entire assortment differs in wall dimensions.
Also, when deciphering, we must not forget that the standards of different manufacturers 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 in choosing the right products.
Correspondence of 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 choose the right pipe assortment.
Watch the video
When selecting a certain size, they are guided by tabular information, and when replacing a guide, we serve as the most approximate parameter. There is no exact correspondence in two different systems of measurement, therefore 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 measurements of dimensions, and take parts for work that exactly match each other.
Inch size expression
These indicators are written as an integer, a double stroke is placed next to it, for example, 3 ". Also, the dimensions of the pipe diameter, transmitted in inches, are prescribed in fractions, for example, ½.
If we consider these dimensions on specific examples of Du correspondences, then they will look like this:
- The diameter of a standard 12 inch pipe is 300.
- 3 inch tubular diameter is 80.
- 8 inch diameter of standard pipe is equal to 200.
- The diameter of a standard pipe, at 32, when translated into inches, is shown as 1 ¼
- Pipe diameter 40 mm in inch prescribe 1 ½
- Ø standard pipe at 15 inches is expressed as a number ½
- The Ø of a standard product per 4 inches in terms of metric is 100.
- Ø 3/4 inch pipe in metric conversion is 20.
- The Ø of a standard 1/2 inch pipe in metric translation shows the number 15.
Watch the video
Pipe diameter in inches and millimeters is used all the time. Knowing these dimensions, you can avoid great difficulties when connecting pipeline elements. And special tables help to find the necessary dimensions of the docking parts and correctly fit them.
An inch thread is used primarily to create pipe connections: it is applied both to the pipes themselves and to the 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 relevant GOST, giving tables of sizes for inch threads, which specialists are guided by.
main parameters
The normative document, which specifies the requirements for the dimensions of a cylindrical inch thread, 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 upper 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.
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 such diameters.
The 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 be inoperative, it will not be possible to pick up the second element of the created connection to 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
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 thread
According to their external features and characteristics, metric and inch threads do not have many differences, the most significant of which include:
- threaded comb profile shape;
- the procedure for calculating the diameter and pitch.
When comparing the shapes of threaded ridges, you can see that in inch threads such elements are sharper than in metric ones. If we talk about the exact dimensions, then the angle at the top of the crest 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 first are measured in millimeters, and the second, respectively, in inches. However, it should be borne in mind that in relation to an inch thread, not the generally accepted one (2.54 cm), but a special pipe inch, equal to 3.324 cm, is used. Thus, if, for example, its diameter is ¾ inch, then in terms of millimeters, it will correspond to a value of 25.
To find out the main parameters of an inch thread of any size, which is fixed by GOST, just look at a special table. In the tables containing the sizes of inch threads, both integer and fractional values \u200b\u200bare given. 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 the length of the product.
To check whether the pitch of the thread that has already been made corresponds to the dimensions specified by GOST, this parameter must be measured. For such measurements, carried out for both metric and inch threads according to one algorithm, standard tools are used - a comb, gauge, mechanical gauge, etc.
The easiest way to measure the pitch of an inch pipe thread is by using the following method:
- As the simplest template, a coupling or fitting is used, the parameters of the internal thread of which exactly correspond to the requirements given by GOST.
- The bolt, the parameters of the external thread of which must be measured, is screwed into a coupling or fitting.
- In the event that the bolt has formed a tight threaded connection with a coupling or fitting, then the diameter and pitch of the thread that is applied to its surface exactly correspond to the parameters of the template used.
If the bolt is not screwed into the template or is screwed, but creates a loose connection with it, then such measurements should be taken using a different coupling or other fitting. An internal pipe thread is also measured using a similar technique, only a product with an external thread is used as a template in such cases.
You can determine the required dimensions using a thread gauge, which is a plate with notches, the shape and other characteristics of which exactly match 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 under test corresponds to the required parameters will be indicated by the tight fit of the serrated part of the plate to its profile.
In order to measure the size of the outside diameter of an inch or metric thread, you can use a regular caliper or micrometer.
Slicing technologies
Cylindrical pipe thread, which belongs to the inch type (both internal and external), can be cut manually or mechanically.
Thread cutting by handThreading with a hand tool, which is a tap (for internal) or a die (for external), is performed in several steps.
- The pipe being processed is clamped in a vice, and the tool used is fixed in a wrench (tap) or in a die holder (die).
- The die is put on the end of the pipe, and the tap is inserted into the inside of the latter.
- The tool used is screwed into the pipe or screwed onto its end by rotating the knob or die holder.
- To make the result cleaner and more accurate, you can repeat the cutting procedure several times.
Thread cutting on a lathe
Mechanically, pipe threads are cut according to the following algorithm:
- The pipe being processed is clamped in the machine chuck, on the support of which the thread-cutting tool is fixed.
- At the end of the pipe, using a cutter, they chamfer, after which they adjust the speed of movement of the caliper.
- After bringing the cutter to the surface of the pipe on the machine, the threaded feed is turned on.
It should be borne in mind that the inch thread is cut mechanically using a lathe only on tubular products whose thickness and rigidity allow this. Performing pipe inch threads mechanically allows you to get a high-quality result, but the use of this technology requires the turner to have appropriate qualifications and certain skills.
Accuracy classes and marking rules
A thread related 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 the 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 the 1st class corresponds to the coarsest threads, and the 3rd - the most accurate, the dimensions of which are subject to very stringent requirements.
