Pipe thread. Types of pipe carving. Methods of knurling and measuring the thread pitch

One of the simplest, but sufficiently reliable methods of connecting water and gas pipes are threaded connections. Pipe thread, necessary in this case, is obtained by creating a spiral recess (channel). Cutting of turns is possible both on external, and on the inner surface of the product. Kneading must meet all the presented standards, otherwise the quality of the connection cannot be guaranteed.

There are different types of pipe threads, each of which has its own characteristics

What can be a pipe thread?

Regulatory documents allow the use of such varieties:

1. Cylindrical. To obtain it requires a spiral cut with a profile, formed by an isosceles triangle, with an angle at the apex equal to 55 degrees.
2. Conical. Spiral cutting is performed, identical to the previous one, but with a taper on the beveled section of the pipe, equal to 1 to 16.
3. Inch. The angle at the vertex of an isosceles triangle in this case will be equal to 55 degrees. In the United States, and in Canada, inch cylindrical threaded profiles are used, the angle at the apex of which is 60 degrees. Their international name is NPSM, they are produced in a range of sizes from 1/16 inches and up 24 inches.

The popularity of the latter option, inch pipe thread, has been coming to naught lately. Cylindrical or conical cutting is much more often used in new pipelines.

Cylindrical type has its own designation - the letter "G", the presence of a conical cut of the pipe indicates the marking with the letter "R" or "K" (for conical inch cuts). The parameters of the metric cylindrical knurling are highlighted in the Guest number 8724-81. For metric conical cutting there is GOST-25229-82, if the thread is conical inches, then GOST is used 6357-81.

The conical thread gives a stronger connection, therefore pipes with such cutting are used in the industry and conditions, which requires increased reliability

Conical thread is used for household purposes less often, basically this type of thread has become widespread in the assembly of hydraulic devices, construction of oil and fuel pipelines for cars and aircraft. The conical type of cutting has a stronger connection, close to the monolith. Conical knurls, designed to work under high pressure, are made according to the American NPT standard.

The main parameters of threaded connections, in addition to the above varieties, there are such factors:

1. Direction, Location.
2. The unit of measurement of the profile is inch or metric (in mm).
3. Step - repetitive distance between turns.
4. Internal diameter of slicing.

There is also such a concept, as non-standard threads. They happen, example, rectangular or square. Production of this type of cutting is possible only on condition of providing by the customer of detailed drawings with the indication of all individual parameters of a carving..

What is the difference between metric thread and pipe?

The main difference between the two types of cutting is the shape of the threaded ridge and depressions. The metric profile is based on an equilateral triangle, therefore, all the angular dimensions of this type of cutting are equal and make up 60 degrees, while the inch pipe has angular dimensions 55 degrees. All metric thread parameters are bound to the millimeter, while the dimensions of the pipe thread are calculated in inches. Another nuance - the size of the pipe thread takes into account the wall thickness of the product, which are different depending on the operating pressure, on which these or those pipes are calculated.

The parameters of the metric thread are presented in millimeters, and inches - in inches

Products with metric type of slicing must be marked with the letter "M". The dimensions of the metric profile are in the range from 1 mm to 600 mm. Threaded metric pitch can range from 0,075 mm to 3,5 mm. Products with the smallest metric thread pitch are used for fine work (measuring instrument), with a medium step - to create parts and assemblies, operating in conditions of constant vibration. The largest metric threads are involved in the construction of heavy load-bearing structures.

It is interesting! In tubes with an inch knurled pitch is calculated in the form of the ratio of the number of turns per inch of length of the knurled thread.

Inch thread, however, occurs in industry and everyday life more often, than metric. Pipe thread is measured almost everywhere in inches - a more universal unit of measurement for the water and gas industry.

Since different types of knurling have different angles at the vertices, combine two types of thread, even have identical dimensions, impossible. To make the transition from metric thread to pipe requires special shaped elements - adapters.

Features of a round carving

This type of slicing can be found on sanitary fittings (regulated by the state standard number 13536-68) and on lighting fixtures, as well as on the bases and cartridges for them. This variety makes it possible to obtain compounds, periodically subject to review. The profile for round threaded connections is obtained by connecting two arcs with the same radius. Thread pitch is always measured in millimeters, and the letters "Kr" are used as a designation.