Currently, the construction marketmaterials are often offered pipes, the sizes of which are indicated in inches. Many buyers may not pay attention to this, and therefore there is a possibility of purchasing a pipe with a size not corresponding to the required one. The reason for this lies in the fact that the inch thread (designation on the surface of the pipe), as the name implies, is measured in inches. In this case, one inch is equal to 25.4 millimeters. This value is different from the accepted millimeter standards, which can significantly complicate the choice of the required part.
The inch cylindrical thread provides for the display of pipe dimensions in inches, while the thread pitch is indicated in fractions of this unit of measure (because of its small size).
In connection with the discrepancy between the millimeter andIn practice, there is a significant difference between the thread sizes on the pipe. This is because the western standards read: inch thread denotes the inner diameter of the pipe. In this case, it is necessary to take into account the differences between the metric inch and, so-called, tubular.
For example, the pipe indicates that the inch threadhas a size of ½. Thus, you get a pipe with an outer diameter of 20.95 mm instead of the expected 12.7 mm. Consequently, the pipe inch is 33,249 mm and consists of the size of the direct passage and the double wall thickness.
From this example it can be seen that the use of this indicator is more acceptable, since such a system best characterizes the size that an inch thread has.
Now that the notation has become clear, you can proceed to the classification and assignment of this parameter.
Cylindrical inch thread according to the purpose and nature of the work is divided into:
- Mounting thread.This type is traditionally referred to as metric thread and inch, having a triangular profile. Metric is used in the design of new machines and aggregates, while the latter is necessary for the production of various spare parts.
- Special thread includes many different sizes that do not meet the standards.
Metric thread is often produced with a profile having an angle of 60 °. All values, whether thread pitch or outer diameter, are denoted in millimeters.
By the magnitude of the step, one main and 5types of auxiliary thread (it is also called shallow). It should be noted that such a thread is considered to be stronger than a large one (at absolutely equal external diameters). The undoubted advantage of fine carving is also the small angle of the helix and, as a result, increased resistance to twisting.
Thread of this type is used in the mostloaded hollow parts, as well as in elements that are subject to strong shocks and shocks. Adjusting nuts also have a similar thread, because it allows for more precise adjustment.
In addition, an inch thread can beangle of rotation 55 °. In this case, the diameter is still specified in inches, but the thread pitch is determined by the number of threads per inch. A similar type is used in various threaded joints to mechanically fix the parts together.
