The processing of a steel bar or pipe by the method of applying a screw thread with a special tool is called a threaded connection. It is applied to nuts, screws, bolts, which subsequently serve to connect various components and assemblies, as well as pipe threads used for installation of pipelines.
The main elements of this type of detachable connection are its pitch, profile, groove depth and outer and inner diameter. Profiles are divided into several types: trapezoidal, triangular, rectangular and others. What is a profile? If you make a cross section, then the resulting shape is the profile.
Depending on the purpose for which the part will be used, the thread on the pipe can be either left or right. It can also be divided into special and fixing.
The main type of fixing connections is a triangular profile, and special connections - a rectangular and a number of other types of profile.
The thread applied to the screws, bolts, nuts is triangular, because it serves for fasteners. The distance between the scallops or the bases of the troughs of the two turns located nearby is called a step. The depth of such a connection is the distance from the bottom to the top of the turn.
Fixing pipe thread or triangular, happens inch and metric. As a rule, it is the main type of fasteners in the automotive industry, instrument making. Diameters, both internal and external, are measured in millimeters, and the threaded pitch, in addition to millimeters, is also in its parts.
But the inch pipe thread has an angle of 55 degrees, although the profile is the same as that of the metric. Their difference is that measurements take place in inches, not millimeters, due to a larger step.
At installation of bathroom equipment pipes and details with an inch cutting are used. It is fastening and pipe. On pipes, since its depth is regulated by the thickness of the pipe walls, the thread is finer. But due to a larger number of turns, such a connection is denser. But for stronger joints, a fastening thread is suitable, which, as mentioned above, is cut into bolts, screws, nuts made of solid metal.
The fastening pipe thread, in addition to automatic threading, can be cut manually using dies. Dies are also divided into types, depending on their device. They are prismatic, round, sliding and solid.
For example, by sliding dies, cutting a full thread, you can allow small deviations in the diameter of the metal bar. And using solid round dies, deviations in diameter are already unacceptable.
The thread on the pipe is cut as follows: it is necessary to vertically install and fix the workpiece, and, using round dies, go through the intended length at a time. If sliding dies will be used, then the cutting will take place in two or three passes.
When cutting the right threaded connection, the dies should be rotated to the right, and when cutting the left one - to the left, while remembering to do a couple of turns back to remove the chips. When everything is ready, you can check by tightening the nut.
In the process of cutting, the pipe thread in the steel elements and the die itself are heated. Sulfofresol or drying oil is used to cool them. Turpentine is most suitable for cooling parts made of cast iron.
The inner turns are cut with a tap. In the same way, the part is fixed in a vice, and the mark is made with the first tap in the already prepared hole. After removing a certain layer of metal, using the second and third taps, already complete turns are cut. It is necessary to constantly ensure that the axis of the tap and the holes coincide. From time to time we unscrew the tap in the opposite direction by ¼ turn to remove chips.