Pipe thread and its characteristics

The processing of a steel rod or pipe by the method of applying a screw thread by a special tool is called a threaded connection. It is applied to nuts, screws, bolts, which later serve to connect different units and assemblies, as well as pipe threads are used for the installation of pipelines.

The main elements of this type of connector 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, the part will be used, the thread on the pipe can be either left or right. Also it can be divided into a special and fastening.

The main type of fasteners is a triangular profile, and special joints are rectangular and a number of other profile types.

The thread applied to the screws, bolts, nuts is triangular, because it serves for fastening. The distance between the scallops or the bases of the depressions of the two turns nearby is called the step. The depth of such a connection is the distance from the bottom to the top of the turn.

Fixing pipe thread or triangular, sometimes 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 thread pitch, except for millimeters, is also in its fractions.

But the tubular inch thread has an angle of 55 degrees, although the profile is the same as the metric. The difference is that the measurements take place in inches rather than millimeters at the expense of a larger step.

When installing plumbing pipes and parts with inch cutting are used. It can be fastened and tubular. On the pipes, in view of the fact that its depth is regulated by the thickness of the pipe walls, the thread is shallower. But due to more turns - this connection is denser. But for stronger connections, there is a fixing thread, which, as mentioned above, is cut on bolts, screws, nuts made of solid metal.

Fixing pipe thread, except for automatic cutting, can be cut manually with the use of dies. Dies are also divided into types, depending on their device. They are prismatic, round, sliding and solid.

For example, sliding dies, cutting the full thread, you can tolerate small deviations in the diameter of the metal rod. And using solid round plates, deviations in diameter are already unacceptable.

The thread on the pipe is cut in the following way: it is necessary to place and secure the workpiece vertically and using round dies, go through the intended length at a time. If the sliding dies are used, the cutting will take place in two or three passes.

When cutting the right threaded joint, the klypp 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 with the help of screwing the nut.

During the cutting process, the pipe thread in the steel elements and the die itself are heated. To cool them, use sulfophrezol or linseed oil. To cool the details of cast iron, turpentine is the most suitable.

The inner turns are cut with a tap. In the same way, the part is fixed in the vice, and the first tap in the finished hole is marked. After removing a certain layer of metal, using the second and third taps, already cut the full turns. It is necessary to constantly ensure that the tap and hole axes coincide. From time to time, unscrew the tap in the reverse direction by ¼ turn to remove chips.