To cut the external view of the thread on metal pipes, specialists use special tools called a lerka or a die. The purpose of the devices in question is inch. The shape of the die should be an inch conical according to GOST tubular, round, square, hexagonal.
Lerok classification (depending on the body design): p>split;
sliding;
solid body.
This type of thread-cutting dies is called "American", since their main purpose is to make inch threads. Used for the cutting procedure, special devices called a crank. The wrenches often come with lehrs.
Dies for cutting tapered inch threads are more used in the USA and Europe. In our country, it is gaining popularity, it is more often used for the installation and repair of pipelines or equipment.
What to consider when choosing an inch conical die
First of all, pay attention to the thread pitch - we are talking about distance between coils. According to GOSTs, there are special sizes for tools - from ⅛ inch to 2 inches. This tool is used in the processing, manufacture and straightening of conical inch threads on rods or pipes. Cutting is done smoothly, it is desirable to do it in one pass.
To perform finishing, you need to use a calibrating lerka - it creates the final shape of the thread profile. An important point: the tool is subjected to a very high load at the end of passing through the die. When it comes time to choose a lerki to cut inch taper threads, remember that they always have the appropriate markings on the body. They usually indicate the letter "K". The main characteristics of such dies include the angle of the intake body from 30 to 55 degrees, as well as the small width of the pen. This is necessary to reduce friction. One side of the die is elongated, cone-shaped. -npt-national-pipe-taper-thread/" rel="external noopener">NPT taper dies are secured with set screws, or it is secured in taper chucks. It has recesses with a conical shape and angular grooves on the outside of the cylinder, with the help of a grinding wheel, it is possible, by cutting the die along the jumper, to perform diametrical adjustment. When working with a round die, you have to use knobs with 5 screws - they help in adjusting the diameter of the threads being cut.
A solid die has a high rigidity property, therefore, metric or conical threads are cut with high quality. However, this die has a low level of wear resistance.
