In mechanical engineering, the most common connection is a threaded one. If it is of high quality, the whole structure is reliable and durable.
Threading is the process of removing chips from a shank or hole with a special tool or plastic deformation (knurling) method.
There are single-start and multi-start threads, right-handed or left-handed. Another parameter is the pitch, the distance between two ridges. There are several thread profiles: universal - ordinary triangular; trapezoidal - its profile is made in the form of a trapezoid; persistent - for devices operating under high pressure, and pipe, which is used to connect pipes. There is a standard range of threaded connection diameters.
Threading can be done manually, when the cutting tool is inserted into a hand crank or drill, or mechanically, when cutting is done on a machine - drilling or turning.
Before this, it is necessary to perform an additional operation on the part - to make the desired diameter of the hole or rod. If you need to make internal cutting, selecta drill so that the tap smoothly enters the hole, but at the same time captures the volume of metal necessary to remove the chips. Otherwise, the tool may break and the thread will turn out to be loose. Usually, the diameter of the desired workpiece is selected according to existing tables.
Threading inside a hole is done with a special cutting tool called a tap. It has a working part, which performs the cutting process itself, and a shank designed to fix the tool in the chuck of a drilling machine, lathe, hand drill or wrench. The working part of the tool is made of high speed steel or sometimes hard alloy.
Threading with a tap is a rather time-consuming and complex job that requires utmost care. First you need to expose the product so that the tap is strictly in the center, otherwise marriage cannot be avoided. When working with a tap, there are difficulties in removing chips, because. access to the hole in which threading is performed is difficult. The taps themselves can often break due to their low rigidity.
However, tapping has some advantages:
- simplicity of design and manufacturability;
- cutting occurs due to self-feeding;
- thread accuracy depends on the correct tap.
Cutting an external thread is done with a special cutting tool called a die.
Die for threadingmade in the form of a nut made of high-speed or tool steel. The sharp edges of the working profile of the tool allow you to easily remove the chips from the core, and the chips themselves freely go into the hole. Before threading, the part is machined to the required diameter, a chamfer is removed at the end of the bar to facilitate the entry of the part into the die and its more correct centering in the part. The plate is fixed in the plate holder. When cutting threads, it is desirable to apply lubricant to the part. This makes the process easier.
