If we consider it from a closer angle, it can be seen that they consist of two shape elements. They have an elevated part, called the crest of the thread and a recess, called the thread. If these elements run helically about a cylindrical body, this is called an outside or outer thread. If it is inside a hole, it is called an inside or inner thread.
Bolts are ideally suited to forming stable, non-permanent component joints and connections. A nut with a suitable mating thread is needed to fix the bolt. Bolted elements, unlike welded components, can be separated later using simple tools.
But they must always fit together precisely. There is a very large diversity of bolt forms. In standard catalogues, among other things, a differentiation is made between ISO, round, trapezoidal and V shapes, which can then in turn be divided into normal and fine. Many countries have their own standards. There are also company-specific and industry-specific threads. For example, in the sanitary (plumbing) segment, the threads are different to those used in bicycle and vehicle production. These standard catalogues, which contain the necessary designations, help to keep an overview of the diverse forms available.
There are two production methods. A differentiation is made between chip removal and chipless methods:
Chip removal (material removal) production methods by cutting and milling
As the name system, in machining (chip / material removal) production methods material is cut out of the workpiece. This produces a long, twisted chip. An outside thread can be cut out manually using dies (threading dies) or they can be made using a special cutting machine.
Both manual drills and mechanical production methods exist for inside threads. If particularly precise results are required, it is advisable to use CNC milling machines. These machining centres have computer-controlled tools for producing top quality threads.
Compared to the chipless methods, machining methods have one disadvantage. The cutting out weakens the thread due to the material loss and it cannot be subjected to the same loads as a comparative thread made by chipless methods. How can this be explained?
Chipless production by pressing and punching
The chipless production of inside and outside threads is principally identical. In both methods special tools are pressed into the material. In the case of outside threads the material is pressed with a large force from the surface of a blank, from the parent material to the crests.
In the case of inside threads the process is identical, only the tool penetrates a prepared hole and forms the thread in the hole. As there is no material loss in this method, they can be subjected to much higher loads in use.
Production at Rime
We can make threads using both machining (chip removal) and chipless methods. A modern CNC machining centre is available for the chip removal method. For chipless production we use our CNC punching machine, which can make threads quickly and with very high precision.