Threading is a technologically important operation, which determines the strength of the threaded connection, the service life of the product and the stability of the assembly. Even a small deviation in the diameter or depth of the hole can lead to thread failure, part deformation, or failure of the entire structure.
The importance of precise drilling
Threaded drilling is an important step in metalworking, which determines the quality of the joint, the reliability of the structure and the service life of the product. If the hole is made inaccurately, this can lead to thread breakage, part deformation, rapid tap failure, or loosening of the joint. Despite the apparent simplicity, the process requires a careful approach and compliance with a number of technological rules.
Determination of thread parameters
First of all, it is necessary to determine the parameters of the future thread: its type (metric, inch, pipe), diameter, pitch, depth and cutting method. It is also important to consider the material of the part — the choice of drill, cutting modes and the need for coolant depend on this. For example, when threading soft metals such as aluminum, a different approach is often required than when working with stainless or tool steel.
Choosing the drill diameter
One of the key points is choosing the right drill diameter. A simple formula is usually used for this: the diameter of the hole is equal to the diameter of the thread minus its pitch. However, in practice, this value is often adjusted depending on the material and cutting conditions. In the case of processing hard alloys, it is recommended to slightly increase the diameter of the hole to reduce the load on the tool.
Preparation for drilling
Before drilling, it is necessary to core the center, especially when working manually. This prevents the drill bit from shifting and ensures accurate positioning. If you are using a drilling machine, it is advisable to start with a centering drill or a conductive sleeve. It is also important to calculate the hole depth correctly. For through threads, a small margin is made — for two or three turns. For blind holes, an additional recess of 1.5–2 mm is provided to ensure the exit of the chips and the free stroke of the tap.
Drilling and cooling modes
During drilling, it is necessary to use sharpened tools and, if possible, apply coolant. This is especially true when working with stainless steels and other difficult-to-process materials. The rotation speed of the drill and the feed are selected based on the material of the part and the diameter of the drill. When working manually, it is extremely important to eliminate the beating, which leads to the ovality of the hole and makes it difficult
