Internal thread processing is an important part of mechanical manufacturing and involves a variety of methods and tools. Here is a detailed introduction to internal thread processing:
1. Processing method
Rolling Method: This is one of the most commonly used methods in internal thread processing. Threads are formed on the surface of the workpiece by mounting a thread cutter on a rolling head and rotating it while advancing the workpiece. This method is characterized by high efficiency and high accuracy.
Shredding Method: This is another major method. Cutting methods generally include turning and milling. Turning is carried out on a lathe using a form turning tool or thread comb cutter; milling is carried out on a thread milling machine using a disc cutter or comb. The cutting method is suitable for various materials and achieves high processing precision.
Spiral EDM: This is a machining method using electric sparks. An electrode and a spiral guide are placed inside the workpiece, and through the rotation and movement of the electrode, an arc is generated in the working fluid for processing. This method is suitable for difficult-to-machine materials and internal threads with complex shapes.
Plasma spray welding: This is a high-energy processing method that uses a plasma beam to directly form wires on the surface of the workpiece. This method has the advantages of fast processing speed and small heat affected area.
2. Processing elements and geometry The geometry of internal threads is mainly based on the pitch diameter and pitch of the thread. Thread pitch is the axial distance along the thread between one point on the thread and the next corresponding point on the part. The effective diameter of a thread is approximately halfway between large and small diameter. Additionally, internal threads also include elements such as tooth bottom, tooth flank, and tooth top.
3. Processing tools and equipment When processing internal threads, various cutting tools and equipment are required. For example, the cutting process requires the use of thread turning tools, thread cutters, etc. ; the rolling process requires the use of rolling heads and corresponding rolling tools. In addition, processing equipment such as lathes, milling machines and EDM machines are also required.
4. Processing accuracy and quality control The processing accuracy of internal threads has a significant impact on product quality and performance. Therefore, various parameters need to be strictly controlled during the processing process, such as pitch, tooth profile angle, surface roughness, etc. At the same time, regular quality checks are also necessary to ensure that the product meets the design requirements.
5. Selection of processing materials Processing materials for internal threads should be selected according to the use environment and product performance requirements. Common processing materials include steel, stainless steel, copper, aluminum, etc. When selecting materials, factors such as mechanical properties, corrosion resistance and wear resistance should be considered.
6. The internal thread calculation formula mainly includes the calculation of major diameter, minor diameter and pitch.
First of all, for the calculation of the small diameter of the internal thread, the formula can be expressed as follows: basic dimension of the small diameter = basic dimension of the internal thread – pitch × coefficient. Or, in some cases, the small diameter calculation may involve the bottom hole diameter. The calculation formula is: D hole = D-(1.05~1.1)P, where D hole is the small diameter of the internal thread. D is the nominal diameter of the thread and P is the pitch.
Second, for the calculation of the major diameter of the internal thread, the upper limit calculation formula is d-ges, that is, the basic size of the major diameter of the thread – reference deviation, the calculation formula of the lower limit is d-ges; -Td, i.e. the basic size of the large thread diameter – reference deviation – tolerance. Another formula to calculate the large diameter and small diameter is D=d+2P, where D represents the large diameter of the internal thread, d represents the small diameter of the internal thread, and P represents the pitch of the internal thread.
Finally, to calculate the pitch, the formula is: Pitch = 1 / TPI (Threads Per Inch), that is to say that the pitch is equal to the reciprocal of the threads per inch (TPI).
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