Thread processing is an important process in mechanical manufacturing and is widely used in fastening, transmission and other fields. According to different processing methods, it can be divided into thread cutting, thread grinding, thread grinding, tapping and threading, and thread rolling. Different processing methods are suitable for different materials, precision requirements and production batches. Reasonable selection of processing methods can effectively improve production efficiency and product quality.
Thread cutting
Thread cutting is a processing method that uses forming tools or grinding tools to remove materials to form threads, mainly including turning, milling, tapping, threading, grinding and whirlwind cutting. When turning threads, the transmission chain of the machine tool ensures that the tool moves evenly along the axial direction of the workpiece for one lead, thereby forming an accurate thread profile.
Using forming turning tools for turning is suitable for single-piece or small-batch production, while using thread combing tools is suitable for batch production of short-threaded workpieces, which can improve processing efficiency. Trapezoidal threads usually require special thread lathes to ensure higher processing accuracy and efficiency.
Thread milling
Thread milling is mainly carried out on thread milling machines, using disc end mills or comb milling cutters for processing. Disc milling cutters are suitable for processing trapezoidal threads, such as lead screws and worms, while comb milling cutters are suitable for processing ordinary external threads and tapered threads.
Since multi-edge thread cutting end mills can complete the processing of the entire thread within a shorter rotation angle, thread milling has a higher production efficiency. Usually, this method is used for mass production of ordinary precision threaded workpieces, or as a pre-processing process before thread grinding to reduce the workload of subsequent finishing.
Thread grinding
Thread grinding is suitable for precision thread processing of hardened workpieces, and is usually carried out on thread grinders. According to the cross-sectional shape of the grinding wheel, it can be divided into single-line grinding wheel grinding and multi-line grinding wheel grinding. Although single-line grinding wheel grinding is easy to dress, its production efficiency is relatively low. Its pitch accuracy can reach 56 levels, and its surface roughness can reach R1.250.08 microns.
It is suitable for the processing of workpieces such as precision lead screws and thread gauges. Multi-line grinding wheel grinding uses longitudinal grinding or plunge grinding, among which the plunge grinding method is more efficient and suitable for mass-produced taps and certain fastening threads.
Thread grinding
Thread grinding uses a softer nut-type or screw-type grinding tool to perform forward and reverse rotation grinding on the processed thread to eliminate pitch error and improve thread accuracy. This method is mostly used for precision internal thread processing of hardened workpieces, especially the final correction of high-precision threads. Grinding can effectively reduce thread deformation and improve matching accuracy. It is often used in precision machinery, measuring instruments and other fields.
Tapping and threading
Tapping is used to process internal threads. It is necessary to drill a bottom hole on the workpiece first, and then screw in the tap to form a thread. Threading is to use a die to cut an external thread on a bar or tube. The processing accuracy mainly depends on the quality of the tap or die, which is suitable for the processing of small diameter threads. Tapping and threading can be done manually, or with the help of a lathe, drilling machine, tapping machine or threading machine to improve production efficiency and ensure thread quality.
Thread rolling
Thread rolling is a processing method that forms threads through plastic deformation, usually on a thread rolling machine, a thread rolling machine or an automatic lathe with a rolling device. This method is suitable for mass production of standard fasteners and threaded connectors, and the thread rolling can obtain higher strength and surface quality. The outer diameter of the rolled thread is generally not more than 25mm, the length is not more than 100mm, and the accuracy can reach level 2 of the GB197-63 standard. Although rolling is mainly used for external thread processing, for softer materials, a slotless extrusion tap can also be used for cold extrusion of internal threads. Its accuracy and surface quality are better than traditional tapping, but the required torque is larger.
There are many different thread processing methods, from traditional cutting to high-efficiency rolling, each with its own scope of application. Choosing the right processing method requires comprehensive consideration of the workpiece material, thread accuracy, production batch and processing cost. For high-precision threads, it is often necessary to use a variety of methods, such as milling or turning first, and then grinding or grinding to ensure the final quality. The rational use of these processing methods can improve production efficiency, reduce processing costs, and meet the needs of different application scenarios.
