The processing methods of various threads are really getting better and better!

1. Thread cutting
Generally, it refers to the method of machining threads on workpieces using forming tools or grinding tools, mainly including turning, milling, tapping, threading, grinding, grinding, and whirlwind cutting. When turning, milling, and grinding threads, for each revolution of the workpiece, the transmission chain of the machine tool ensures that the turning tool, milling cutter, or grinding wheel moves accurately and uniformly along the axial direction of the workpiece by one lead. When tapping or threading, the tool (tap or die) rotates relative to the workpiece and is guided by the formed thread groove to move axially.
Turning threads on a lathe can be done using a forming tool or a thread comb (see threading tools). Turning threads with formed turning tools is a common method for producing threaded workpieces in single and small batches due to their simple structure; Turning threads with a thread comb cutter has high production efficiency, but the tool structure is complex and only suitable for turning short threaded workpieces with fine teeth in medium and large-scale production. The pitch accuracy of ordinary lathe turning trapezoidal threads can generally only reach levels 8-9 (JB2886-81, the same below); Processing threads on specialized thread lathes can significantly improve productivity or accuracy.
2. Thread milling
Use a disc milling cutter or comb milling cutter on a thread milling machine for milling. Disc milling cutters are mainly used for milling trapezoidal external threads on workpieces such as screw and worm. Comb shaped milling cutters are used for milling internal parts. Due to the use of external ordinary threads and tapered threads, multi edge milling cutters are used for milling, and the length of their working part is larger than the length of the processed thread. Therefore, the workpiece only needs to be rotated 1.25 to 1.5 revolutions to complete the machining, with high productivity. The pitch accuracy of thread milling can generally reach 8-9 levels, and the surface roughness is R5-0.63 micrometers. This method is suitable for mass production of thread work with general precision or rough machining before grinding.
3. Thread grinding
Mainly used for precision threading of hardened workpieces on thread grinding machines.
Thread grinding is divided into two types based on the different cross-sectional shapes of the grinding wheel: single line grinding wheel and multi line grinding wheel. The single line grinding wheel can achieve a pitch accuracy of 5-6 levels and a surface roughness of R1.25-0.08 micrometers, making the grinding wheel dressing more convenient.
This method is suitable for grinding precision screws, thread gauges, worms, small batch threaded workpieces, and precision hobs. Multi line grinding wheel grinding can be divided into two types: longitudinal grinding method and cut in grinding method. The width of the grinding wheel in the longitudinal grinding method is smaller than the length of the thread to be ground. The grinding wheel can be moved longitudinally once or several times to grind the thread back to the final size. The width of the grinding wheel in the cut in grinding method is greater than the length of the thread to be ground. The grinding wheel radially cuts into the surface of the workpiece, and the workpiece can be ground by about 1.25 revolutions. The productivity is high, but the accuracy is slightly low, and the grinding wheel dressing is relatively complex. The cutting in grinding method is suitable for grinding large batches of taps and grinding certain fastening threads.
4. Thread grinding
Use soft materials such as cast iron to make nut or screw type thread grinding tools, and perform forward and reverse rotation grinding on the parts of the workpiece where there is pitch error in the processed threads to improve pitch accuracy. Hardened internal threads are usually ground to eliminate variations and improve accuracy.
5. Tapping and threading
Tapping is the process of turning a tap into a pre drilled bottom hole on a workpiece with a certain torque to process internal threads.
Thread threading is the process of cutting external threads on a bar (or tube) workpiece using a die. The machining accuracy of tapping or threading depends on the accuracy of the tap or die. Although there are many methods for processing internal and external threads, small diameter internal threads can only be processed with a tap. Tapping and threading can be done manually, as well as using lathes, drilling machines, tapping machines, and threading machines.
6. Thread rolling
The processing method of obtaining threads by using forming and rolling molds to induce plastic deformation of the workpiece. Thread rolling is generally done on a thread rolling machine. Twisting machine or automatic lathe equipped with automatic opening and closing thread rolling head, suitable for mass production of external threads of standard fasteners and other threaded connectors.
The outer diameter of the rolled thread generally does not exceed 25 millimeters, the length does not exceed 100 millimeters, and the thread accuracy can reach level 2 (GB197-63). The diameter of all blanks is roughly equal to the pitch diameter of the processed thread. Rolling generally cannot process internal threads, but for workpieces with softer materials, slotless extrusion taps can be used to cold extrude internal threads (with a maximum diameter of about 30 millimeters), and the working principle is similar to tapping. The required torque for cold extrusion of internal threads is about twice that of tapping, and the machining accuracy and surface quality are slightly higher than tapping.
External thread rolling processing!
The advantages of thread rolling are:
1. The surface roughness is smaller than that of turning, milling, and grinding;
2. The surface of the thread after rolling can improve strength and hardness due to cold work hardening;
3. High material utilization rate; Productivity increases exponentially compared to cutting, and it is easy to achieve automation;
4. The service life of the rolling die is very long. But the rolling thread requires that the hardness of the workpiece material does not exceed HRC40;
5. High precision is required for the size of the blank;
6. The precision and hardness requirements for rolling molds are also high, making it difficult to manufacture molds;
7. Not suitable for rolling threads with asymmetric tooth shape.
According to different rolling molds, thread rolling can be divided into two types: thread rolling and thread rolling.
Rubbing silk
Two threaded thread plates are arranged in a staggered manner with a pitch of 1/2 relative to each other. The stationary plate is fixed, while the moving plate moves in a reciprocating linear motion parallel to the stationary plate. When the workpiece is fed between two plates, the moving plate advances and rubs the workpiece, causing its surface to undergo plastic deformation and form threads.
Rolling thread
There are three types of rolling: radial rolling, tangential rolling, and rolling head rolling. Radial thread rolling: Two (or three) threaded thread rolling wheels are installed on parallel axes, and the workpiece is placed on a support between the two wheels. The two wheels rotate in the same direction and at a constant speed.
One of the wheels also performs radial feed motion. The workpiece rotates under the drive of the thread rolling wheel, and the surface is subjected to radial compression to form threads. For certain screws with low precision requirements, a similar method of rolling forming can also be used. Tangential thread rolling: also known as planetary thread rolling, the rolling tool consists of one rotating central thread rolling wheel and three fixed arc-shaped thread plates.
When rolling, the workpiece can be continuously fed in, so the productivity is higher than that of rolling and radial rolling. Thread rolling head: It is performed on an automatic lathe and is generally used to process short threads on workpieces. The rolling head has 3-4 uniformly distributed wire rolling wheels around the periphery of the workpiece.
When rolling, the workpiece rotates and the rolling head feeds axially, rolling the workpiece out of the thread.