Turning technology of copper nut threads: There are two kinds of methods to process internal and external threads on the workpiece: cutting and rolling.

The application of threading principle can be traced back to the spiral water lifting tool created by Greek scholar Archimedes in 220 B.C. In the 4th century AD, the Mediterranean coastal countries began to apply the principle of bolts and nuts to wine-making presses. At that time, the external threads were made by twisting a rope around a cylindrical bar and then carving according to this mark. The inner thread is usually formed by hammering around the outer thread with softer material. Around 1500, Italian Leonardo Da Vinci drew a sketch of thread processing equipment, and there was an idea of using nut screw and exchange gear to process different pitch threads. Thereafter, the method of mechanical cutting threads has developed in the European watch manufacturing industry. In 1760, the British brothers J. Wyatt and W. Wyatt obtained a patent for cutting wooden screws with special devices. In 1778, J. Ramsden, an Englishman, manufactured a thread cutting device driven by worm gears to produce long threads with high accuracy. In 1797, H. Mozley, an Englishman, developed a basic method of turning threads by turning metal threads with different pitches on his improved lathe with nut screw and switching gear. In the 1920s, Mozley produced the first batch of taps and plate teeth for thread processing. At the beginning of the 20th century, the development of automobile industry further promoted the standardization of thread and the development of various precision and efficient thread processing methods. Various automatic opening plate tooth heads and automatic shrinkage taps were invented one after another, and thread milling began to be applied. In the early 1930s, thread grinding appeared. Thread rolling technology was patented in the early 19th century, but it developed very slowly because of the difficulties in die manufacturing. It was not until the Second World War (1942-1945) that the precision problem of die manufacturing was solved by the development of arms production and thread grinding technology.

1) Thread cutting generally refers to the method of processing threads on workpieces with forming tools or abrasives, including turning, milling, tapping, threading, grinding, grinding and whirlwind cutting. When turning, milling and grinding threads, the transmission chain of the machine tool ensures that the turning tool, milling cutter or grinding wheel can move a guide accurately and evenly along the axis of the workpiece with each turn of the workpiece. When tapping or sleeving, the tool (tap or plate tooth) rotates relative to the workpiece, and the tool (or workpiece) is guided by the thread groove formed first to move axially. Thread turning (thread turning) In turning threads on lathes, forming turning tools or thread combing tools can be used (see thread processing tools). Because of the simple structure of the tool, turning threads with shaped turning tools is a common method for single-piece and small-batch production of threaded workpieces; turning threads with threaded comb tools has high production efficiency, but the structure of the tool is complex, so it is only suitable for turning short threaded workpieces with fine teeth in medium and large-scale production. Generally speaking, the pitch accuracy of trapezoidal thread turning on ordinary lathe can only reach 8-9 grades (JB2886-81, the same below); when thread is processed on specialized thread lathe, productivity or accuracy can be significantly improved.

2) Thread milling (thread milling) in the thread milling machine with disc or comb milling cutter for milling. Disc milling cutter is mainly used for milling trapezoidal external threads on workpieces such as screw and worm. Comb milling cutter is used to milling internal and external common thread and taper thread. Because it is milling with multi-edge milling cutter and the length of its working part is longer than the length of the thread being processed, the workpiece can be processed only by rotating 1.25-1.5 revolutions with high productivity. The pitch accuracy of thread milling can generally reach 8-9 grades, and the surface roughness is R 5-0.63 microns. This method is suitable for mass production of threaded workpieces with general accuracy or rough machining before grinding.

3) Thread grinding is mainly used to process the precise threads of hardened workpiece on the thread grinder. It can be divided into single-line grinding wheel and multi-line grinding wheel according to the cross-section shape of grinding wheel. The pitch accuracy of single-line grinding wheel is 5-6 grade, and the surface roughness is R 1.25-0.08 micron. It is convenient for grinding wheel dressing. This method is suitable for grinding precision screw, thread gauge, worm, small batch thread workpiece and relief grinding precision hob. Multi-line grinding wheel can be divided into longitudinal grinding method and cut-in grinding method. The width of the grinding wheel in the longitudinal grinding method is less than the length of the threads being ground. The threads can be grinded to the final size by moving the wheel once or several times in the longitudinal direction. The grinding wheel width of cut-in grinding method is larger than the length of the thread being ground. When the grinding wheel cuts into the surface of the workpiece radially, the workpiece can be grinded at about 1.25 revolutions, and the productivity is higher, but the precision is slightly lower, and the dressing of the grinding wheel is more complicated. The cut-in grinding method is suitable for relieving large batches of taps and grinding some fastening threads.

4) Thread grinding tools made of soft materials such as cast iron are used to grind threads of nut type or screw type. The parts with pitch errors of threads processed on workpieces are grinded by forward and backward rotation in order to improve pitch accuracy. Hardened internal threads are usually ground to eliminate deformation and improve accuracy.

5) Tapping and sleeve tapping (tapping with taps) is to use a certain torque to spin the tap into the pre-drilled bottom hole on the workpiece to produce internal threads. Sleeve (plate tooth sleeve) is the use of plate teeth in bar (or pipe) workpiece to cut out the external threads. The processing accuracy of tapping or sleeve depends on the accuracy of tap or plate teeth. Although there are many ways to process internal and external threads, small diameter internal threads can only be processed by taps. Tapping and threading can be operated by hand or by lathes, drills, tappers and threading machines.

6) The forming rolling die is used for thread rolling to produce plastic deformation of the workpiece to obtain the processing method of the thread. Thread rolling is usually done on the screw rolling machine. Thread rubbing machine or automatic lathe with automatic opening and closing thread rolling head