Types of Thread Manufacturing Processes Commonly Used in CNC Lathe Processing - Thread Manufacturing Methods

Threading is one of the important applications of CNC machining. The processing quality and efficiency of the thread will directly affect the production efficiency of the processing quality of the parts. Several commonly used thread manufacturing methods are summarized below. How to reasonably choose the wire making method in processing to improve production efficiency?

Types of thread manufacturing processes - thread manufacturing methods

1. Thread cutting

Usually refers to the method of machining threads on workpieces with forming tools or abrasives, mainly including turning, milling, tapping, threading, grinding, grinding and whirling. When turning, milling and grinding threads, the machine tool's drive chain ensures that the turning tool, milling cutter or grinding wheel moves the wire accurately and evenly in the axial direction of the workpiece. During tapping or tapping, the tool (tap or die) rotates relative to the workpiece, and a thread groove is formed that guides the tool (or workpiece) to move axially.

2. Thread turning

Form turning tools or thread combs can be used to turn threads on a lathe. Due to its simple structure, thread turning with a forming turning tool is a common method for single-piece small batch production of threaded workpieces; thread turning with a thread comb has high production efficiency, but the tool structure is complex. It is only suitable for medium and high volume production of short thread workpieces with medium turning fine pitch. The pitch accuracy of ordinary lathes for turning trapezoidal threads can only reach 8 to 9 grades. When threading on a dedicated thread lathe, productivity or precision can be significantly improved.

3. Thread milling

Milling is performed on a thread milling machine with a disc cutter or a comb cutter. Disc milling cutters are mainly used for milling trapezoidal external threads on workpieces such as screws and worms. Comb cutters are used for milling internal and external common threads and tapered threads. Since it is milled with a multi-blade milling cutter, and the length of its working part is greater than the length of the thread to be machined, it only needs to rotate 1.25 to 1.5 turns to machine the workpiece, and the productivity is very high. The pitch accuracy of thread milling can generally reach 8 to 9 grades, and the surface roughness is R5 to 0.63 microns. This method is suitable for mass production of general precision threaded workpieces or rough machining before grinding.

4. Thread grinding

Mainly used for threading of hardened workpieces on thread grinding machines. According to the cross-sectional shape of the grinding wheel, it can be divided into single-line grinding wheel and multi-line grinding wheel. The pitch accuracy of the single-line grinding wheel is 5 to 6, and the surface roughness is R1.25 to 0.08 μm, which is more convenient for grinding wheel dressing. This method is suitable for grinding screws, thread gauges, worms, small batches of threaded workpieces and relief grinding hob. Multi-line grinding wheel grinding is divided into longitudinal grinding method and plunge grinding method. The width of the grinding wheel in the longitudinal grinding method is smaller than the length of the thread to be ground. Threads can be ground to size by moving the wheel longitudinally one or more times. In plunge grinding, the width of the grinding wheel is greater than the length of the thread to be ground. The grinding wheel cuts radially into the workpiece surface and can grind the workpiece after about 1.25 revolutions. Productivity is high, but accuracy is slightly lower, and wheel dressing is more complex. Plunge grinding is suitable for shoveling and grinding a large number of taps and for grinding some threads for tightening.

5. Tapping and threading

Tapping is to screw the tap into the pre-drilled bottom hole on the workpiece with a certain torque to process the internal thread. Threading is the use of a die to cut an external thread on a bar (or pipe) workpiece. The machining accuracy of tapping or tapping depends on the accuracy of the tapping or die. Although there are many ways to machine internal and external threads, small diameter internal threads can only be machined with a tap. Tapping and tapping can be performed manually or using lathes, drill presses, tapping machines and tapping machines.