1. Tap quality is poor, quality is not good
The main materials, CNC tool design, heat treatment, processing accuracy, coating quality, etc., such as the size difference at the transition of the tap section is too large or the transition fillet is not designed, resulting in stress concentration, and it is easy to break at the stress concentration in use. The cross section transition at the joint of the shank and the blade is too close to the weld, resulting in complex welding stress superimposed with the stress concentration at the cross section transition, resulting in a large stress concentration, resulting in the tap breaking during use. For example, the heat treatment process is improper. In the heat treatment process of the tap, if the tap is not preheated before quenching heating, quenching overheating or over-burning, tempering is not timely, and cleaning is too early, it may lead to cracks in the tap. To a large extent, this is also a key reason why the overall performance of domestic taps is not as good as that of imported taps.
2. Improper tap selection
For tapping parts with excessive hardness, high-quality taps should be selected, such as high-speed steel taps containing cobalt, cemented carbide taps, coated taps, etc. In addition, different workplaces use different tap designs. For example, the number, size and Angle of the tap chute affect the chute performance
3. Mismatch between tap and machining material
In recent years, this problem has attracted more and more attention. In the past, domestic manufacturers have always thought that imported is good and cheap is bad, but it is actually appropriate. With the increasing number of new materials and processing difficulties, in order to meet this demand, the variety of tool materials is also increasing. This requires selecting the appropriate tapping product before tapping
4. The bottom hole aperture is too large
For example, when machining the black metal material M5 x cutting 0.5 threads, a bit with a diameter of 4.5mm should be used as the base. If the 4.2mm drill bit is used for bottoming, the cutting part of the tap must be increased when tapping, which will break the tap. It is recommended to select the exact bottom hole diameter according to the tap type and tap part material. If a fully compatible drill bit is not available, a larger drill bit can be selected
5. Tapping material problem
Tapping sheet material is not pure, some positions have hard points or pores, resulting in instant loss of balance, resulting in tapping fracture
6. The machine does not meet the accuracy requirements of the tap
Machine tools and grippers are also very critical, especially for high-quality taps, and only machines and grippers with a certain precision can play the performance of the tap. Often, concentricity is not enough. At the beginning of tapping, the start and positioning of the tap are not accurate, that is, the spindle axis is different from the center line at the bottom of the hole, and the torque is too large when tapping, which is the main reason for the tap fracture
Seven. The quality of cutting fluid and lubricating oil is not good
Many domestic enterprises are beginning to pay attention to this. Many companies that buy foreign tools and machine tools have very rich experience. There are problems in the quality of cutting fluid and lubricating oil, and the quality of processed products is prone to bad situations such as burrs, and the service life will be greatly reduced
8. The cutting speed and feed speed are inappropriate
When there is a problem in processing, most users in the country reduce the cutting speed and reduce the feed speed, reduce the push force of the tap, and the thread accuracy will be greatly reduced. In this way, the surface roughness of the thread increases, the diameter of the thread and the precision of the thread can not be controlled, and the problems such as burrs are of course more inevitable. However, if the feed speed is too fast, the excessive torque is easy to break the tap. The cutting speed when tapping, the general steel material is usually 6-15m/min; Tempered steel or hard steel is 5-10m/min; Stainless steel is 2-7m/min; Cast iron is 8-10m/min. For the same material, the tap diameter is large, the lower the value, the smaller the tap diameter, the higher the value