Why did the tap break again? Is it a quality issue or a technical issue?

I believe that I have encountered the situation of tap breakage in machining. The editor will now come to analyze why your tap broke again. Please see the 9 reasons.

1. The tap quality is not good
Main materials, CNC tool design, heat treatment, machining accuracy, coating quality, etc. For example, the size difference at the transition of the tap cross-section is too large or the transition fillet is not designed to cause stress concentration, and it is easy to break at the stress concentration during use. The cross-section transition at the junction of the shank and the blade is too close to the weld, resulting in the superposition of complex welding stress and the stress concentration at the cross-section transition, resulting in a large stress concentration, which causes the tap to break during use. For example, improper heat treatment process. When the tap is heat treated, if it is not preheated before quenching and heating, quenching is overheated or over-burned, not tempered in time and cleaned too early, it may cause cracks in the tap. To a large extent, this is also an important reason why the overall performance of domestic taps is not as good as that of imported taps.
2. Improper selection of taps
For tapping parts with too much hardness, high-quality taps should be used, such as cobalt-containing high-speed steel taps, carbide taps, coated taps, etc. In addition, different tap designs are used in different work situations. For example, the number, size, angle, etc. of the chip flute heads of the tap have an impact on the chip removal performance.
3. The tap does not match the processed material
This problem has been paid more and more attention in recent years. In the past, domestic manufacturers always thought that imported products were good and expensive, but they were actually suitable. With the continuous increase of new materials and difficult processing, in order to meet this demand, the variety of tool materials is also increasing. This requires selecting a suitable tap product before tapping.
4. The hole diameter of the bottom hole is too small
For example, when machining ferrous metal M5×0.5 threads, the cutting tap should be used to make a bottom hole with a 4.5mm diameter drill bit. Add WeChat: Yuki7557 to send a macro program tutorial. If you use a 4.2mm drill bit to make a bottom hole, tap When threading, the part of the tap that needs to be cut will inevitably increase, which will cause the tap to break. It is recommended to choose the correct bottom hole diameter according to the type of tap and the material of the tapping piece. If there is no fully qualified drill bit, you can choose a larger one.
5. The problem of the material of the attacking parts
The material of the tapping piece is not pure, and there are hard spots or pores in some parts, which will cause the tap to lose its balance and break instantly.
6. The machine tool does not meet the accuracy requirements of the tap
The machine tool and clamping body are also very important, especially for high-quality taps, only a certain precision machine tool and clamping body can exert the performance of the tap. It is common that the concentricity is not enough. At the beginning of tapping, the starting position of the tap is incorrect, that is, the axis of the spindle is not concentric with the centerline of the bottom hole, and the torque is too large during the tapping process, which is the main reason for the breakage of the tap.
7. The quality of cutting fluid and lubricating oil is not good
Many domestic enterprises have begun to pay attention to this point. Many companies that have purchased foreign tools and machine tools have a very profound experience. There are problems with the quality of cutting fluid and lubricating oil, and the quality of processed products is prone to burrs and other adverse conditions. will also be greatly reduced.
8. Unreasonable cutting speed and feed
When there is a problem in processing, most domestic users reduce the cutting speed and feed rate, so that the propulsion force of the tap is reduced, and the thread accuracy of its production is greatly reduced, which increases the roughness of the thread surface, and the thread The hole diameter and thread accuracy cannot be controlled, and problems such as burrs are of course more unavoidable. However, if the feed speed is too fast, the resulting torque is too large and the tap is easily broken. The cutting speed during machine attack is generally 6-15m/min for steel; 5-10m/min for quenched and tempered steel or harder steel; 2-7m/min for stainless steel; 8-10m/min for cast iron. For the same material, the smaller the tap diameter takes the higher value, and the larger the tap diameter takes the lower value.
9. The operator’s technology and skills do not meet the requirements
The above problems all require operators to make judgments or give feedback to technicians, but at present, most operators in China do not pay enough attention. For example, when processing blind hole threads, when the tap is about to touch the bottom of the hole, the operator does not realize that the tap is still fed at the tapping speed before reaching the bottom of the hole, or the tap is broken due to forced feeding when the chip evacuation is not smooth. . It is recommended that operators strengthen their sense of responsibility.
It can be seen from the above that the reasons for the breakage of the tap can be described as various, including machine tools, fixtures, workpieces, processes, chucks and tools, etc. It is possible that the real reason may never be found just on paper. As a qualified and responsible tool application engineer, the most important thing is to go deep into the field, not just by imagination.