1. Poor quality of taps:

Main materials, tool design, heat treatment, processing accuracy, coating quality, etc. For example, the size difference at the transition of the tap section is too large or there is no transition fillet designed, which leads to stress concentration, and it is easy to break at the stress concentration point during use. The cross-sectional transition at the junction of the handle and the blade is too close to the weld, resulting in the superposition of complex welding stress and stress concentration at the cross-sectional 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, overheated or overburned during quenching, untimely tempering and premature cleaning may cause cracks in the tap. 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 high hardness, high-quality taps should be selected, such as cobalt-containing high-speed steel taps, carbide taps, coated taps, etc. In addition, different tap designs are used in different working occasions. For example, the number, size, angle, etc. of the chip removal grooves of the tap have an impact on the chip removal performance.

3. The tap does not match the material being processed:

This issue has received more and more attention in recent years. In the past, domestic manufacturers always thought that imported materials were good and expensive, but in fact, suitable materials were good. With the continuous increase and difficulty in processing new materials, in order to meet this need, the variety of tool materials is also increasing. This requires choosing a suitable tap product before tapping.

4. The bottom hole diameter is too small:

For example, when processing the M5×0.5 thread of ferrous metal materials, a 4.5mm diameter drill should be used to drill the bottom hole with a cutting tap. If a 4.2mm drill is used to drill the bottom hole by mistake, the part that the tap needs to cut during tapping 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 drill bit that fully matches the requirements, you can choose a larger one.

5. Tap material problem:

The tap material is impure, and there are local hard points or pores, which causes the tap to lose balance and break instantly.

6. The machine tool does not meet the precision requirements of the tap:

The machine tool and the clamping body are also very important, especially for high-quality taps. Only machine tools and clamping bodies with a certain precision can bring out the performance of the tap. The most common problem is insufficient concentricity. At the beginning of tapping, the tap is not positioned correctly, that is, the spindle axis is not concentric with the center line of the bottom hole, and the torque is too large during the tapping process. This is the main reason for the tap breaking.

7. Poor quality of cutting fluid and lubricating oil:

Many domestic enterprises have begun to pay attention to this point. Many companies that have purchased foreign tools and machine tools have a very deep understanding that if there are problems with the quality of cutting fluid and lubricating oil, the quality of the processed products is prone to burrs and other undesirable conditions, and the service life will also be greatly reduced.

8. Unreasonable cutting speed and feed rate:

When problems occur in processing, most domestic users reduce the cutting speed and feed rate, so that the advancement force of the tap is reduced, and the thread accuracy is greatly reduced, which increases the roughness of the thread surface, and the thread diameter and thread accuracy cannot be controlled. Burrs and other problems are of course more inevitable. However, if the feed speed is too fast, the resulting excessive torque can easily cause the tap to break. The cutting speed during machine tapping is 6-15m/min for general steel, 5-10m/min for quenched and tempered steel or harder steel, 2-7m/min for stainless steel, and 8-10m/min for cast iron. For the same material, a higher value is used for a smaller tap diameter and a lower value is used for a larger tap diameter.

9. The operator's technology and skills do not meet the requirements:

All of the above problems require the operator to make judgments or feedback to the technical staff, but most domestic operators currently do not pay enough attention to them. For example, when processing blind hole threads, when the tap is about to touch the bottom of the hole, the operator does not realize it and still feeds at the tapping speed before reaching the bottom of the hole, or feeds forcefully when chip removal is not smooth, causing the tap to break. It is recommended that operators strengthen their sense of responsibility.

As can be seen from the above, there are many reasons for the breakage of taps, including machine tools, fixtures, workpieces, processes, chucks and tools, etc. It may never be possible to find the real reason just by talking about it on paper.