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What Are The 9 Major Reasons For Tap Breaks
Feb 13, 2019

What are the 9 major reasons for tap breaks?


1. The quality of the tap is not good:


Main materials, tool design, heat treatment, machining accuracy, coating quality, etc.


For example, the difference in size of the transition of the tap section is too large or there is no design transition fillet to cause stress concentration, and it is easy to break at the stress concentration during use.


The cross-section transition at the intersection of the shank and the blade is too close to the weld, resulting in a complex weld stress superimposed on the stress concentration at the cross-section transition, resulting in a large stress concentration, causing the tap to break during use.


For example, the heat treatment process is improper. When the tap is heat treated, if it is not preheated before quenching and heating, quenching is overheated or overheated. If it is not tempered in time and the cleaning is too early, it may cause cracks in the tap. This is also an important reason why the overall performance of domestic taps is not as good as imported taps.


2. The tap is not properly selected:


For high-strength tapping parts, high-quality taps, such as cobalt-containing high-speed steel taps, hard alloy taps, coated taps, etc., should be used.


In addition, different tap designs are used in different work situations. For example, the number of taps, the size, the angle, etc. of the tap have an effect on the chip removal performance.


3. The tap does not match the processed material:


This problem has received more and more attention in recent years. In the past, domestic manufacturers always felt that the import was good and the price was good. In fact, it was suitable.


As new materials continue to increase and are difficult to machine, the variety of tool materials is constantly increasing to accommodate this need. This requires selecting the right tap product before tapping.


4. The bottom hole diameter is too small:


For example, when machining a black metal material M5×0.5 thread, the cutting tap should use a 4.5 mm diameter drill bit to make a bottom hole. If a 4.2 mm drill bit is misused to make a bottom hole, the cutting part of the tap must be increased when tapping. And then break the tap.


It is recommended to select the correct bottom hole diameter according to the type of tap and the material of the tapping piece. If the drill bit is not fully matched, you can choose a larger one.


What is the bottom hole for tapping? Click here to download HD PDF "Tapping bottom hole comparison table" for free

5. Attack material problem:


The material of the attack piece is not pure, and there are too hard points or stomata in the part, which causes the tap to lose balance and break.


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


Machine tools and clamping bodies are also very important, especially for high-quality taps, as long as the precision of the machine and the clamping body can play the performance of the tap. It is common that the concentricity is not enough.


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, which is the main reason for the tap breaking.


7. Cutting fluid, the quality of lubricating oil is not good:


Many domestic enterprises have begun to pay attention to it. Many companies that have purchased foreign tools and machine tools have a very deep understanding. The cutting fluids and lubricants have problems in quality. The quality of the processed products is prone to burrs and other life. There will also be a big reduction.


8. Cutting speed and feed rate are unreasonable:


When there is a problem in processing, most domestic users are reducing the cutting speed and reducing the feed rate, so that the pushing force of the tap is reduced, and the thread precision of the production is greatly reduced, thus increasing the roughness of the thread surface, the thread. Aperture and thread accuracy are uncontrolled, and problems such as burrs are of course more inevitable.


However, the feed speed is too fast, and the resulting excessive torque is also likely to cause the cutting speed when the tap breaks the machine. The general steel material is 6-15 m / min; the quenched and tempered steel or the harder steel material is 5-10 m / Minutes; stainless steel is 2-7m / min; cast iron is 8-10m / min.


In the same material, the diameter of the tap is smaller and the diameter of the tap is larger.


9. Operator skills 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 at present most of the operators in China do not pay enough attention.


For example, when machining a blind hole thread, when the tap is about to contact the bottom of the hole, the operator does not realize that it is still fed at the tapping speed when it is not at the bottom of the hole, or forcibly feeding when the chip is not smooth, causing the tap to break. . It is recommended that operators strengthen their sense of responsibility.


It can be seen from the above that there are many reasons for the breakage of the tap. Machine tools, fixtures, workpieces, crafts, chucks and knives are all possible. It is possible to find the real reason only on paper.


As a qualified and responsible tool application engineer, the most important thing is to go deep into the field, not just imagine.


For the simplest example, if the length of the tap cutting cone is too long, it will break when hitting the bottom of the bottom hole during tapping. If you don't go into the field, just guess the tap performance, workpiece material, processing technology, etc.? I couldn't think of dreaming at the beginning, but there are customers who have experienced such problems that you might think are extremely low-level, but you have to face it.


In fact, neither the traditional tapping equipment nor the expensive numerical control equipment can solve the above problems in principle. Because the machine does not recognize the tap's operating conditions and the most appropriate torque required, it will only repeat the machining based on pre-set parameters. The failure is only found when the machined part is finally detected with a thread gauge, and it is too late to find it.


Even if it was found, it was useless. The scrapped and expensive parts had to be scrapped, and the unqualified products had to be thrown into the defective products.


Therefore, in large enterprises for large, expensive, and precise workpiece processing, even the imported taps are not domestically produced, because once the tap is broken, the workpiece is scrapped, and the cost is considerable.


Foreigners are awkward, and the price of taps is high. Whenever a considerable portion of the profits of a company are taken by foreigners, it is not sad. Hey, the Chinese still need to work hard!


HANGZHOU XIAOSHAN HUAGONG TOOLS FACTORY

Add: Zhejiang  Hangzhou Xiaoshan Suoqian Industry Zone

Tel: +86-571-82347868

Fax: +86-571-82345081

E-mail: hgtools@hgtools.com


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