Deep hole thread processing of the hottest special

Deep hole thread machining of special material parts (Part 1)

deep hole thread machining of special material parts is relatively difficult. For example, deep hole tapping on a titanium alloy part is very challenging. It is very uneconomical to scrap a part that is close to completion due to the scraping effect caused by the broken tap

therefore, in order to avoid scraping, it is required to use correct cutting tools and tapping technology. The reasons can be found and solved from the above four aspects

first of all, we need to define what is deep hole and why it needs special consideration. In drilling, those holes with a depth greater than 3 times the aperture are called deep holes, which is 54% higher than the current one. Deep hole tapping means modernization, which means that the tapping depth is more than 1.5 times of the tap diameter. For example, when a tap with a diameter of 1/4 is used to process a thread with a depth of 3/8, this situation is usually called deep hole tapping

machining a deep hole thread means that the tool needs a long time of contact with the workpiece. At the same time, more cutting heat and greater cutting force will be generated in the machining process. Therefore, tapping in small deep holes of special materials (such as titanium parts) is prone to tool damage and thread inconsistency

to solve this problem, two schemes can be adopted: (1) increase the diameter of the hole before tapping; (2) Use a tap specially designed for deep hole tapping

1. Increasing the diameter of the hole before tapping is very important for thread machining. A slightly larger threaded bottom hole can have an export share to emerging countries, which will also greatly improve the efficiency and reduce the cutting heat and cutting force generated in the tapping process. But it also reduces the thread contact rate

the national standards and Technical Committee stipulates that in deep holes, only 50% of the full height of the thread is allowed to be punched on the hole wall. This is particularly important when tapping holes in special materials and difficult to machine materials. Because although the thread contact rate decreases due to the reduction of the thread height on the hole wall, the reliable connection of the thread can still be maintained due to the increase of the thread length

the diameter increment of thread bottom hole mainly depends on the required thread contact rate and the number of thread heads per inch. According to the above two values, the correct diameter of threaded bottom hole can be calculated by using empirical formula

2. Cutting parameters

because titanium parts are difficult to machine, it is necessary to fully consider the cutting parameters and tool geometry