Design points of internal thread tools for wire thread inserts

Because the material processed by the internal thread of the wire thread insert is stainless steel. Generally, stainless steel has no hardness requirements, but it requires a hardness of HRC30~38, which increases its processing difficulty. When processing internal threads on stainless steel materials, especially when the hole diameter is small and the batch size is large, because the tap goes deep into the inner hole, a large number of cutter teeth participate in cutting at the same time. The tool not only contacts the workpiece in the cutting area, but also contacts the workpiece with its non-working side. , so that the friction and cutting force are very large, the tap cutting edge is not strong enough, and even the entire tap is not strong enough. This is especially true when processing small diameter fine threads.

In addition, the chip formation, discharge and heat dissipation conditions are very poor, especially the toughness of stainless steel materials and poor thermal conductivity. High thermal strength and strong chip adhesion. The tool is severely worn. In addition, stainless steel has a large linear expansion coefficient and a strong tendency to cool and harden, resulting in serious processing deformation. In addition, it is difficult for the coolant to enter the cutting area, and the cooling effect is poor. If it is not properly controlled, the tap will collapse or be "seized" in the threaded hole.

Because it is a blind hole, the transition section is less than 2 times the pitch, the tap cutting cone angle is large, and the cutting cone is short, which causes the tap teeth to have a heavy cutting load and makes the tap easy to break. It is easy to produce backcut when returning, further causing the tap to chip or break. Due to the need to compensate for the dimensional error of the wire sleeve surface, the accuracy of the thread is improved, and special tolerances with higher precision are given. Therefore, the accuracy of this kind of thread is 0.04mm higher than that of GBl97~81-4H, which will shorten the service life of the tap.

The locking wire thread sleeve can lock the screw in the threaded hole and prevent the screw from loosening when subjected to shock and vibration. It has better technological performance than ordinary locking devices. Compared with the inlaid steel or copper bushing method, under the same strength conditions, screws with smaller size and higher strength can be used, which can reduce the size and weight. The hardness of wire thread inserts is higher than that of screws, so there is less wear during the assembly and disassembly process of connecting with screws, and they can be used repeatedly. According to relevant experimental studies, the tensile strength of the wire thread insert is more than 7 times that of the screw, so the wire thread insert will not be damaged even if the screw breaks.