The commonly used thread types are: corrugated thread, anti sawtooth thread and trapezoidal thread. The direction of rotation of the thread is left (that is, opposite to the direction of rotation of the rotary mechanism of the rock drill). Figure 3-5 shows the drill bit for cone connection. The connection belongs to interference fit. The cone of the breaking hammer drill rod is pressed into the taper hole of the drill bit, and the friction force of the contact surface is used to transfer the impact force and torque, so that the two will not loose and slip. The cone connection is easy to process and durable, so it is widely used for small diameter drill bits.

The parameters and accuracy of cone connection have an important influence on the connection quality. The smaller the cone angle, the better the connectivity, but the worse the disassembly; On the contrary, the larger the cone angle is, the better the disassembly is, but the worse the connectivity is, the bit is easy to fall off in use In addition, the connectivity and dismantlement of the cone angle are also related to the rock firmness and the impact energy of the rock drill. According to the national standard GB/T 6480-1994, 4.8 shall be adopted if the drill bit diameter is less than or equal to 35mm. Taper angle: 70 for drill bits with a diameter of 36~43mm and 120 for drill bits with a diameter of more than 45mm. It is basically the same as the international standard ISO 1718-1991.

The connection between the breaking hammer bit and the breaking hammer bit shall meet the following requirements: the removal and installation of the bit shall be simple and convenient, easy to process and manufacture, the connection shall be firm and reliable, and the energy transmission efficiency shall be high. The common connection forms of the breaking hammer bit include threaded connection and cone connection.

The structure of the broken hammer drill bit with thread connection can be divided into two types: (1) The drill bit has male (external) threads and is connected with the broken hammer drill rod with a connecting sleeve; (2) The drill bit has a female (internal) thread and is directly connected with the breaking hammer drill rod with a male (external) thread. The latter is used more often, as shown in Figure 3-4. The structural feature is that the pitch diameter of female thread is slightly larger than that of male thread If the gap is more than 25mm, it can be deformed under the impact force