In the percussion drilling system, one end of rock drill bit is connected to drill rod through a joint to obtain the impact energy of rock drill; the other end collides with the rock in the blast hole, and the impact drilled the rock. During rock drilling, part of the impact energy is transmitted to the rock in the form of stress waves for rock breaking; another part of the impact energy is reflected at the shank adapter in the form of stress waves and is consumed in the rock drilling tools, resulting in fatigue damage to rock drilling tools. So, what are the joint forms of traditional rock drill bits?

In the percussion drilling system, the connection forms of a traditional rock drill bit and drill rod are tapered connection, CS sleeve connection, and MF thread connection.

1. Tapered connection

When the rock drill bit with a tapered hole and the drill rod with a tapered body is connected by a tapered, the inner tapered surface of rock drill bit taper hole and the outer tapered surface of drill rod tapered are pressed against each other by the friction between the inner and outer surfaces, the bottom surface of rock drill bit taper hole is suspended, and the inner tapered surface of rock drill bit taper hole is the bearing surface.

2. CS sleeve connection

When the rock drill bit with male thread and the drill rod with male thread are connected by a CS sleeve, the top surface of male thread of rock drill bit and the top surface of the male thread of the drill rod are tightened by a CS sleeve, and the bottom surface of the empty tool groove at the end of the male thread of rock drill bit is overhung, and the top surface of the male thread of rock drill bit is the carrying surface.

3. MF thread connection

When the rock drill bit with female thread and the drill rod with male thread are connected by MF thread, the bottom end surface of the female thread of rock drill bit and the top surface of the male thread of drill rod are tightened by MF thread, and the bottom surface of the female thread of rock drill bit is suspended, the bottom end surface of the empty slit at the end of the female thread of rock drill bit is the bearing surface.

All three forms of rock drill bit connections gather energy at the center of the bearing surface. At the moment when the rock drill drills into the rock to do work, the stress wave either along the inner taper of the tapered hole of rock drill bit (tapered connection) or along the top of rock drill bit male thread (CS sleeve connection) or the bottom surface of the empty tool groove at the end of the female thread of rock drill bit (MF thread connection), the vertical incident point occurs at the center of rock drill bit, and oblique incidence occurs at other parts. In this way, the rock drilling energy obtained per unit blade length of rock drill bit is the largest at the center point along the radial direction of rock drill bit, gradually decreases with the increase of the distance from the center point, and is the smallest at the periphery. Therefore, the rock drilling energy distribution obtained per unit edge length of rock drill bit is large in the middle and small in the periphery.