In the process of cone crusher operation, the bottom frame of crusher and the connecting bolt of motor received the stretching and shearing force from the crusher body and motor bracket. After long terms operation, it is easy to be worn, or even break, which will seriously affect the crusher normal production. Following, we will talk about the breaking reasons of the bolt.

1. Small contact surface of motor bracket and crusher bottom frame

High-strength bolt slides by the friction force between the contact surface of connecting parts. In order to get the enough friction force, it's necessary to improve the clamping force of connecting parts and increase the friction coefficient of the contact surface. If the contact surface is too small, it will cause relative slippage between motor bracket and crusher bottom frame, and generate huge shearing force at the bolt contact surface, resulting in the fracture of the bolt.

2. Clearance between motor bracket and crusher bottom frame

The connecting surface of motor bracket is slightly deformed due to the repeated bolt breakage, although the bolt reaches the fastening torque, the contact surface can appear gap, but will not produce impulse load. Motor bracket is also moving, which is easy to shear the bolt.

3. Bolt pretightening force does not meet the requirements

Tighten the nut of high-strength bolt by using torsion wrench. The large and controllable pretension force produced by bolt causes the same precompression for the connecting parts through nut and base plate. Under the function of precompression, the surface of the connecting parts will have a great friction force, the parts will not move and the connection will not be damaged. If the precompression varies, it could cause uneven force on the connecting surface, and thus breaking the bolt.