Because of the high engine power of engineering machinery and the strong impact load when it working which will cause strong vibrations, the common thread form of bolts and nuts will fall off on their own in such a strong impact vibration. In order to prevent the failure of fasteners caused by the vibration, fastener manufacturer has taken many anti-loosening measures, such as: chemical coating, nylon nuts, crushed nuts, preset torque nut, etc. These methods play a certain locking effect, but they have three common weaknesses:
          1)repeated use is poor, and some is even one-time, or less than 5 times;
        2) the installation and maintenance is inconvenient, loading and unloading the nuts need to go through several processes, and the work cost is very high;
        3) the chemical coating will pollute the environment, and construction workers may also cause occupational injuries.
        Using 30° variable tooth type locknuts, the locking effect is better, and loading and unloading the nuts is very convenience. It can be repeatedly used and do not pollute the environment, so it gradually applies to the key parts of the engineering machinery. In present the following parts of engineering machinery are using 30° variable tooth type locknut:

        Crane: steel connections, gear box, trolley tracks, spreader, cabinet and other parts.
        Excavators: spit broken hammer, rotary support, caterpillar band.
        Mixer: bracket, reducer base, tugs and other parts.
        Vibratory Rollers: universal joint of engine, the couplings.
        Dozer: caterpillar band, bucket, chassis.
        Loader: powertrain, chassis.