The electric wrench is powered by the motor. It can output torque smoothly and make accurate fixed torque. Moreover, the damage to the bolt is very small, but when the motor is overheated, it will affect the accuracy of its torque, and unsafe factors such as sparks will be generated when it is used in the assembly line, so the electric wrench is generally not used in the assembly line such as the engine.

气动扳手，风扳机，风炮。是空气推动气动马达，用敲击块做工的。它其实不是在转动，而是在不停的敲打螺母。所以噪声比较大，而且不能做到有效的定扭，并且会对螺栓有一定的危害，有时候会把螺栓打出裂纹来。

Pneumatic wrench, air trigger, air cannon. It is a pneumatic motor driven by air and made of percussion blocks. It's not actually turning, but beating the nut. Therefore, the noise is relatively large, and the effective fixed torque can not be achieved, and it will do some harm to the bolt. Sometimes the bolt will crack.

也有风动扳手可以做到平稳输出，精确认扭，很小的噪声，是失速型的风动扳手，它是风动马达带动一组齿轮组进行做工的，因为不是敲击，所以一般都要有一个反作用力臂。虽然有以上优点，但是速度比敲击扳手要慢。失速型扳手国外品牌象英国诺霸，阿做，但是很贵。

There are also pneumatic wrenches that can achieve stable output, accurate torque recognition and low noise. They are stall type pneumatic wrenches. They are made by a set of gear sets driven by a pneumatic motor. Because they are not percussion, they generally need a reaction force arm. Although it has the above advantages, the speed is slower than the knocking wrench. Stalling wrenches are made by foreign brands such as Norba in the UK and atlas, but they are very expensive.