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.

氣動扳手，風(fēng)扳機，風(fēng)炮。是空氣推動氣動馬達，用敲擊塊做工的。它其實不是在轉(zhuǎn)動，而是在不停的敲打螺母。所以噪聲比較大，而且不能做到有效的定扭，并且會對螺栓有一定的危害，有時候會把螺栓打出裂紋來。

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.

也有風(fēng)動扳手可以做到平穩(wěn)輸出，精確認扭，很小的噪聲，是失速型的風(fēng)動扳手，它是風(fēng)動馬達帶動一組齒輪組進行做工的，因為不是敲擊，所以一般都要有一個反作用力臂。雖然有以上優(yōu)點，但是速度比敲擊扳手要慢。失速型扳手國外象英國諾霸，阿特拉斯做，但是很貴。

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.