Impact wrench is a term that is frequently misused by those who don’t know the true definition of the tool. An impact wrench can be manually operated, or it can be powered by electricity or compressed air. An impact wrench powered by an air compressor is also known as a pneumatic wrench.

An impact wrench works in the manner suggested by the name of the tool: through the principle of impact. In order to understand how an electrical or air-powered impact wrench works, it helps to know first how a manually powered impact wrench operates. A manually powered impact wrench looks like a fat screwdriver; on the end where the screwdriver blade normally goes, you can snap on screwdriver bits or sockets.

To operate a manually powered impact wrench, fit the bit or socket onto the screw or bolt. Then hit the other end with a hammer while holding the wrench down. The inner workings of the wrench transform the downward impact into a turning motion, and the bolt is gradually loosened. This type of wrench works great, if a bit slowly, for breaking stiff or unyielding bolts loose.

An electrical or air-powered impact wrench works much the same way: when you pull the trigger, impact from tiny hammers inside the wrench is transformed into a rotary motion. The difference between one of these power tools and a manually powered impact wrench is that the tool does the work for you, and very quickly in comparison to the manual wrench.

Impact wrenches are often misused by those who don’t know about their special needs. First of all, it is very important to be careful when tightening a nut or bolt with an impact wrench! Cross threading can occur very easily; a novice may also over-torque a bolt or a nut if they don’t know when to stop. To prevent such problems, always be sure to hand-tighten every nut or bolt before using the impact wrench; if you try to start the nut or bolt with the impact wrench, you won’t be able to feel if the threads are crossed. If the impact wrench is not torque controlled – meaning it will stop when the nut or bolt is tightened to a certain torque – you will need to go slowly, and periodically check the torque value of the nut or bolt to make sure you haven’t tightened it too far.

An impact wrench also requires a few special accessories. An air-powered impact wrench runs off of an air compressor with a tank – the air compressor should have at least a 10 gallon tank and be able to generate at least 3hp. Also, an impact wrench requires special sockets that are designed to withstand the high torque applied by the wrench.

Although using an impact wrench requires a certain degree of expertise, it certainly makes the job easier, by cutting down on the amount of work and time required to get the job done. An impact wrench can even make changing a flat tire easier: some manufacturers make portable impact wrenches that plug into the cigarette lighter of your car and come with a variety of sockets to fit any size lug nut!