What’s this page about? The impact wrench and…

  • what it is and how an impact wrench works
  • how to size an impact wrench
  • how to buy an impact wrench

What is an impact wrench?

An impact wrench, this one manufactured and sold buy Ingersoll Rand

An air operated impact wrench, this one  sold by Ingersoll Rand

An impact wrench could be considered as a socket wrench on steroids and have been around a long time.

To use a socket wrench the operator attaches a ratchet handle to the socket and by manually rotating the handle, the socket is driven in a clockwise or anti-clockwise direction to thread on or thread off something, be it a bolt into a nut, or a nut onto a threaded shaft… etc etc.

Occasionally it requires more torque (turning force) to loosen a bolt or a nut than the operator can provide using arm strength. A ratchet extension can be used sometimes to allow more torque to be applied manually, but sometimes the object to be loosened cannot be broken free manually.

Enter the impact wrench. The impact wrench takes most of the work out of turning the socket while the “impact” part of the impact wrench imparts greater force into rotating the socket than a person can and it can quickly break free stubborn bolts and nuts allowing them to be threaded off and on easily and with speed.

Impact Wrench Innards!

So, what’s inside the basic impact wrench? How does the impact wrench work?

The basics are that and impact wrench is operated like any air tool. An air supply entering the impact wrench will force the rotational movement of vanes inside the tool, which will rotate the spindle, like an air drill, for example.

But then, a clever arrangement of springs, cams, an anvil and a hammer turn that rotational force into impact force, slamming into and turning the socket with speed and force.

Here’s a look at how they work in a video found on www.popularmechanics.com.

Can an impact wrench be run by any air compressor?

The short answer is yes, it can, as long at the pressure delivered by the compressor is greater than the minimum operating pressure of the impact wrench being used.

However, if the compressor doesn’t generate enough air flow to feed the socket wrench, even at the right pressure, eventually the socket wrench will lack sufficient air to run, and it will stop. That’ll happen usually in the middle of removing a nut!

Don’t stress it if that happens. Stop using the wrench and wait for the compressor to catch up, filling the tank up to cut out, and then when the compressor stops again, there will be enough pressure and flow to run the wrench for a while again.

Commercial impact wrenches

If the intent is to acquire an impact wrench to use commercially, in a garage for example, care must be taken to ensure that the air supply will meet the demands of the impact wrench.

Commercial impact wrenches often have a 1/2″ or even larger drive. That means it’s a bigger wrench, and that means more air will be required to serve it.

If just acquiring the impact wrench, be sure to review the manual and if the tool did not come with one, make sure to get the online version of the manual. It is important to know how much air that air tool uses (normally measured in CFM) and at what pressure that air must be delivered (normally measured in PSI).

With that information, and knowing that each HP of compressor motor will deliver around 3-4 CFM of compressed air at 90 PSI, it is possible to determine if the compressor is big enough to run the impact wrench satisfactorily.

Questions or comments? Please leave them below.