A pneumatic impact wrench requires a certain minimum size air compressor to work. But, how does one go about finding the right air compressor for his specific impact wrench? In this article, I’m going to try my best to help you get through this surprisingly complicated process by telling you what you need to know about air compressors for impact wrenches.
What size air compressor do you need for an impact gun?
Typically you need an air compressor with 4 to 5 CFM @90 PSI to run a 1/2 inch impact wrench. I would also recommend you to get a 20-gallon capacity compressor to avoid delay between tasks. You can refer the CFM chart at the end of this guide for other sizes.
Now let me explain why you need this minimum CFM and tank size.
How Much Air Pressure Does An Impact Wrench Need?
Air compressors are measured, at least in part, by how much air pressure (PSI) they produce and the flow of air (CFM). Even if you aren’t particularly familiar with air compressors, you can probably guess why air pressure is important. The more air pressure, the more powerful the tool. Likewise, the amount of air that flows is also important.
- CFM (Cubic Feet per Minute): This is the mass of air flowing per minute.
- PSI (Pounds per Square Inch): It is the unit that denotes the air pressure.
So, this raises the question of exactly how much air pressure and CFM you need for your specific impact wrench. The answer to this question will depend largely on what size impact wrench you are using. The larger the impact wrench, the more air that you need. There isn’t any sort of guide that you can apply for all the air tools. So instead, I will go through the most common impact wrench sizes. and tell you roughly which air pressure is needed to operate each size.
1/4-inch Impact Wrench
For a 1/4-inch impact wrench, you don’t need a lot of air pressure. An air compressor that delivers around 1 to 1.5 CFM (which stands for cubic feet per minute, the standard measure for air pressure) will be more than sufficient for an impact wrench of this size. You could go for more air pressure of course, but it isn’t necessary.
For a 3/8-inch impact wrench, you need a bit more power. More specifically, you need roughly double the power. So, be on the lookout for an air compressor with a power rating of around 3 to 3.5 CFM. Could you go lower? Maybe. For example, I could see an air compressor of around 2.5 CFM working out, but it would be cutting it close. If you are buying an air compressor specifically for your 3/8-inch impact wrench, I would definitely recommend shelling out the extra money to go for the 3 or 3.5 CFM air compressor.
Compressor for 1/2-inch Impact Wrench
If you are familiar with impact wrenches, then you know that 1/2-inch impact wrenches are probably the most common type of wrench. In terms of size, they are also directly in the middle of the size chart. So, it is important to find the right air compressor for this size wrench. Thankfully, you have a lot of options when it comes to air pressure. Anywhere from a 3.5 to a 5 CFM air compressor will be good for a 1/2-inch impact wrench. If I had to recommend a specific air pressure, I would say to play it safe and go for at least a 4 CFM air compressor.
On that note, I should also say that a 5 CFM air compressor would be my personal recommendation. It has a good balance of everything that you want in an air compressor.
Finally, I want to address the 1-inch impact wrenches. These are very uncommon and are typically only found on construction sites. Because of the size of these tools, you are going to need a very powerful air compressor to run them. I would say to look for an air compressor in the 9 to 10 CFM range. Obviously, that will be pricey, but if you are using a 1-inch impact wrench, then you are probably working in a setting where that kind of air compressor is needed often, so it is a good investment.Tip If you are working with frozen and rusted fasteners that require high torque, consider a 2 stage air compressor. A regular single-stage compressor can get you up to 125psi pressure whereas a two-stage system can deliver up to 175psi which can remove even the most stubborn nuts.
What size air compressor do I need for impact wrench?
While air pressure is important, it isn’t the only way to evaluate an air compressor. You also have to consider the tank size of the air compressor as well.
Impact wrenches are intermittent tools. That means unlike sandblasters or die grinders, you won’t be using an impact gun continuously for a long period of time. This means you can operate an impact wrench with a good portable electric compressor although a small pancake type would only work for nail guns.
Air compressors come in various sizes that are measured in gallons. The larger an air compressor is, the more air it can hold, which translates to more time spent working, and less time spent filling up your air tank. In short, when it comes to air compressor tank size, the larger, the better.
In my opinion, the minimum air compressor for impact wrench is 6-gallon one with 4 CFM. Any lower than that, you will really struggle to use the tool. Remember that this is the minimum size. I strongly recommend you buy one with a tank capacity of 20-gallon or more.
In general, you are going to want to balance cost against capacity. Air compressor with larger tanks may let you work for longer without any interruptions, but they are also going to cost a lot more.
I generally don’t use my impact wrench for long periods of time, so I’m perfectly content with a middle-of-the-road 10-gallon tank. That gives me enough air to do what I need to, without costing too much or taking too long to refill. However, I could easily see someone who works in a commercial setting needing a larger tank. If you do something like professional construction work, I would definitely recommend investing in a larger 20-gallon tank, maybe even a 30-gallon tank.
Will A 3 Gallon Air Compressor Run An Impact Wrench?
The short answer is No.
One of the more common types of home air compressor out there is the 3-gallon air compressor. These are very inexpensive and are often marketed as “beginner” or “starter” air compressors. So, a lot of people have them, and you may be curious if it can run an impact wrench. The answer is likely not.
Most 3-gallon air compressors are extremely weak when it comes to air pressure. Air pressure varies greatly, but in my experience, a 3-gallon air compressor will have an air pressure of around 0.5 CFM. As I said earlier, even the smallest impact wrench takes around 1 to 1.5 CFM to run reliably, so it likely wouldn’t be a good investment on your part. But more importantly, a 3-gallon air compressor will not provide a sufficient amount of air for the impact wrench to work reliably. You will be tired of constantly waiting for the compressor to refill the air.
Can a 6-gallon air compressor run an impact wrench?
The answer is yes, but I wouldn’t recommend it. In my experience, the smallest size air compressor that you need to run an impact wrench is 6 gallon. With a 6 gallon compressor, you should be able to work for a couple of minutes before you run out of stored air.
For instance, if you are removing the lug nut using an impact wrench with 6-gallon compressor, you should be able to pull out one wheel and then wait for 2 to 3 minutes. For the home users who occasionally use the air impact wrench, this may not be a big deal. If that is you then go for it.
CFM Chart: Impact Wrench Air Consumption
|Tool Size||Air Consumption||Pressure|
|1/4-inch Impact Wrench||2 CFM||90 PSI|
|3/8-inch Impact Wrench||3 CFM||90 PSI|
|1/2-Inch Impact Wrench||5 CFM||90-100 PSI|
|3/4-inch Impact Wrench||7 CFM||90-100|
|1-inch Impact Wrench||10 -16 CFM||90-125|
- Minimum Requirement: You will need a 3-4 CFM air compressor with 6-8 gallon tank.
- Recommended: Get one with 5-8CFM and a tank capacity of 20-30 gallons.
- Best: For professionals, you will get frustrated by the waiting time. If you are using multiple air tools I recommend you to get a 60 or 80-gallon vertical air compressor like this one from Powermate.