How Big of An Air Compressor Do I need for a Nail Gun?

How does an air compressor work and types?

The working principle of an air compressor largely depends on the types of air compressors. However, the basic principle of an air compressor is to pull air, pressurizes it, and store it inside a tank. When the tank's pressure reaches its maximum permissible limit, the air compressor stops working. The compressed air, then, is stored in the tank until needed to use it.

Now the question is, how does the compression happen? Well, since there are various types of compressors, the answer will vary depending on the mechanism used to compress the air.

Broadly there are two types of air compressor –

• Positive Displacement, and 
• Dynamic.

Positive Displacement Compressor can be divided in two class -

• Rotary Screw Compressor and
• Reciprocating compressors.

Rotary screw air compressors are the easiest types of air compressors. It has an internal cooling system and doesn't need much maintenance. Where need continuous operation with high capacity (5hp to 350hp), a rotary screw is the best suited there.

Rotary screw air compressors generate energy through two internal rotor spinning opposite directions. The air is getting stuck between the two reverse rotors, and the pressure rises inside the housing.

The reciprocating air compressor, also known as piston displacement compressor and extensively uses at different small scale works such as garages and home construction projects.

It works just like internal combustion engines, using the movement of piston down-and-up to compress air, store it in a tank, and release when needed. Reciprocating compressors are available in single or multi-stage variations, which regulates the ranges of pressure they can generate.

Dynamic compressors can be divided into two class again -

• Centrifugal compressor, and 
• Axial compressor.

Centrifugal air compressors are using a diffuser to build up potential energy from the air. It has a multi-stage compression system, due to which it can produce a high amount of energy with a relatively small machine. It often uses in large industries like chemical plants or steel manufacturing factories.

Axial air compressors are also high capacity and not use in even construction sites. Usually, it is seen to be used in high-speed engines like ships or planes.

From the above classification, we may conclude that the reciprocating air compressor or piston air compressors are the kinds that suitable for small machines. And will also be better suited for the air nail guns.

Let's see the video below to get a glimpse on how do air compressors work – 

What is the optimum Flow Rate - CFM

CFM shows you how fast the air flows from the compressor to the device. It is, therefore, important to check the air compressor CFM before purchase. If the airflow rate of your compressor is lower than the system requirement, you'll have to stop working and wait until the kickback of the compressor.

Here, CFM stands for cubic feet per minute, which means the volume of air moves or flows from one place to another at a particular time.

The general formula of calculating the CFM is as follows –

1. Measure the volume of space in cubic feet. Fill it up with air.
2. Then determine the time of the evacuation of the space.
3. Then divide the volume by time.

Example: Suppose the size of the room is 1000 ft3, and it's full of air. Then it takes five minutes to evacuate the room through an orifice. So the flow rate will be 200 CFM.

Volume (1000 cubic feet)/time (5 minutes) = 200 CFM

However, in the case of nail guns, we no need to follow this intimidating task as the manufacturers predetermine it. Yeah! All the nail guns manufacturer has a recommended CFM. What you need is to calculate the size of the air compressor by matching it with them.

There is simple math again. Multiply the recommended highest CFM rating of your pneumatic nailer by 1.5, that's it. Suppose the CFM for framing nailer is 2.2, then the required size of the air compressor will be 2.2x1.5 = 3.3 CFM.

So, the recommended CFM for framing nailer is 4. Here, this additional CFM gives you a guarantee that the compressor will work efficiently and required less time to refills.

Let's check the chart below to get the nail gun vs. recommended CFM.

Now, we get the CFM for the nail guns. But to choose the perfect air compressor, we have to pass some other criteria too. Our next subject is to know about air pressure or PSI.

What is the relationship between PSI and CFM?

The unit for calculating the air pressure is the PSI (pound per square inch). We can calculate the PSI by measuring how many pounds of pressure actually exerted on a single square inch of the area — 10 psi is equal to 10 pounds of force per square inch applied.

PSI is the amount of force an air pressurizer can deliver. PSI has a strong impact on CFM or SCFM. If you lower the PSI, the flow rate CFM will go high. On the other hand, higher PSI means that the compressor can hold more air in the tank, enabling the air tools to run longer.

A higher CFM level compressor with optimum air pressure can produce more air and is best suited for heavy-duty applications, such as running air wrenches and framing nail guns.

For a pneumatic framing nail gun, the minimum required pressure is 90 psi, and 2.2 CFM. So, to run a framing nailer, you must pick an air compressor that can produce at least 4 CFM @ 90 psi.

Is HP a matter for air compressor?

You may know that HP is the abbreviation of Horsepower, which indicates the engine's working capacity. Similarly, the HP of the air compressor indicates the total power of the engine. It determines, in simple terms, the amount of work that the air compressor can do within a given amount of time.

If you determine the right air compressor with tank and CFM rating, you will automatically get the correct HP. So, it need not worry much about the HP of an air compressor like CFM or PSI.

You would think that maximum efficiency would be given by the more HP an air compressor has. But not all of this is real. HP isn't the only factor influencing the output of compressors. If a 5HP and 10HP compressor provide the same PSI at a constant flow rate, then the 5HP compressor will be going to be more economical.

So, doing more with less HP can save you money and result in greater returns over the lifetime of the compressor.

What is the right tank size for nail gun?

On the other side, bigger tanks can carry extra compressed air at higher pressure. These are, therefore, ideal for operating larger projects, such as automotive work and steel manufacturing plants, where required continuous airflow.

Portable or stationery: Which one is best for nail guns?

Due to the nature of the work, a portable air compressor is best for nail guns. Nail guns, like framing nailers, need to do both outdoor and indoor framing, decking, and more with it. And to attach fiberglass shingles on the rooftop, or siding on framing need a roofing or siding nailer. So, if your compressor didn't reach those remote places, you certainly didn't finish your project.

So, for convenience, you should choose such an air compressor that is not bigger. At the same time, it meets all the CFM and PSI requirements to drive nails smoothly too. Therefore, a compressor of 6 to 10-gallon tank size is okay for running 3/4 nail guns without any issue and portable enough to easy maneuverability.

However, if you are planning to run multiple tools like an impact wrench, an air spray brush, a ratchet, or a sanding machine simultaneously and portability is not an issue, you may choose a big stationary air compressor.

Additional Features of an air compressor to look for:

​In addition to the basic specifications, there might also be some additional features you are looking for when choosing an air compressor:

Air cooling system

The air compressors generate a certain amount of heat during compression of air. Now, if your compressor doesn't have enough arrangement to keep the machine cool, it can shorten life, even causing an accident. So, check the cooling system before purchase.

Thermal Protection

While air compressors come with a cooling system to protect the machine from being overheated, long-term use can result in malfunction. A thermal protector works automatically to stop the device to secure the compressor from catch fire. So, your air compressor must have thermal protection.

Noise level

Once you switch on the compressor, you cannot avoid noises, as it is one of the louder machines around us. However, some modern compressor comes with a low noise level. Try to check the dB level of the compressor before purchase if you really hate those sounds. Sorry, who not hate the sound created from a machine like compressors? 

Oil-free operation

Practically all of the contemporary small air compressors are oil-less, meaning no more worrying about checking or pouring oil. Less oil means less frequent servicing needed. An oil-free air compressor, however, has a shorter life than lubricated ones.

Conclusion:

When you plan on pursuing woodworking as a career and want to create a big workshop for potential growth, then the smart choice would be to select a large-capacity air compressor. On the other hand, if DIY is on your mind, a small pancake-style air compressor is good enough. So, the size of an air compressor for a nail gun depends primarily on your strategy and budget.

More Queries to Answer:

Is higher CFM a better air compressor?

CFM and PSI exist a correlation. If PSI goes down, then CFM will go up. And PSI's necessary to properly drive the nails. Nail guns usually required air pressure of up to 120 psi. Therefore it is easier to use a higher CFM air compressor to control the air pressure. For a framing nailer, it is safer to have four or higher CFM to get optimum pressure to drive nails into wood precisely.

What kind of air compressor do I need for a nail gun?

A pneumatic nail gun is an intermittent power tool, which means it does not require a continuous air supply. Instead of that, a short burst of air is necessary to sink the nails into the wood. So, a portable air compressor with a rating of at least 2 CFM and a capacity of 2 to 6 gallons is good enough to operate a pneumatic nail gun.

Can an impact wrench run on a 6-gallon air compressor?

Of course! It may. But, you know, the minimum airflow requirement to operate an impact wrench is 6-gallon. And using an exact match compressor wouldn't be a good idea, because you'll be out of the air in a short time and need frequent refilling.

As per the pro advice, it is wise to use a compressor that is 1.5 times higher than the capacity required by the device.