How to Choose the Right Air Compressor

This is what we were trying to paint April’s car with. It’s a 5.5hp (peak, 1.7 sustained) Husky air compressor we bought at a garage sale for $75. It has a light-duty, oil-less compressor pump mounted on a 32-gallon tank.

This is what we were trying to paint April’s car with. It’s a 5.5hp (peak, 1.7 sustained)

For the most part, air tools are a convenience, a great time saver. It’s fun to buzz lugnuts off with an impact wrench, and air ratchets make quick work of a variety of underhood or undercar jobs, but you certainly don’t need them for the majority of mechanical work you’ll be doing on your car. If you’re doing bodywork, however, air tools are a necessity, and having a good air compressor is paramount to getting the job done.

We speak from experience, too. We were never able to finish the paint job on the ’64 El Camino in our last paint and body issue (Apr. ’12) because our home air compressor wouldn’t keep up with air demands of the spray gun. We could only spray for about a minute before the air pressure began to drop, and when that happens, the spray pattern changes and becomes inconsistent, and we’d have to stop to wait for the compressor to charge back up. When spraying a solid color enamel, painting the car panel-by-panel is possible, but metallics and pearls need to cover the car all in one coat. If not, the pattern of the effects will vary from one panel to the other. In short, when painting a car, you need a compressor that is able to provide enough air pressure and volume to spray the whole car in one pass. The short answer is to buy the biggest air compressor you can afford, but there’s more to the story than that.

Compressor horsepower ratings and tank volume are good selling points, but the real spec to be concerned with is it’s cfm rating. This rating refers to the volume of air the compressor can deliver at a given pressure, usually 90 psi. Though our garage-sale compressor is rated to deliver 9 cfm of air, it could not maintain enough air volume and pressure to power a DA sander or angle grinder for more than half a minute before running out of steam.
Compressor horsepower ratings and tank volume are good selling points, but the real spec t
When pressure in the tank drops, the pump switches on to try to maintain a certain amount of pressure. It couldn’t keep up with most of our autobody tools; pressure would drop to about 60 psi, and the pump would run continuously. Obviously, this is bad for the pump motor, but it’s also bad for your tools. As it is pressurized, moisture in the air is literally squeezed out and collects in the tank. The more the pump is running, the more the tank fills up. If the motor is running continuously, instead of dropping it to the bottom of the tank, water will start to spray out of the air line. You don’t have to know a thing about painting cars to know that water in your paint will ruin the paint job.
When pressure in the tank drops, the pump switches on to try to maintain a certain amount
You can remedy this with an air separator, but even that can only catch so much moisture. Water in the air stream easily overpowered this inline moisture separator.
You can remedy this with an air separator, but even that can only catch so much moisture.

Description	P/N	Source	Price
60-gallon air compressor	93274	Harbor Freight	$899.99
3/8-inch lead hose	91294	Harbor Freight	3.99
Air filter regulator	68247	Harbor Freight	37.99

Our solution came via Harbor Freight Tools’ 60-gallon air compressor. With a 15.8-cfm rating at 90 psi, it will provide enough capacity to run our spray guns, which typically require a continuous 12 cfm of air at about 45 psi to operate properly and are our most demanding air tool. If you match the compressor according to the demands of your highest-consumption air tool, you’ll be fine.
Our solution came via Harbor Freight Tools’ 60-gallon air compressor. With a 15.8-cfm rati
The two-piston pump is driven by a 5hp electric motor that operates on 220V power. We had to wire our junction box with a 30-amp breaker, wire in an outlet, and make a plug, which also added to the overall cost of the compressor.
The two-piston pump is driven by a 5hp electric motor that operates on 220V power. We had
We also installed Harbor Frieght’s wall-mounted regulator and water separator. This maintains a steady 90 psi of clean, dry air to our tools.
We also installed Harbor Frieght’s wall-mounted regulator and water separator. This mainta