Air tools are convenient time-savers, and can be fun when performing tasks like whizzing off lug nuts with an impact wrench. But, when doing bodywork, it's not just convenient to have an air compressor on hand, it's essential.
In the November 2012 issue of Car Craft, John McGann shared how, while working on a past project, his team's home air compressor couldn't keep up the air demands of their spray gun.
"We could 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 and 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."
John concluded that, to do the job right, get the biggest air compressor you can afford.
"Compressor horsepower ratings and tank volume are good selling points, but the real spec to be concerned with is the CFM rating. This rating refers to the volume of air the compressor can deliver at a given pressure, usually 90 psi."
Although the compressor he was using had a 9 CFM rating, it wasn't able to maintain enough air volume and pressure to power a sander or grinder for more than 30 seconds. Because it couldn't keep up, the pressure dropped to around 60 psi and the motor continuously kept running. Consequently, moisture from the air got into the tank and water began to spray out of the air line.
"You don't have to know a thing about painting cars to know that water in the paint will will ruin the paint job."
After careful research, the team decided upon the Central Pneumatic 5 Horsepower, 60 Gallon, 165 PSI Two Stage Air Compressor (the manufacturer recently changed its name from U.S. General). With a 15.8 CFM rating at 90 psi, this reliable two-piston compressor's got capacity to spare for a pro auto paint job, where the spray gun (the most demanding air tool) usually requires 12 CFM at 45 psi for proper performance.
The Car Craft team also installed a Central Pneumatic Industrial Air Filter Regulator, which manages air pressure and separates foreign matter and water, maintaining a steady 90 psi of dry, clean air, as well as Central Pneumatic 3' Lead Air Hose, capable of 200 psi working pressure.
Now the latest of a long list of car enthusiast magazines, Car Craft affirms the value and performance of the products at Harbor Freight Tools.