Tool review: Portable Air Compressors
We tested 11 units priced from $130 to $325 in search of one that will handle most woodworking-shop needs.
A portable air compressor won't cut, shape, or join wood, but it's one of the handiest tools you'll ever own. You can use it to power pneumatic nailers and other tools in your home, shop, or job site; to inflate all sorts of things; and to blow away wood debris. We like the 3- to 6-gallon size for its all-around usefulness, ease of moving from place to place, and affordability.
Nailers? No problem. Sanders? Sorry.
Each of the tested compressors easily powered a brad nailer, finish nailer, roofing nailer, and framing nailer as we drove nails into dimensional pine lumber. To our surprise, all the compressors maintained the required air pressure for our one-nail-per-second testing pace--even with the framing nailer shooting 3-1/2" ribbed nails! In fact, we emptied the nailer's magazine of finish and roofing nails as each compressor's pump kept the tanks supplied with adequate pressure. Only the 3-gallon Husky H1503TP ran out of the pressure needed to drive a full magazine of framing nails at that pace--but it still sank 65 nails before we had to stop and wait for it to replenish the tank.
Next we used each compressor to spray polyurethane finish with a 600cc gravity-fed spray gun. The best units could spray two minutes before falling short of the requisite air pressure--not long enough for medium- and large-size projects. However, you can successfully spray small projects with one of these compressors if you switch to a detail sprayer with a 100-200cc cup that requires less air volume.
If you plan to run a pneumatic sander, impact wrench, or large spray gun, get a 30-or-more-gallon-capacity stationary compressor. The compressors we tested simply lack the air storage and pump capacity to power these air-hungry tools.
Just because an air compressor pump will run continuously as long as there's demand doesn't mean it should. Each compressor has a "duty cycle," the manufacturer's rating for how long its pump should run. For example, if your unit rates at a 50 percent duty cycle, it should not run more than half of the time you use it. If it exceeds that limit it could overheat and shut down; you need a larger compressor. Four of the models rate as continuous duty, meaning they can run nonstop without overheating. All of these have oil-lubricated motors--more on that next.
The 11 compressors we tested have either oil-lubricated pumps or oil-free pumps. Oil-lube models feature an induction motor with either a cast-iron or aluminum pump housing and twin-stacked tanks. These units run 2-4 times quieter than the oil-free units and generally have less tank capacity, but weigh about twice as much. You'll also need to change the oil a couple of times a year.
Most oil-free compressors have universal motors and a single pancake-style tank. (The oil-free Ridgid OF50150TS has an induction motor and three stacked tanks.) With the lighter weight of the pump and motor comes a lighter price, up to a third less.
Also consider your electrical supply in choosing between the two types of compressors. Oil-lube models require more amps at start-up. Four tested units (Bosch CET3-10, Hitachi EC12, DeWalt D55151, and Senco PC1131) require a 20-amp circuit; those models would not start on some 15-amp circuits in our tests. And, the Bosch and Hitachi failed to start in a 30°F garage. So if you routinely work in a cold environment, opt for an oil-free compressor.
If the ability to lift, carry, and transport your compressor matters, here's where you can quickly pare your list of potential purchases. The oil-lube models weigh 20-40 pounds more than the oil-free pancake units, and their designs make them more difficult to carry because they're typically not balanced well. The Ridgid, though oil-free, tops our test at 77 pounds. But the 74-pound Makita MAC2400 proved the most difficult to carry because it's more stretched out with the handle in the center.
Ridgid offsets its weight by breaking down into two smaller units, as shown. After using it with all three tanks connected, simply unhook the pump and 1-gallon tank from the two larger tanks. Carry one unit in each hand and it doesn't seem as heavy or cumbersome overall. We found the smaller module great for such jobs as nailing up trim in a house or inflating a flat tire, where you don't need the larger tanks' storage. And because each unit has its own valves and hose connections, you can also use the two larger tanks to transport air when you don't need the pump.
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