Garage Air Compressor
Article by Mark Trotta
Having an air compressor allows you to use air tools, which deliver higher torque and are more powerful than traditional electric tools. They also decrease the amount of time spent on a project.
Sanding, cutting, grinding, painting, polishing, and inflating - a garage air compressor makes all these chores easier and less time consuming. And when you're done, snap on a blower attachment and clean the mess quickly.
Air Flow vs Air Pressure
Compressors are rated by SCFM (standard cubic feet per minute), which is the amount of air it can deliver when running constantly. Flow and pressure are inversely proportional, so as the pressure goes up, the flow will go down.
To determine how to choose the best air compressor, consider the tools you will be using. Equipment that uses compressed air should have a rating of flow and pressure that it needs. This information will be in the manual, or go to the manufacturer's website. The listing below is just a sampling.
Air Compressor Ratings
Air tools are often rated as 'Average CFM' which is based on a 25% duty cycle (15 seconds out of a minute). If you will be using an air tool on a continuous basis, such as an orbital sander or die grinder, multiply the Average CFM by four. This will give you a continuous CFM rating for the tool. Look at the "delivered" CFM rating, not the CFM "displaced" rating.
The more horsepower (and larger air tank) the compressor has, the better it will do at higher psi settings. This would include die grinders and air hammers. Buy a compressor that can keep up with your tools.
Oil-Lubricated vs Oil-Free
Oil-free motors run louder. With my old Sears compressor I wore ear plugs when it was running. An oil-lubricated cast-iron compressor will last a longer time than an oil-free unit. If you're just running air tools, oil-lubricated is a better choice, but not for painting (oil contamination).
220-Volt 26-Gallon Compressor
Currently, my garage air compressor is a Campbell-Hausfeld 26-gallon, 220v unit. The motor is cast iron, oil-lubricated, and rated at three running horsepower. It's been great for pretty much any kind of air tool I need, including air ratchets and air hammers.
Shop: Campbell Hausfeld 20-Gallon Air Compressor
I placed the compressor next to my workbench for convenience, and it's loud when it's filling up, so I slip on hearing protection while it's running.
Single-Stage vs Two-Stage Compressors
Single-stage units are smaller and louder, cycle more often, and are less expensive. Two-stage compressors are not really necessary for home garage, but they are quieter, cycle less frequently, and deliver lots of continuous pressure. Most of the noise is a low frequency thumping sound.
For a low to medium use, single-stage air compressors work well. Most are 110v and can be plugged right into the wall. If you are going to use it for cut-off wheels and grinders that's fine, but if your planning on sandblasting with a pressure blaster it will mostly likely not keep up.
Shop: Ingersoll-Rand 30 Gallon Air Compressor
The Ingersoll-Rand SS3F2-GM Garage Mate is rated at two-horsepower, has a 30 gallon tank, and features an oil-lubricated motor.
Large two-stage compressors are for medium and heavy use. If you are constantly using air tools, this is what you need. They are built to run more often and keep higher pressure. If you're serious about automotive restoration, consider a 220v unit with a dual-stage motor. Pay a qualified electrician to run a 220v outlet into the garage, especially if you plan to weld anything more than sheet metal.
Vertical vs Horizontal Compressors
Horizontal tanks will fill quicker, but the motor will cycle on and off more often with prolonged use. If you're using a die-grinder or other constant-duty air tool, they'll run longer and may overheat the motor.
Shop: Porter Cable 30-Gallon Air Compressor
The Porter Cable PXCMLC1683066 is a vertical 30-Gallon single-stage air compressor. Generally, air compressors that have vertical tanks are offered in larger sizes and take up less floor space, but they are not as easy to move around.
Air Compressor Oil
Compressor oil should be changed regularly. Since compressor oil has additives that are not necessarily found in automobile oil or other oils, only use oil that is clearly labeled as compressor lubricating oil. Conversely, the additives that are in other types of oils may damage your air compressor. For the DIY type air compressor user, follow the manual guidelines, or change the oil once a year.
Your compressor needs air flow around it to prevent overheating.
Avoid enclosed areas such as under workbenches.
Air Hoses and Fittings
The most common air hose is 3/8" rubber. These are fine for a single or two-car garages. For painting, a larger 1/2" air hose will give more volume. For a big shop, consider permanently installed rigid air lines.
Shop: Garage Air Hose
With all air compressors, air hoses and tools connect with quick-disconnect couplings. These fittings come in many styles, and they connect the female end on the hose to the male end on the tool. Use Teflon tape on the male fittings for airtight joints.
CFM Requirements For Air Tools
- 1/4" Ratchet: 2.5-3.5 CFM
- 3/8" Ratchet: 4.5-5 CFM
- Air Hammer: 3-11 CFM
- Mini Die Grinder: 4-6 CFM
- Cut-Off Tool: 4-10 CFM
- 7" Angle Disc Grinder: 5-8 CFM
- Dual-Action Sander: 11-13 CFM
Read: Best Automotive Air Tools
Air Compressor For Automotive Painting
Smaller compressors will have more trouble with moisture buildup than larger ones. Any restriction in the air line reduces air flow. This is a major concern if you're considering painting your car yourself. A paint gun has a higher duty cycle than an impact wrench or an air ratchet, so the amount of air used is higher.
Read: Best HVLP System For Automotive