Garage Air Compressor
Air tools 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.
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 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.
Vertical vs Horizontal Compressors
Generally, garage air compressors that have vertical tanks are offered in larger sizes and take up less floor space, but they are not easy to move around. 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.
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).
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.
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.
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Air Compressor Oil
Compressor oil should be changed regularly. Only use oil that is clearly labeled as compressor lubricating oil. Compressor oil has additives that are not necessarily found in automobile oil or other oils. 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
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.
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.
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
Currently, my garage air compressor is a 26-gallon, 220v Campbell-Hausfeld unit. The motor is a cast iron, oil-lubricated, twin cylinder, and rated at three running horsepower. It's been great for pretty much any kind of air tool. I placed it next to my workbench for convenience.