How Big of a Compressor do I Need for Air Tools?by K.K. Lowell
Air tools are time and labor savers. Used in the home or small shop they help make better and faster repairs. Each tool needs an adequate supply of compressed air to operate it and a compressor should be sized according to the tool's air needs.
An air drill with a 3/8-inch chuck capacity will require 4 to 7 cubic feet of air per minute (CFM) to operate. An air-powered drill with 1/2-inch capacity will require 6 to 8 CFM at 90 pounds per square inch (PSI).
A grinder with the power to operate a 7-inch grinding disc will use an average of 7 CFM at an air pressure of 90 PSI.
One of the more common air tools is the air chisel. It requires an average of 4 to 8 CFM at 90 PSI. Needle scalers are similar tools and require the same approximate CFM.
The most commonly used mechanic's air tool is the impact wrench. For automotive use, a 1/2-inch drive impact wrench is the most popular and will require about 5 CFM. Larger 3/4-inch wrenches for truck use require 8 to 11 CFM for proper operation. A larger air hose is also required.
Sizing the Compressor
While CFM delivery is of primary importance, the maximum pressure and storage tank size are important also. Select a compressor with a CFM output at least 25 percent greater than what is required by the number of tools which will be operated at the same time. If given a choice, buy your shop compressor with the largest tank capacity available.