PSI Technic — Compressed-air pressure setup for | psitechnic.com
Match CFM at 90 psi and tank volume to the tools you actually run — the 25% headroom rule does the arithmetic.
Compressors are compared by CFM — cubic feet per minute — quoted at a pressure, and the standard rating point is 90 psi because that is where most tools are rated. A CFM figure without a pressure attached to it says very little.
The working rule: a compressor should deliver at least 25% more CFM at 90 psi than the tool draws. The headroom covers line losses and keeps the compressor from running flat-out against a tool that never stops asking for air.
A worked example with the commonest hungry tool: a 1/2-inch air impact wrench typically draws about 2.5-5 CFM at 90 psi. Multiplied by 1.25, the compressor should be rated for roughly 3.1-6.3 CFM at 90 psi. Below that, the wrench feels strong on the first bolt and weak by the third.
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Tank volume answers a different question: how long the compressor can supply air before the motor has to cycle again. Standard workshop compressors cut out between 125 and 175 psi of tank pressure, and a larger tank stretches the time between those cycles. It does not increase CFM — a tool that runs continuously, like a grinder or a spray gun on a large panel, needs compressor output, not just storage.
Duty cycle is the practical ceiling: a compressor that must run without pause to keep up with a tool is undersized for that tool, whatever its tank says. Intermittent tools — nailers, blow guns, inflators — forgive a small compressor; continuous tools do not.
Build the requirement from your tool list: take the CFM draw of the hungriest tool from the Air Tool Pressure and CFM Chart, multiply by 1.25, and that is the minimum compressor rating. Then set it up with the procedure on How to Set an Air Compressor Regulator.
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