Compressor / Tool Compatibility

How long do you need to use it continuously? You can run a huge grinder on a small compressor, but you'll have to stop after ~30 seconds to let it refill. If you need it 100%, go with the 12 CFM compressor.

I wish pneumatic tool manufacturers would be more specific and consistent in their ratings (i.e. no throttle pressure is specified and it is not clear if the cfm is referred to standard conditions, e.g. scfm). In any event, I think you should use the larger number when comparing to compressor capacity. I suspect that the 3 cfm is either referred to some throttle pressure or is an "average" consumption considering that the throttle will likely not be open continuously. If it is an average, in your case it means that the tool can be used for only 25% of the time, which is unspecified, in order to keep the consumption down to an "average" of 3 cfm. The @ load likely means the consumption when the tool is under full rated load and not spinning free. The free speed rpm and the air consumption would be greater still with no load on the tool. That's my best guess given only that information.

Rod