Compressor/Tool specs.????

[johno]

I've been toying with the idea of getting a paint gun to do some small part painting, and here's my problem.
Lets say gun requires 4cfm at 40psi, (i'm picking all numbers out of the air here)

Compressor states it delvs. 7.5 cfm at 90lbs. " " "

Is that good,bad, does it do the job?? How do I relate the demands of one to the output of the other when the ratings are measured differently? Not just the numbers I stated which I made up, but a general rule for future items.

Thanks for any info.

 

[koditten]

You have your specs for the compressor skewered. There should be a CFM (cubic foot per minute) rating for the compressor. More than likely there will be 2 listings. One for high pressure and one for low pressure.

For example the specs for the compressor will say 12 cfm @ 100 psi and a low pressure of 17 cfm at 65 psi.

Most paint guns will have the volume (cfm) needed to function listed on the box. One other thing, the cfm listed on spray guns is an average. You can change the amount of air pressure and cfm needed by how thick you mix your paint. Thicker paints need higher pressure and volume.

Kirk

 

[johno]

You have your specs for the compressor skewered. There should be a CFM (cubic foot per minute) rating for the compressor. More than likely there will be 2 listings. One for high pressure and one for low pressure.

For example the specs for the compressor will say 12 cfm @ 100 psi and a low pressure of 17 cfm at 65 psi.

Most paint guns will have the volume (cfm) needed to function listed on the box. One other thing, the cfm listed on spray guns is an average. You can change the amount of air pressure and cfm needed by how thick you mix your paint. Thicker paints need higher pressure and volume.

Kirk

Kirk thanks for answer, I went back and changed psi to cfm, so maybe it will make more sense now.
Am I correct in assuming from your answer that a compressor produces higher cfm at lower psi??

 

[Jack Olsen]

Kirk thanks for answer, I went back and changed psi to cfm, so maybe it will make more sense now.
Am I correct in assuming from your answer that a compressor produces higher cfm at lower psi??

Yes. Although the higher (low pressure) rate is usually there just to make the machine seem less anemic. The number you want to pay attention to is the compressor's CFM at 90 psi. That's the pressure you'll be operating most tools at. Overall high pressure (120, 150, whatever) are less important (but not unimportant). Rated HP is usually optimistic. CFM is what matters -- it's how much pressurized air the machine is able to get to your high-appetite tools.