Pneumatic impact wrench

Richard Casto · **Posted:** Tue Apr 11, 2006 10:03 am

Adam Ligon wrote:

Charlie Smith wrote:

Actually, what I said is still an accurate statement. The CFM rating is the amount of air that the COMPRESSOR can deliver. Therefore, the same amount of air is being delivered to the tool for a 2 gal tank at 120 psi as a 200 gal tank at 120 psi (until the pressure drops lower faster on the smaller tank).

Charlie

Um no, thats not right. The pressure of the air may be the same for a moment, but the amount/volume of the air is vastly different between those two compressors.

In general I agree I don't know exactly how they measure the CFM values that you see advertised, but I tend to think that they measure the compresor/tank combo. That a given compressor may give slightly higher CFM with a larger tank. Why? I suspect that some of it has to do with the cooling effect of having a larger tank. That as you compress the air, it gets hot and IMHO I think this affects the CFM measurements in a bad way. So a larger tank radiates that heat faster than that of a smaller tank. Lowes has two identical 7HP/60gallon units with one difference. One has an intercooler between the compressor and the tank. The one with the intercooler is rated at 13 CFM @ 90 and the other is rated 10 CFM @ 90.

Still these are slight differences and the power of the compressor motor is a huge factor. 110V units can only generate so much power at a given amperage vs a 220V unit. Which is why you only see the higher CFM on the 220V units

Charlie Smith · **Posted:** Wed Apr 12, 2006 8:19 pm

Adam Ligon wrote:

Charlie Smith wrote:

Actually, what I said is still an accurate statement. The CFM rating is the amount of air that the COMPRESSOR can deliver. Therefore, the same amount of air is being delivered to the tool for a 2 gal tank at 120 psi as a 200 gal tank at 120 psi (until the pressure drops lower faster on the smaller tank).

Charlie

Um no, thats not right. The pressure of the air may be the same for a moment, but the amount/volume of the air is vastly different between those two compressors.

My whole point was if you unplug the compressors, it does not matter how big the tank is until the pressure drops (which it will obviously do quicker in the small tank).

That has been my point all along. I didn't know we were going to argue fluid mechanics though...

Chuck Frank · **Posted:** Sat Apr 15, 2006 12:40 am

If you don't want to spring for a bigger compressor, buy yourself a Milwaulkee 18V cordless 1/2" impact wrench like we did. It has the torque of the good air powered ones and you can justify the 300.00 price the first time you change tires at an AX with it. We've changed 16 sets of tires in one weekend on one battery charge with ours. Highly recommended!

ColinOConnell · **Posted:** Sat Apr 15, 2006 10:27 am

Chuck Frank wrote:

If you don't want to spring for a bigger compressor, buy yourself a Milwaulkee 18V cordless 1/2" impact wrench like we did. It has the torque of the good air powered ones and you can justify the 300.00 price the first time you change tires at an AX with it. We've changed 16 sets of tires in one weekend on one battery charge with ours. Highly recommended!

Yeah, that's on my 'I want' list. It's only money right?

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Pneumatic impact wrench

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