I'm looking into getting Craftsman air tools (3/8" ratchet and 1/2" impact wrench), but I need help with the compressor. If the ratchet and impact wrench SCFM use at 90 PSI is 4.0 SCFM, then do I need a compressor that puts out 4.0 SCFM at 90 PSI?

I ask because most of the Craftsman compressors for less than $200 are rated at around 2.5-3.5 SCFM at 90 PSI. The cheapest one I can find that puts out more than 4.0 SCFM at 90 PSI is $300.

 

The rating is continuous use. With things like impact wrenches and wratchets you are rarely using it for more than short intervals.

The pump fills the tank and you use the air in the tank for the tools. The larger the tank, the longer you can work until the pump needs to recharge. Once the pump comes on the CFM rating comes into play as a measure of whether it can keep up with your work - or how long it will take to recharge the tank if you have to stop work.

I would personally rather have a compressor with a smaller CFM rating and a larger tank than the other way around. It's the tools like sanders and grinders that really give it a workout since they have high draw and you tend to use them for extended periods.

 

What size tank would be adequate then?

 

I would shoot for 20-30 gallon *minimum*.

Scott

 

20-30 gallon will work fine for impact wrenches, rachets, and occassional grinding. It probably will be inadequate for painting or sustained grinding/sanding.

 

i've got a 30 gallon in the gayrage... it is sufficient, but not ideal... for topping off the tires? great. for suspension work or cutting wheel work, i could use a bigger tank.

i hate sitting there waiting for it to fill back up... also, if you live in a townhouse you may want to consider what time you do your work. i often do my stuff late at night and i simply can't run the compressor because it is too loud... a lot of times i just have to quit working for the night when i run out of air (no way i'd use hand tools )

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by MichaelJComputer &raquo;</TD></TR><TR><TD CLASS="quote">also, if you live in a townhouse you may want to consider what time you do your work. i often do my stuff late at night and i simply can't run the compressor because it is too loud... a lot of times i just have to quit working for the night when i run out of air (no way i'd use hand tools )</TD></TR></TABLE>

Very true. The oil-less compressors in particular are very noisy. The oiled compressors are quite a bit less noisy, but usually cost more and come attached to larger tanks.