You need to consider the usage and demand of the compressor.

Tools require volume at pressure in order to run. If you are running a grinder that requires 8 CFM at 90 PSI to run, and your compressor is only rated at 5 CFM, it won't deliver enough air to run the tool worth a damn. If your compressor is capable of delivering 14 CFM at 90 PSI, and your tool needs 5 CFM, you're golden - it'll run fine.

Duty cycle is also an issue - a 30% duty cycle means the pump should only run 3 minutes out of every 10. A 100% or continuous duty cycle means it can run wide open forever.

Tools have listed ratings... see what you'll be running, match your tool (or go over that). If you're running two tools at once, say one that needs 8 CFM and one that needs 6 CFM, you need a compressor that will deliver at least 14 CFM to run them at the same time.

Larger tanks and higher tank pressures mean less pump time. The one I have in my shop is 25 gallons, 200 psi, and (I think...) 12 CFM. It runs grinders, smaller impacts, and a plasma cutter just fine for the little bit of use I put it through.

 

Here is a link to a model that I'm leaning towards.

http://www.aircompressorsdirect.com/...r/p85.html#q_a

 

That one is perfect for most home applications. Here is a quick link to give you an idea of what to look for:

http://www.ehow.com/how_2100364_buy-air-compressor.html

The key is knowing the tools you want to use on it. You want to make sure your compressor exceeds the requirements of your tools. Typically your paint sprayer or your impact are the ones to look at.

You'll find at 5.5 cfm you may be a little on the low side for the impact but as long as you have the pressure in the 20 gallon tank you just have to wait for it to build up. The sprayer in the other hand needs that continuous extra cfm as you can't wait for it to build up when doing a larger paint job, and changes in pressure drastically affect your finished product. I have to agree with Ranger on all aspects

CFM is cubic feet per minute. IE how many cubic feet per minute the compressor adds to the tank or how many a specific tool uses. Thing to keep in mind is that you use the pressure in the tank to do the work, not the compressor itself, the compressor's only job is to replenish the tank. If you can drain the tank quicker than you can fill it then you loose working pressure.

Hope this helps. FYI I just had to replace my 20 old Craftsman and bought a 30 gallon dewalt, love the thing as it's quiet and so far reliable, just wished I'd payed a bit more attention to my own advice and picked up one with a higher CFM rating.

 

Like I said, if you don't mind a little down time for the tank pressure to recover, almost anything will do .

Or maybe it's worth it to you to spend 200-400 bucks more to not need to deal with that. Or maybe you'll need to spend even more, depending on the air requirements of the tools you are using, and how continuously you want to use them .

 

Oh and I forgot about grinders check they use lots of air too.

 

Even just for that you'll want more than 20gal capacity, unless you like listening to the compressor running most of the time. I have a 35gal tank on my 110v compressor (oil-less, 150psi) in the garage, and if I'm yanking wheels off the car the compressor fires up to recharge the tank after 2 wheels. Don't misunderstand me, I'm not saying that it loses noticeable power at my impact guns, I can keep yanking wheels...it's just friggin loud 'cause the compressor kicked on. But my impacts go through enough air to warrant a refill after only 10 lugnuts apparently (at 90psi).

Now, when I'm using my die grinder...yeah, that thing sucks my compressor dry pretty quick. I often find myself grinding/cutting/etc for a couple minutes then letting the tank refill. Rinse, repeat.


Bottom line; even for the DIY garage, a 20gallon compressor won't cut the mustard. I'm looking for a 80gal minimum for my next tank.

 

thanks you guys. I appreciate the input. Looks like I'm going to be looking at the CFM. I would hate to finally get one of these things in my garage and be annoyed cause I didn't get one with more power.

My brother in law is going to pay for most of the cost (as a christmas gift) so i'm gonna chip with my own money and get one that's powerful enough.

thank you so much fellers. You guys rock!!!

Happy holidays !!!

 

Just to throw in my three cents... with the caveat that I've been out of the trades for a few years so some of my info might be dated.

First: Campbell Hausfield makes a shiat product. Not sure if there was an ownership change that brought this on... but they are pretty much selling Chinese and Indian pumps (but "assembled" in the US!) and depending on their reputation for quality.

Second: Husky (home depot) compressors are made my CH... so if price is important, you can buy the big red one and get the same product for less.

Third: Ingersoll Rand makes great compressors. Not cheap... but a quality (high end homeowner/mid range commercial) product.

Fourth: Per the advice of my Dad and lots of older guys I came up with... always buy as much tool as you can afford. You might not need it now... but you will someday. It's better to spend $1500 now than $500 now and $1500 later.

Fifth: DRAIN YOUR TANK!!!

Hmm... I guess that was a full nickel's worth of advice.

 

Be sure that no matter what, you look up every tool you will possibly ever wish to run and get the CFM rating for that tool. YOU MUST GET AN AIR COMPRESSOR THAT HAS MORE CFMS THAN THE TOOL. The tank size only affects how often the pump has to run and of course the less the better as it wears out the pump. Most cheap home units will only fill tires and sports ***** and will not run crap. 5 cfm's is not gonna get you much.

 

That's a great point. The CFMs is gonna be my main deciding factor. Thanks again boys!