Air compressor for small shed shop

Because most people are doing more than operating one tool, and you don't want your motor running all the time. They're not designed for continuous use, especially the cheap ones. I use mine for impact wrenches, air ratchet, air chisel, da sander, paint gun, and even an air powered table saw. A few of these tools don't use much air, and some use a lot. When you're switching back and forth, it's nice to have a big tank so that you can maintain constant air pressure rather then relying on the motor all the time.

 

CFM rating should be at the motor to tank. Also note that there is a pressure associated with the CFM rating (i.e. 5 CFM at 40 psi, 3.5 at 90 psi). This is important because you want to make sure you have enough CFM at the pressure the tool needs. The higher the pressure gradient (atmospheric to tank pressure) the more power it takes to flow the same amount of air. One site I read on compressors quipped that a box fan can flow 1000 CFM, but the pressure difference is minimal. So know the pressures you will be using your tools at.

Also know that compressor ratings (like small engine ratings) are/have been inflated. A 120 V compressor cannot produce more than 2 HP (power is current X voltage and your wiring/voltage limits your current), which at best will flow 8 @ 40 and 6 @ 90 (CFM @ psi). A big tank helps for small jobs - you can charge it up and get more work done before it runs out, but to really get the compressor output for big tools/paint guns etc, 240 V compressors can produce 4 X the power of a 120 V compressor (twice the voltage and twice the current typically), or you have to go with a gasoline powered one (HP ratings between electric and gasoline do not line up 1:1...I think it's 1:2 - 1 HP for electric compressor = 2 HP for a gas compressor).

You might be able to find one used for a good price, but you have to be careful because if the tank is rusted out it could fail catestrophically. I think I have a similar craftsman to bigfitz (I'm going to assume the HP numbers were inflated, since mine is 120 V 2 HP - but I could be wrong) for $35 on craigslist, that was only a couple of years old, and only needed a wheel.

 

Air powered table saw? I've heard of air operated clamping devices etc, is the blade actually run by air?

 

Wouldn't be too hard. It would operate like an air drill. The air spins the arbor the blades attached to. Can't say I've seen one though.

Back on topic:

Look at the duty cycles on those motors. very few are 100% and I doubt any in your price range. thus the need for the larger tank.

 

So I'm still confused. iwingameover says "Also an important note with air rachets, air hammers, etc they don't work at their peak without the correct CFM. " but I hear from others that advertised SCFM numbers are inflated and that unless I go with a 240V or gas powered one I'm going to have too low SCFM.

I'm beginning to feel that the actual answer is "unless you're going to spend a fortune, get a decent sized tank so you can get your small-ish jobs done before the engine gets too far behind the pressure in the tank."

 

Yup. A guy actually gave it to me because it was old and he couldn't figure out how it worked. I found that there was a cracked air hose from the connector to the on/off valve. One trip to Home Depot and a whole lot of oiling and cleaning later, it was working fine. I've never taken the whole thing apart, but I just plug in my hose and keep the pressure at 90psi and let 'er rip. Pun intended.

 

Here's an example:

Look at this rachet: 3/8 craftsman from sears http://www.sears.com/shc/s/p_10153_1260 ... hets#specs

It says it has 50ft/lbs and 170RPM run down speed. It also requires 3.4SCFM at 90PSI.

With less pressure and less SCFM it will not develop 50 ft/lbs or it's 170RPM run down speed. It may well still turn and get the job done though.

Which back to my orinigal point of pick the tools you want to use and then pick a compressor to run them.

If you go here: http://www.aircompressorsdirect.com/com ... essors.php it has a wizard you can pick through and it'll recommend compressors for you. Also has alot of good explainations.

 

Boy, you got that right! The research alone to figure out what is what, and then to determine who is telling what truthes in their advertising claims, is basically a full-time job.

I've found these guys to be pretty honest, they'll also talk your ear off about their products if you call them...........they now carry air compressors:

http://www.badboyblasters.com/index.html

 

Good score pacocase. I've been a contractor for over 20 years and have never seen or heard of such a thing.

 

Sorry to hijack the thread with the chatter about my saw. To be honest, when I bought my compressor about 10 years ago, I went with the biggest 110v I could afford. I hadn't accumulated as many tools yet, but for future expansion, I figured that was the best policy. I ended up buying a 30 gal Craftsman with a vertical tank, and it has never let me down. There have been some times when I've been doing something really intensive like media blasting that I've wished I had a slightly bigger one, but the 30 gal is adequate for almost all jobs and doesn't take up that much space.

If you're just messing around as a shadetree mechanic, a 110v with a good oil less compressor and a medium-sized tank will make you very happy.

If you're a pro, and you're going to use it industrially, go with 220v or gasoline. These tend to only come with huge tanks - 60-120 gallons.

 

Ok feeling better about what to get now. Thanks to all for the input.